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Microbial strategies for bio-transforming food waste into resources

Poonam Sharma, Vivek Kumar Gaur, Sang-Hyoun Kim, Ashok Pandey

PII: S0960-8524(19)31810-3
DOI: https://doi.org/10.1016/j.biortech.2019.122580
Reference: BITE 122580

To appear in: Bioresource Technology

Received Date: 1 October 2019

Revised Date: 6 December 2019
Accepted Date: 6 December 2019

Please cite this article as: Sharma, P., Gaur, V.K., Kim, S-H., Pandey, A., Microbial strategies for bio-transforming
food waste into resources, Bioresource Technology (2019), doi: https://doi.org/10.1016/j.biortech.2019.122580

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 Microbial strategies for bio-transforming food waste into resources

Poonam Sharmaa¶, Vivek Kumar Gaurb,c¶, Sang-Hyoun Kimd and Ashok Pandeye,f*
a
Department of Bioengineering, Integral University, Lucknow, Uttar Pradesh, India
b
Environmental Biotechnology Division, Environmental Toxicology Group, CSIR-Indian

Institute of Toxicology Research, Lucknow, India

c
Amity Institute of Biotechnology, Amity University Uttar Pradesh, Lucknow Campus, Lucknow,

India.
d
School of Civil and Environmental Engineering, Yonsei University, Seoul, Republic of Korea
e
Centre for Innovation and Translational Research, CSIR-Indian Institute of Toxicology

Research, Lucknow, India

f
Frontier Research Lab, Yonsei University, Seoul, South Korea

*Corresponding author. Email id: ashokpandey1956@gmail.com

¶ Both the authors contributed equally.

1
Abstract

With the changing life-style and rapid urbanization of global population, there is increased

generation of food waste from various industrial, agricultural, and household sources. According

to Food and Agriculture Organization (FAO), almost one-third of the total food produced

annually is wasted. This poses serious concern as not only there is loss of rich resources; their

disposal in environment causes concern too. Food waste is rich in organic, thus traditional

approaches of land-filling and incineration could cause severe environmental and human health

hazard by generating toxic gases. Thus, employing biological methods for the treatment of such

waste offers a sustainable way for valorization. This review comprehensively discusses state-of-

art knowledge about various sources of food waste generation, their utilization, and valorization

by exploiting microorganisms. The use of microorganisms either aerobically or anaerobically

could be a sustainable and eco-friendly solution for food waste management by generating

biofuels, electrical energy, biosurfactants, bioplastics, biofertilizers, etc.

Keywords: Food waste, Valorization, Biofuels, Bioplastics, Electricity

2
Introduction

Food is an essential component for the survival and existence of life. Organisms at different

evolutionary levels consume food in different form viz. micro-organisms ingest in the form of

macromolecules like carbohydrate, fats, nitrogenous compounds, vitamins and minerals

contrastingly higher eukaryotes like humans feed upon a complex version of food i.e. in the form

of fruits, vegetables, cereals, pulses, meat, and dairy products. A major concern arise when this

indispensable commodity i.e. food is misused and mismanaged at any stage of the food life cycle

leading to serious social, economical and environmental consequences.

The leftover or precooked food which generates biodegradable organic waste is termed as food

waste (FW). As per the definition given by The Food and Agriculture Organization (FAO), FW

is “food losses of quality and quantity through the process of the supply chain taking place at

production, post-harvest, and processing stages”. Specifically FW corresponds to the loss of food

at the end of food life cycle (Tsang et al., 2019). Generation of FW also leads to considerable

loss of other resources like water, land, labour and energy. It was estimated by FAO that

annually 1.3 billion tonnes of wasted food is generated globally. This wasted food is one-third of

the total food produced globally, whose production corresponds from 28% of agricultural area

utilizing 1.4 billion hectare of the world’s fertile land (Karthikeyan et al., 2018; Paritosh et al.,

2017). It is projected that economic and population growth will lead to increased FW generation

in next 25 years in Asian countries. The urban FW is expected to rise 138 million tonnes by 2025

as compared to in 2005 (Paritosh et al., 2017). Out of the total waste generated globally, Asia

contributes to highest FW 278 million tonnes, whereas Vietnam produced approximately 11.55

million tonnes of FW (Kiran et al., 2014). This FW includes fresh fruits, vegetables, dairy

products, bakery products, and meat from diverse sources, including discharges from

3
households, hospitality sector, food processing industries, commercial kitchens, and agriculture

waste (Karthikeyan et al., 2018; Kiran et al., 2014).

The disease control centers prevented the use of FW as animal feed, thus preferentially the

disposal of FW was done through fermentation, composting, and landfilling (Tsang et al., 2019).

Conventionally, FW is an element of municipal solid waste which is dumped or incinerated. The

high moisture content of FW leads to the generation of dioxins by incineration, whereas dumping

in open area causes environmental and health issues. FW is estimated to generate 3.3 billion

tonnes of CO2 per year, thereby contributing in the emission of greenhouse gases (Paritosh et al.,

2017). To increase environmental sustainability and overcome socio-economic concerns,

valorization of FW for the production of value added products is an ideal approach attracting

attention of researchers worldwide. This is also evident as the researches on valorization of FW

has increased ≥90% during the last decade from 2009 to 2018 (Fig. 1). Therefore, this review is

to understand the sources and nature of FW that can be efficiently converted to value added

products such as biodiesel, ethanol, bio-hydrogen, methane, butanol, biosurfactants, bio-plastics,

organic fertilizers and electric power generation highlighting the significance of

discarded/dumped FW.

1. Sources of food waste generation

1.1. Food Processing Industries

1.1.1. Cereals and pulses

On a global scale, significant proportion of the human diet is filled by cereal grains obtained

from seeds of Gramineae family such as wheat, rice, barley, maize, sorghum, millet, oat, and rye.

According to the FAO, globally total crop production during 2016 reached 2577.85 million tons.

In contrast, the production of coarse grains (cereal grains other than wheat and rice used

4
primarily for animal feed or brewing) was 1330.02 million tons (FAO-AMIS, 2017). The

production ranking in the year 2014 was corn 1253.6, rice paddy 949.7, wheat 854.9, barley

146.3, oat 23.2, and rye 15.8 tonnes (Papageorgiou and Skendi, 2018). The cereal and pulses

processing industry produce a large quantity of by-products like bran and germ, during

processing (Anal, 2017). India is the worlds’ largest producer of pulses producing a considerable

amount of husk as a by-product during processing (Parate and Talib, 2015). Husk is recycled in

many ways to produce high-end products. There are many crops which generate husk as a by-

product of processing. Apart from utilization as animal feed the straw, husk and dried leaves of

crops like wheat, corn, rice, and barley is utilized in traditional way for making thatching roofs,

baskets, broom, hand fans, handbags and in preparation of decorative items. It is used as cleaning

and polishing agent in metal and machine industries. Rice husk can be used as pet feed fiber,

fertilizer and substrate for vermicomposting technique, and in the production of construction

material like light weight bricks (Kumar et al., 2013). Husk obtained after cocoa pod processing

was utilized for pectin extraction and production of vermicompost, oyster mushrooms, livestock

feed, and other value-added products (Dede et al., 2018). Furthermore, coconut husk has multiple

household applications like rope, broom, mat, tiles, fishing net, and mattresses. It is also

employed for the production of second generation bio-ethanol (Bolivar-Telleria et al., 2018).

These by-products are rich in nutrients, generally consists of dietary fibers, proteins, lipids, fatty

acids, vitamins, minerals and phenolic compounds but still they arrive finally as animal feed,

fuel, and biorefinery substrate. For production of refined flour, bran and germ, a proportion of

grain is removed as they adversely affect the processing properties (Verni et al., 2019). The by-

product of barley pearling process serves as a rich source of bioactive compounds like phytates,

insoluble dietary fiber, phenolics and it contains 2.7 times more vitamin E than in whole barley

5
grain (Papageorgiou and Skendi, 2018). Rice husk is used in fermentation process to adjust

moisture, maintain the porosity of fermentative material for gaseous exchange during distillation

(Tan et al., 2014).

1.1.2. Fruits and vegetables

Fruits and vegetables are energy rich food items with high moisture content having rich nutritive

profile consisting of soluble carbohydrates (glucose, fructose), vitamins, minerals, fibers,

polyphenols and other bioactive compounds (Schieber, 2017). Fruit and vegetable wastes were

generated during different steps of food supply chain starting from farm to fork, including

production, processing, packaging, handling, storage and transportation (Ji et al., 2017). Fruits

and vegetables are classified to waste category only when a consumer disqualifies it from degree

of acceptance. This may arise due to several factors such as discoloration, wounding or chilling,

biochemical reactions (enzymes, antioxidants, phenolic compounds and oxygen), thermal

treatment, microbial attack (rotting, softening and surface growth), and degree of ripening. India

is the second largest producer of vegetables and fruits in the world sharing 10% and 14% of

global production, respectively. It leads to economic loss worth of US $483.9 million per year

due to wastage of about 50 million tons, accounting for 30-40% of total production in India

(Panda et al., 2016). Central de Abasto, the second largest fruit and vegetable market in the

world, at Mexico City, produced 895 tonnes of waste/day. China produces approximately 1.3

million tonnes of this waste per day (Ji et al., 2017). According to a report of FAO in 2014, UK

alone produced 5.5 million tonnes of potatoes; around 3 % to 13 % of harvested crop never

reaches to customer and is wasted due to “grading losses” in supermarkets. This generated waste

is processed by composting, land-filling, incinerating or used as animal feed. These disposal

methods give rise to serious environmental concern such as toxic and greenhouse gas emission,

6
microbial proliferation due to high content of moisture and landfill leachate (Ji et al., 2017;

Dessie et al., 2018).

Reduction of fruits and vegetable waste is warranted to alleviate the increasing demand for food

production and improving the overall efficiency of food supply chain (Matharu et al., 2016).

Growing public concerns about hunger, fruits and vegetable losses, food security reasons,

conserving the environment from pollution, socio-economic factors have accelerated research

into FW domain towards finding better ways of using this natural and renewable resource. The

starch, cellulose and/or hemicelluloses of fruit and vegetable waste is hydrolyzed to soluble

sugars and further fermented to produce ethanol and hydrogen (Diaz et al., 2017). Microbial

processing of fruits and vegetable waste has opened new horizons for value addition to rejected

fruits and vegetables. Several high-end commodities was reported to be produced by utilizing

FW such as fermented beverages (fenny, vineger), single-cell proteins (Saccharomyces sp.,

Candida utilis, Endomycopsis fibuligera and Pichia burtonii), single-cell oils, polysaccharides,

dietary fibre, polyphenols, bio-pigments (carotenoids), fragrances, flavours (vanillin), essential

oils, biopesticides, plant growth regulators, enzymes (cellulase, amylase, protease, phytase, etc),

biohydrogen, bioethanol and biogas (Panda et al., 2016; Schieber 2017; Sabu et al., 2002; Bogar

et al., 2003a; Pandey and Soccol, 2000; Benjamin and Pandey, 1997). Acidogenic fermentation

of fruit and vegetable wastes produces lactic acid (Wu et al., 2015) whereas in solid state

fermentation they are hydrolysed using crude enzyme mixtures to produce succinic acid (Dessie

et al., 2018).

1.1.3. Dairy

Around 29 million tonnes of dairy products are wasted in Europe every year. This dairy waste is

derived from the processing industry, spoilage of the dairy products due to microbial attack, and

7
inappropriate handling (Mahboubi et al., 2017). Dairy waste consists of complex organic

constituents like fat, protein, sugar, traces of food additives, and detergents that are used for

maintaining proper hygiene and clean in place (CIP). Dairy products are the most perishable

commodities due to their rich composition and absorbability. Fungal contamination in milk

produces visible or non-visible defects, such as off-odor and flavor development.

India is reported as the largest milk producing nation and simultaneously produces 1 to 3 times

of effluent for every volume of processed milk, thus generating 3.739 - 11.217 million m3 of

waste per year. While manufacturing of cheese, a considerable amount of whey is produced as a

by-product of processing which generated 9 kg of whey per kg of cheese produced (Parashar et

al., 2016). Another constituent of dairy produce i.e. raw milk, contaminates groundwater due to

the presence of ammonia, nitrogen, and nitrate that is converted to nitrite thereby causing

methemoglobinemia. During processing of raw milk around 2.5- 3.0 litres of wastewater is

generated per litre of processed milk (Singh et al., 2014), carrying about 14–830 mg/l of total

nitrogen concentration (Kushwaha et al., 2011). Wastewater holds significant amount of

nutrients, like carbohydrates, lipids, proteins. Milk proteins dissociates and gives rise to organic

and inorganic forms of nitrogen such as nucleic acids, urea, proteins, and NO− 2, NO− 3, NH+ 4

respectively (Kushwaha et al., 2011). It was found that elevated concentration of NO3 > 40 mg/L

in groundwater is a cause of methemoglobinemia (Fewtrell., 2004).

This raises serious environmental concerns and demands the employment of microbial assisted

method of waste conversion including activated sludge, sequencing batch reactor, tickling filter,

anaerobic sludge blanket, and aerated lagoons (Dias et al., 2014). Dairy waste is rich in organic

matter, facilitating the growth of microorganisms hence a large number of value-added products

can be obtained by utilizing dairy industry waste like lactose and protein (Lapppa et al., 2019). It

8
is a suitable substrate for ethanol production using Saccharomyces cerevisiae via enzymatic

hydrolysis of fermentable sugar (Parashar et al., 2016). Filamentous fungi produce a variety of

enzymes capable of hydrolyzing complex carbohydrates to simple sugar hence aids in high

quality biomass production that can be used as animal / fish feed and even for human

consumption as single cell protein with a GRAS status (Mahboubi et al., 2017).

1.1.4. Edible oil

Edible oil industry generate waste during various steps of refining process like degumming,

neutralization, bleaching, deodorization, oxidative or hydrolytic rancidity. This hydrolytic

rancidity is caused due to the oxidation of lipids, aging, moisture, presence of oxygen and

effluent coming out of industry laden with lots of fatty acids, carbohydrates and protein (Okino-

Delgado et al., 2017). Waste cooking oil is an oil-based substance that resulted from multiple

deep fat frying process which makes fat unsuitable for human consumption due to the formation

of polar compounds like free short-chain fatty acids, mono- and di-glycerides, aldehydes,

ketones, polymers, cyclic and aromatic compounds. It was reported that edible oil industry

annually produces 350.9 million tonnes of de-oiled cake and oil meal as a by-product, which is a

concentrated source of protein. After pretreatment, this waste is further utilized for preparing

human nutrition products, animal feed and fertilizer (Chang et al., 2018).

Traditionally, effluents from oil processing industry were released directly into the soil and

groundwater which leads to oily film formation on aquatic surface causing a serious threat to

survival of aquatic animals, blockage of sewage and drains due to emulsification of organic

matter, oil methanization worsening greenhouse effect (Okino-Delgado et al., 2017). Advance

methods employ microbial cells for biodegradation of organic matter from effluents, thereby

producing various high-end products such as bio-based zwitterionic biosurfactants. Pseudomonas

9
aeruginosa synthesized biosurfactants such as rhamnolipids and glycolipids, biodiesel

production using lipase, liquid hydrocarbon biofuels (Henkel et al., 2012; Chen et al., 2018).

Edible oil industry waste was reported to be a cheap source for health constructive products such

as tocopherols, sterols, squalene, which were used in different industries as raw material, e.g.,

food for SCP production (Diwan et al., 2018), pharmaceutical formulations and cosmetics in the

form of soap stalk (Sherazi et al., 2016).

1.1.5. Meat, poultry and eggs

Meat poultry and egg processing industry is a huge segment of food chain system. European

Union annually accounts for approximately 11 million tonnes of production. About 3.5 billion

pounds of beef was produced by Canada in 2006, contributing $26 billion to its economy.

Consequently, a vast quantity of animal by-products, slaughterhouse waste and wastewater is

generated (Ning et al., 2018). This comprises 49% from cattle, 47% from sheep and lambs, 44%

from pigs and 37% from chicken 37%, which is inedible in nature, thereby generating a huge

mass of waste by slaughterhouses in environment (Adhikari et al., 2018).

Major wastes material generated in industry include feathers, hairs, skin, horn, hooves, soft meat,

deboning residues, bones, etc. In addition to this, the slaughter house wastewater consists of

blood residue, protein, animal fat (lard and tallow), detergent residues and high organic matter

(carbon, nitrogen and phosphorous). Rendering of perishable animal waste extends a possible

alternative way to eradicate the environmental issue along with revenue generation. Rendering

industries produces meat and bone meal, hydrolyzed feather meal, blood meal, fish meal, animal

fats (lard and tallow) (Yaakob et al., 2019). Lactic acid fermentation of slaughterhouse waste is a

promising approach to utilize slaughterhouse waste for the production of lactic acid bacteria that

can be used as a probiotic product (Ashayerizadeh et al., 2017). Due to high nutritional

10
composition slaughterhouse waste can be utilized for various value-added product generation

like biomass (Scenedesmus sp.) as fish feed (Yakoob et al., 2019), a clean energy substitute i.e.

methane produced by anaerobic digestion of wastewater (Ning et al., 2018), biogas production

from poultry litter, blood in food applications (blood sausage, blood cake, blood pudding, blood

curd) and non-food application (fertilizer, binder) (Adhikari et al., 2018). Biodiesel has been

produced from chicken manure biochar by pseudo catalytic transesterification reaction, from

pork fatty waste by fermentation employing Staphylococcus xylosus and from eggshells by

transesterification of triglycerides with methanol using homogeneous catalysts (Marques et al.,

2016). It has multivariate applications in the pharmaceutical, cosmetic product development

industry.

1.1.6. Sea foods and Aquatic life

Marine ecosystem supplies around 20% of the world’s food to humans, therefore plays a vital

role in feeding a significant population of the world. It is estimated that around 183 million

tonnes of seafood would be needed by 2030 for feeding. Generally, 50-70 % of seafood raw

material is wasted every year (Kumar et al., 2018). Globally producing about 6-8 million tonnes

of waste in the form of crabs, shrimp and lobster shells, where Southeast Asia contributes 1.5

million tonnes in totality. In seafood’s the utilizable mass of marine animal is less, crabs yield

40% meat of whole mass, in tuna fishes only 75 % of fillets is available. This generates a huge

amount of waste, including inedible parts like shrimp shells, crab shell, prawn waste, fish scales

and endoskeleton shell of crustacean. Shells and scales of aquatic animals such as shrimps,

lobsters and fishes harbor useful chemicals such as protein, chitin and calcium carbonate. Dried

shrimps and crabs contain about 50% of chitin on dried basis, generating a revenue of around

$100-120 per tonne (Yan and Chen, 2015), and is used as animal feed supplement, bait or

11
fertilizer. Seafood waste is chitinaceous in nature, harbouring pathogenic microbes, carcinogens,

aflatoxins and other health risks it can cause due to bioaccumulation of these contaminants.

The conventional method for seafood waste disposal includes ocean dumping, incineration,

landfilling, and wastewater discharge of seafood processing industry. It contains high organic

material load that potentially causes euthrophication and oxygen depletion of receiving water

bodies (Yan and Chen, 2015). Chitin, the major component of seafood waste is insoluble in

water and inert to most of chemical agents hence leads to environmental pollution and bio-

fouling, thus stipulating biological processing of this waste material as a step toward

environment protection and a sustainable way of billion-dollar revenue generation as bio-

economy (Yan and Chen, 2015; Kumar et al., 2018).

Indian shrimp processing industries produces more than 0.15 million tonnes of shrimp waste

annually. Waste of shrimp processing industries was used to produce nutraceutical compound

such as astaxanthin (3, 3’-dihydroxy-ß-carotene-4, 4’-Dione), a xanthophyll carotenoid present

in crustacean waste that was extracted through oxidative transformations of ingested β-carotene

or zeaxanthin by feed microalgae (Prameela et al., 2017). Chitosan is an important biopolymer

extracted from exoskeletons of crustaceans waste. It was reported to exhibit antibacterial activity

against Enterococcus faecalis, Escherichia coli, Staphylococcus aureus, and Candida albicans

(Hussein et al., 2012). Glycosaminoglycans (GAGs) extracted from marine animal waste is of

better quality to that of terrestrial organisms (Valcarcel et al., 2017). Waste of Seafood

processing industries is a potential source for functional and bioactive compounds produced

through enzyme-mediated hydrolysis.

1.2. Commercial and households Kitchens

12
Urbanization, rapid economic development and uncontrolled population growth has increased

the consumption of food leading to many folds increase in the generation of kitchen waste

annually (Zhao et al., 2017). In 2011, rural areas of China produced 200,000 kg of domestic

waste. Presently China is producing more than 30 million tonnes of kitchen waste every year. It

has been estimated that annually 2.5 billion tonnes of FW is produced by European Union out of

food supply chain (Li et al., 2017).

Kitchen waste (KW) is a kind of anthropogenic organic waste, usually discharged from public

catering rooms, restaurants, households, canteens of school and factory etc. (Li et al., 2017; Zhao

et al., 2017; Liu et al., 2019). The waste generated by restaurants, commercial and institutional

kitchens is different from municipal solid waste and is referred to as kitchen waste (KW). KW

includes fruits, vegetables, cooked food wastes, meat, used fat, oil and grease. On wet basis KW

broadly comprises of fruits 38.2%, vegetables 41.5%, staple food 7.6%, egg shell bones 7.2%,

shells and pits 2.5%, and meat 2.3% (Zhao et al., 2017). Chemically it comprises of carbohydrate

polymers (cellulose, hemicellulose, pectin and starch), protein, lignin, fats, organic acids,

inorganic salts and others (Chen et al., 2017; Zhao et al., 2017). KW is generated during various

food processing operations such as handling, processing, production, storage, transportation and

consumption. Commercial and household Kitchen wastewater is generated during various

activities like washing and rinsing foodstuffs, cooking, cleaning dishes, cooking utensils, and

general housekeeping.

Traditional methods of decomposition of kitchen waste such as land-filling, composting,

incineration and direct or indirect discharge of wastewater into the environmental system is

detrimental to the ecosystem and human health (Chen et al., 2019). Kitchen waste is

biodegradable biomass with higher moisture content and a pool of nutrients facilitating the

13
growth of pathogenic microorganisms causing rotting and breeding of flies and mosquitoes in

shorter span of time. It emits toxic substances, greenhouse gases, a huge amount of leachate in

water bodies and foul smell of ammonia and hydrothion. Ammonia produced during

decomposition of kitchen waste has strong, pungent order which can cause serious irritation in

the respiratory tract, redness of eyes and skin, while hydrothion is highly toxic to humans (Zhao

et al., 2017). The uncontrolled generation and improper management could produce lethal and

life-threatening consequences on the environment. It was reported that kitchen waste could be

used as a substrate for generation of numerous high value products viz. biosurfactant production

using Pseudomonas aeruginosa (Chen et al., 2018), butanol production by enzymatic hydrolysis

(Chen et al., 2017), lactic acid production by Lactobacillus amylophilus, volatile fatty acids and

hydrogen from mixed culture (Liu et al., 2019), cellulose production via Aspergillus niger in

solid state fermentation, ethanol production by a process of successive liquefaction, pre-

saccharification, and simultaneous saccharification and fermentation (Nishimura et al., 2017). It

can be used to harness energy liberating products like biogas, bioelectricity, biodiesel, etc.

Nano-composites, biopolymers and edible film like materials can be synthesized using FW as

substrate. FW can be transformed to huge array of value-added products including antioxidants,

pigment, nutraceuticals, dietary fiber, organic acids, high fructose syrup, single-cell protein,

vermicompost, biofertilizer, xanthan gum, and wax esters, simultaneously reducing

environmental burden (Liu et al., 2019).

1.3. Agricultural Waste

Waste framework directive 2008/98/EC laws defines waste as “any substance or object which

the holder discards or intends or is required to discard”. Agriculture waste is an organic

substance involving straw, bagasse, molasses, spent grains, husk (rice, maize, and wheat), shell

14
(walnut, coconut, and groundnut), skin (banana, avocado), crop stalks (cotton), plant waste,

livestock and poultry manure (Dai et al., 2018). In 2013, FAO reported that about 250 million

tonnes of non-edible plant waste from different crop processing is generated as agro-industrial

waste (Heredia-Guerrero et al., 2017). Being world’s largest grain producer, China produced

1.75×109 tons of agriculture waste, of which 9.93×108 tonnes was contributed by crop straw,

4.52×108 tonnes from livestock and poultry manure, and 3.03×108 tonnes from forest residues in

2013 (Dai et al., 2018). Asia alone generates 4.4 billion tonnes of solid wastes annually. Agro-

industrial waste generation from different sources in India is more than 350 million tonnes per

year (Madurwar et al., 2013).

Traditionally, agricultural waste is either incinerated/burnt off or allowed to rot in fields, thereby

causing serious air pollution and is also exacerbating soil pollution, water pollution and food

contamination. These traditional approaches liberate toxic gases (such as N2O, SO2, CH4,),

smoke, greenhouse gases into thfe air, and other carcinogenic chemicals such as dioxins, furans

and polycyclic aromatic hydrocarbons, which are detrimental to the environment as well as for

human health. Exposure to these chemicals causes severe development damage in fetuses,

infants, children, and adults (Cheng and Hu, 2010). Agricultural waste is biodegradable and

organic, possessing a repository of nutrients such as polysaccharides (starches, cellulose,

hemicellulose), proteins, lignins, fibers, minerals, vitamins, and others (Madurwar et al., 2013).

Agriculture waste is porous and loose in constitution containing carboxyl, hydroxyl, and other

reactive groups, so agricultural biomass can be used for wastewater remediation as an adsorption

material, hence “reducing waste by waste” (Dai et al., 2018). Apart this, the chemical

composition of agriculture waste proves it as a versatile candidate bearing potential to synthesize

15
a number of products such as bioplastic from cuticles present on the outer layer of plants parts

such as leaves, stem, flowers (Heredia-Guerrero et al., 2017).

Agriculture waste can be a cheap and natural substitute for production of multiple high valued

products. Microbes can readily feed upon agriculture waste to generate an array of high end

products such as pigments, phytochemicals, antibiotics, different enzymes (endoglucanase, β-

glucosidase, amylase, glucoamylase) by utilizing peels, seeds, oil cakes, field residues, and bran

(Bogar et al., 2003b; Selvakumar et al., 1998; Singh et al., 2006). Xanthan is a type of

exopolysaccharide that acts as food additive in food industry and is reported to be produced by

action of Xanthomonas species on agro waste as substrate (Sadh et al., 2018).

Food additives play a significant role in enhancing the technological properties of food.

Mushroom is ecology and economy balancing crop derived of lignocellulosic agro waste (wheat

paddy, rice paddy, banana leaves, cotton stalks) by mushroom fungi Lentinula edodes and

Pleurotus sp. (Philippoussis, 2009). Agro-industrial waste is reported to be a good carrier for

enzyme immobilization and solid state fermentation (Sadh et al., 2018).

Agricultural material can be utilized to produce suitable substitutes of construction material with

improved qualities like light weight, biodegradable and eco-friendly material. It can be used to

develop several construction items like fiber-board made from cotton stalk with no chemical

additives, thermal insulating walls and roofs, waste-create bricks made from recycled paper mills

waste and cotton waste. Cement replacer is manufactured from sugar industries waste (bagasse

ash) and oil palm shell as a coarse aggregate for structural concrete production (Madurwar et al.,

2013).

2. Food waste utilization for energy production

16
The current strategies of landfilling or incinerating FW do not eliminate the environmental and

economic stress thus valorization is gaining much interest. FW can be converted to different

forms of energy molecules or biofuels, viz. biogas, hydrogen, ethanol and biodiesel, butanol and

methane (Table. 2).

2.1. Production of biofuels

2.1.1. Biodiesel

Increasing environmental pollution, fuel demand, and depletion of fossil fuels have intensified

the requirement of alternative fuels. Biodiesel emerges as an alternative fuel that can be acquired

from oils and fats. It is a green fuel whose production is expensive because of the high cost of

feedstock, thus in order to reduce the cost, possibility to utilize FW as lost cost feedstock have

been investigated (Karmee et al., 2015). FW can be converted to biodiesel by direct

transesterification employing acid/alkaline catalyst or of microbial oils that are produced by

oleaginous microorganisms (Kiran et al., 2014). Microbial oils have similar fatty acid

composition as plant oil thus microbial oils can be used as raw material for production of

biodiesel. FW hydrolyzate can be used as nutrient source and culture medium for the cultivation

of microalgae for biodiesel production. Aspergillus oryzae and Aspergillus awamori was used to

prepare FW hydrolyzate, which served as growth medium for cultivation of Chlorella

pyrenoidosa and Schizochytrium mangrovei yielding 10-20 g biomass. The fatty acids produced

by C. pyrenoidosa and S. mangrovei were suitable for the production of biodiesel (Pleissner et

al., 2013). Waste cooking olive oil was reported to serve as a substrate by Penicillium expansum

and five different strains of Aspergillus sp. for the production of biomass rich in lipid. Among

these, Aspergillus sp. ATHUM 3482 yielded highest amount of lipid 0.64 g/g dry cell weight

(Papanikolaou et al., 2011). Biodiesel production from vegetable oils, animal fats and butter was

17
reported to globally yield 24.5 GJ energy per year (Kiran et al., 2014). Cubas et al., (2016)

reported biodiesel production employing corona discharge plasma reactor technology (CDPT).

This technique offers several advantages such as increased esterification, easy biodiesel

separation, and no co-product generation. CDPT has been efficiently used for biodiesel

production from waste frying oil in the absence of chemical catalyst.

2.1.2. Ethanol

Wide industrial application of ethanol has increased its demand globally. It is prominently used

as a feedstock chemical for synthesis of ethylene (Kiran et al., 2014) and an essential raw

material for production of polyethylene. Traditionally cellulose and starchy crops, e.g. sugar

cane, rice, and potato were used for production of bio based ethanol (Thomsen et al., 2003).

Commercial enzymes are available to convert starch to glucose which is further fermented to

ethanol by Saccharomyces cerevisiae, whereas cellulose hydrolysis is difficult (Kiran et al.,

2014). Thus FW with low cellulosic content serves as a better alternative for the production of

bioethanol. To improve the purity and yield of ethanol, FW is autoclaved prior to fermentation,

as harsh or thermal treatment may cause partial degradation of nutritional components and sugars

(Sakai and Ezaki 2006). Dried FW has reduced surface area which results in decreased reaction

efficiency between substrate and enzyme, thus fresh and wet FW was reported to be an efficient

source for ethanol production. Furthermore as cellulose or starch cannot be directly converted to

ethanol by yeast thus the conversion efficiency is dependent on carbohydrate saccharification

(Kiran et al., 2014). For this a mixture of enzymes namely glucoamylase, α-amylase, β-amylase

and pullulanase etc. will be added for high molecular weight substrates. Hong and Yoon, (2011)

reported the production of 36 g ethanol and 60 g reducing sugar in 48 h of fermentation by

utilizing 100 g of FW. Kitchen garbage and non-diluted FW was reported to yield 17.7 g/L/h and

18
0.49 g ethanol per g sugar by simultaneous saccharification and fermentation process (Ma et al.,

2009). Several countries including Japan, Finland and Spain had developed pilot scale plants to

convert their FW to bioethanol (Kiran et al., 2014).

2.1.3. Biohydrogen

Hydrogen is a potential renewable energy source with high energy yield of 142 MJ/kg

(Jarunglumlert et al., 2018). In nature, hydrogen is not readily available but can be produced

from primary energy source. Hydrogen being carbon free with the highest energy output and

yielding water on combustion is globally used as a substitute to fossil fuels (Nikolaidis and

Poullikkas, 2017). Biohydrogen is hydrogen gas produced employing biological processes. The

production of biohydrogen through fermentation using FW requires less energy and

simultaneously recycles the waste generated, thus it has become the most favored method.

Carbohydrate-rich FW is preferred for the production of biohydrogen gas as it has 20 time higher

potential than protein or fat-based FW. Hydrogen production from FW had been reported

employing several fermentation processes such as continuous, semi-continuous, batch, single or

multiple stages (Kiran et al., 2014). Upflow anaerobic sludge blanket (UASB) and anaerobic

sequencing batch (ASBR) reactors have been used with high hydrogen producing rates because

of their high biomass concentration in the reactor (Karthikeyan et al., 2018). For these processes,

solid retention time (SRT), hydraulic retention time (HRT), and organic loading rate (OLR)

affect the production of hydrogen. An optimized SRT with low HRT enhanced the technical

feasibility and productivity of biohydrogen production. However, the role of a higher OLR is yet

debatable as it affects the process in both ways, suggesting an optimal OLR for maximum

biohydrogen production (Kiran et al., 2014).

19
As in anaerobic digestion, the process of dark fermentation is set at low HRT with high acidic

condition to inhibit methanogenic activity. The dark fermentation process for the production of

biohydrogen from glucose follows two major pathways, viz. butyrate and acetate pathways that

utilize one mole of glucose, yielding two and four moles of biohydrogen, respectively

(Karthikeyan et al., 2018). Mixed cultures of Enterobacter and Clostridium produce hydrogen

from waste, which is readily utilized by hydrogenotrophic bacteria (Li and Fang 2007). Seed

biomass is heated to reduce microbial biohydrogen consumers, while suppressing lactate

production, thus increasing biohydrogen production. Untreated FW abundantly contain lactic

acid bacteria whereas pretreated FW is dominated by biohydrogen producers (Kiran et al., 2014).

2.1.4. Methane

Anaerobic production of methane is favored because of its renewable energy source utilization,

low residual waste production and low cost. The waste produced through this process is nutrient

rich that can be used as soil conditioner or fertilizer (Kiran et al., 2014). The energy content of

methane is 55.5 MJ/kg. Anaerobic digestion produces methane through biodegrading and

reducing organic waste. The production of methane by this process is affected by several

parameters such as alkalinity, pH, organic loading rate, nutrients, reactor type, volatile fatty

acids, carbon/nitrogen ratio, operation temperatures, ammonium ions, and substrate

characteristics (Park et al., 2018). A decrease in pH and volatile fatty acids accumulation

minimizes the production of methane gas during anaerobic digestion (Chen et al., 2008). Park et

al., (2018) reported that the use of microbial electrolysis cell (MEC) with anaerobic digestion

reactor enhances the methane production rate by 1.7 times as compared to the anaerobic

digestion reactor alone. MEC increases the rate of degradation of volatile fatty acids,

concentrated organic wastes and non-degradable organic matter thereby improving methane

20
production. During this process, methane is formed at cathode by electrons released from

exoelectrogenic bacteria when MEC passes a low voltage in the reactor.

Pretreatment of FW could be an efficient strategy that aids in proteins/lipids digestibility,

reducing acidification rate, altering biological and physico-chemical properties, thus avoiding

process inhibition and improving the recovery of methane. The pretreatment process commonly

includes physical (grinding), thermal, acid and alkali treatment, high-pressure treatment, pulse

discharge of high voltage, microwave mediated, micro-aeration and biological treatment

(Karthikeyan et al., 2018). Thermal treatment followed by alkali treatment is the best

pretreatment strategies for anaerobic digestion of FW. Alkali pretreatment enhanced the yield of

methane by 25%, whereas when combined with thermal treatment, the yield further enhanced to

32% (Naran et al., 2016). FW of 54 different fruits and vegetables produced 180–732 mL

methane per g volatile solid. Furthermore fruits and vegetables waste in a two stage anaerobic

digester yielded 530 mL per g volatile solid by utilizing 95.1% volatile solids (Kiran et al.,

2014). Zhao et al., (2017) reported the effect of presence of varying salt (NaCl) concentrations in

FW. They observed that low salt concentration increased the acidification and hydrolysis

processes while inhibiting methanogenesis whereas high concentrations inhibited both

methanogenesis and acidification.

2.1.5. Biobutanol

Butanol, a four carbon alcohol is considered more advanced biofuel compared to ethanol as it

offers several advantages such as improved combustion efficiency, higher energy density, lower

vapour pressure and property to dissolve in vegetable oils in order to reduce their viscosity

(Girotto et al., 2015). Traditionally, cane molasses and starch (corn, potato, and wheat) are used

for the production of biobutanol through fermentation process. Economic viability of biobutanol

21
production via fermentation process is mainly influenced by the substrate cost, which accounts

for about 50% of the cost of production (Ujor et al., 2014). Several studies have reported the

efficiency of Clostridium species for the production of biobutanol using FW as a substrate

(Girotto et al., 2015; Huang et al., 2015; Ujor et al., 2014). Clostridium acetobutylicum produced

biobutanol through fermentation process by utilizing FW. Lactose-rich waste whey yielded 0.3 g

of butanol per g of carbohydrates (Girotto et al., 2015). Similar yields of biobutanol were

observed from starch-rich industrial FW such as bread liquid, batter liquid and inedible dough

(Ujor et al., 2014). Clostridium beijerinckii strain P260 utilized 81 g/L of FW procured from

retail store in Illinois, USA containing white bread, sweet corn, and mashed potatoes to produce

biobutanol with a yield of 0.38 g/g and a high productivity of 0.46 g/L/h (Huang et al., 2015).

Jesse et al., (2002) reported varying production of acetone:butanol:ethanol (ABE) by Clostridium

beijerinckii strain BA101 upon action on different FW types, viz. agricultural waste yields 20.3

g/L and starch-rich packing peanuts 21.7 g/L whereas control starch yielded 24.7 g/L ABE. This

difference in production could be attributed to the difference in the nature of the waste material.

Since employing FW showed reasonably good quantities of biobutanol, FW valorization for

biobutanol production can be an efficient strategy for waste management, promoting economic

viability.

2.2. Electric power generation

Since most of the FW generated was disposed through conventional methods like incineration,

compost, and landfill, which were uneconomical and unsustainable processes, leading to toxic

gas emission or ground water contamination (Paritosh et al., 2017). Thus, recovering energy or

electricity employing FW is considered as eco-friendly, economic, pollution reducing and

sustainable approach. This can be achieved by anaerobically treating the FW in specific devices

22
such as microbial fuel cell (MFC) (Li et al., 2016). MFC utilizes microorganisms as catalyst for

recovery of electricity generated by using diverse wastes including industrial wastewater

domestic wastewater and excess sludge (Li et al., 2016; Cercado-Quezada et al., 2010). Briefly

in MFC, microorganisms oxidize organic matter transferring electrons to anode and at cathode

the oxidized compounds or oxygen get reduced microbially or by abiotic process (Cercado-

Quezada et al., 2010). Organic matter rich FW serves as energy source for electricigens in MFC,

hydrolysis of this organic fraction is the rate limiting step in electricity production (Li et al.,

2016). Pretreatment of FW employing microwave and sonication was reported to further enhance

substrate hydrolysis, which in turn increases the efficiency of electricity generation (Yusoff et

al., 2013). MFC containing FW leachate at a concentration of 5000 mg/L produced maximum

power 15.14 W/m3 and open circuit voltage of 1.12 V. Power output reduced with increasing

substrate concentration 20,000 mg/L; this reduction was attributed to anode chamber microbial

inhibition (Rikame et al., 2012). MFC performance was significantly decreased by the deposition

of cations and microorganisms on fouled membranes. Jia et al., (2013) reported the microbial

community structure in MFC loaded with FW collected from canteen of Harbin Institute of

Technology. They have reported a maximum 18 W/m3 power density at a chemical oxygen

demand (COD) of 3200 ± 400 mg/L. The 454 pyrosequencing of the amplified 16S rRNA gene

revealed the presence of different genera in anode biofilm of which fermentative Bacteroide and

exoelectrogenic Geobacter were the dominant ones. Food industry wastes such as wine lees,

yogurt waste and fermented apple juice in combination with two inoculums sources garden

compost and anaerobic sludge was evaluated for electricity production by MFC (Cercado-

Quezada et al., 2010). Of these, only yogurt waste inoculated with compost leachate exhibited

the generation of stable power density of 44 mW/m2. Organic fraction rich composite FW from

23
canteen of CSIR- Indian Institute of Chemical Technology (IICT), India generated electricity

upon action of anaerobic consortia as anodic biocatalyst in MFC. It was shown that OLR

significantly affected the production of electricity from FW. OLR at 1.01, 1.74, and 2.61 kg

COD/m3-day generated 188, 295, and 250 mV electricity, respectively (Goud et al., 2011).

3. Bio-conversion of food waste to value added products

3.1. Biosurfactants

Biosurfactants are surface active compounds of biological origin prominently produced by

diverse microorganisms including bacteria, fungi, and yeast (Gaur et al., 2019a; Gaur et al.,

2019b). Globally, they are estimated to generate a revenue of over 18 Billion USD with a market

of 30.64 Billion USD in 2016 (Singh et al., 2019). The compound annual growth rate of

biosurfactant market is estimated to be 5.6 % from 2017 to 2022. This increasing demand

impulse to explore cheap waste material as substrates thus reducing the production cost while

obligating waste management. Thus, FW from house-holds and various food industries can be

employed as substrate for biosurfactant production aiding in curtailing the production cost while

diminishing the pollution. One of the prominent FW produced from house-holds and commercial

kitchens is used waste oil. Kitchen waste oil (KWO) is rich in protein and moisture content, thus

encourages microbial growth. Pseudomonas aeruginosa isolated from KWO preferentially

utilized KWO over glucose, glycerol, molasses, and rapeseed oil as a fermentation substrate for

biosurfactant production (Chen et al., 2018). Another major waste from Indian food (dairy)

industry is from paneer production. With the annual production of 0.15 million tonnes of paneer

generated two million tonnes of waste whey, which is often released in the environment without

any pretreatment that leads to soil and water pollution (Parashar et al., 2016; Patowary et al.,

2016). Pseudomonas aeruginosa SR17, a hydrocarbon-contaminated soil isolate utilized paneer

24
whey to yield 2.7 g/L of biosurfactant (Table. 2). The production further enhanced to 4.8 g/L by

additionally supplementing it with mineral salts and glucose (Patowary et al., 2016). Another

strain of Pseudomonas aeruginosa ATCC 10145 utilized soy molasses as sole carbon source for

biosurfactant production (Rodrigues et al., 2017). A strain of Pseudozyma sp. produced

biosurfactant which showed potential application as laundry detergent additives (Sajna et al.,

2013). Soy molasses is generated during soyabean processing having low commercial value,

although rich in proteins, carbohydrates, and lipids. Pseudomonas aeruginosa ATCC 10145

produce 11.7 g/L glycolipid biosurfactant by utilizing 120 g soy molasses as fermentation

substrate. Ramírez et al., (2015) reported that Bacillus subtilis and Pseudomonas aeruginosa

utilized olive oil mill waste (OW) to synthesize biosurfactant. These bacteria utilize remaining

oil in OW supplements as carbon source, whereas other waste components serve as nutrients.

3.2. Bio-plastics

Plastics are traditionally being synthesized from petrochemicals through irreversible processes

(Tsang et al., 2019). Petroleum derived polymers are difficult to degrade by microorganisms and

their high persistence poses serious environmental concerns thus an alternative to these synthetic

plastics, i.e., bioplastics comes into play. As microorganisms utilizing various waste products

can synthesize these bioplastics. These bioplastics are preferred over synthetic ones delineating

environmental burden while being ecofriendly. Substitution with bioplastics also offers a

reduction in global warming concern as the energy requirement for petroleum based synthetic

plastic production (77 MJ/kg) is more as compared to bioplastics (57 MJ/kg) (Gironi and

Piemonte, 2011). Land-filling of FW leads to undesirable outcomes such as groundwater

contamination and greenhouse gas emissions, thus bioconversion of FW to generate bioplastics

is an optimal strategy for waste disposal. The bioconversion of FW to plastics requires

25
pretreatment to enhance biological and physico-chemical properties. The pretreatment strategies

include physical, chemical, biological and enzymatic hydrolysis. Physical treatment converts FW

into fermentable organic compounds employing thermal and mechanical processes, including

heating, milling, ultrasound, and microwaves (Tsang et al., 2019). Fermentable sugars are

formed using chemical treatment, which includes acid or alkali treatment. Biological treatment

includes microorganism to utilize FW as fermentable substrate. Polyhydroxyalkanoate (PHA),

hydroxybutyrate (PHB), polybutylene succinate (PBS), starch blends, polyvinyl alcohol (PVA)

and polylactic acid (PLA) are the major biodegradable polymers (Prabisha et al., 2015; Pandey

and Soccol, 1998; John et al., 2007; Ramachandran et al., 2007; Tripathi et al., 2019; Tsang et

al., 2019).

Alcaligenes sp. NCIM 5085 through an optimized fermentation process (7.5 L) utilized cane

molasses and yielded 70.89 % of high molecular weight PHB with 0.312 g/L/h productivity

(Tripathi et al., 2019). Another strain Halomonas campaniensis strain LS21 grew in cellulose,

starch, fatty acids, fats, and proteins rich FW and produced 70% PHB at 37 °C. Bacillus

megaterium SRKP-3 utilized dairy waste to produce PHB (Pandian et al., 2010, Tsang et al.,

2019). Felix et al., (2015) reported the production of bioplastics from freshwater red swamp

crayfish. As per the United States Department of Agriculture, 45 % of the Crayfish entering in

United States of America food market resulted in waste only. Guidelines by European Union

suggested the preferential use of FW as animal feed, but disease control concerns made it illegal.

Thus, valorizing FW by converting it to value-added products holds an ideal end use practice.

3.3. Organic fertilizers

Conventional inorganic fertilizers contribute to increased atmospheric methane emission; organic

fertilizers are considered effective alternative improving yield of crops along with reduction in

26
methane emission. As per a market research, it has been estimated that emerging market of

organic fertilizer would touch a value of over $150-109 per annum by 2020. FW has been

traditionally used as animal feed and organic fertilizer prepared by composting or

vermicomposting (Du et al., 2018). Agriculture waste has been utilized for mushroom

cultivation as a substrate (Philippoussis et al., 2006). It reduces environmental burden and also at

the same time enhances crop productivity and changes soil bacterial community. Residue of

biogas production from FW can be used as organic fertilizers or soil conditioner due to

nutritional and carbon content along with macronutrients (N, K, P, Ca, Mg) and microelements

(Fe, Cu, Zn and Al) capable of improving and stimulating plant growth (Zhu et al., 2015).

Organic fertilizers can be synthesized from FW by employing several processes such as

anaerobic digestion, aerobic composting using microbes, chemical hydrolysis method (treating

FW via alkaline or acid hydrolysis at 600-1000 C), and in-situ degradation of natural organic

matter. It produces fertilizers in the form of digestate / soil conditioner, compost, soluble bio-

waste compost (SBC), degraded crop, minerals and as liquid organic fertilizers (Du et al., 2018).

Liquid organic fertilizers (LOF) are directly delivered at root zone of individual plant in

irrigation system and are therefore, advantageous in plant growth than other fertilizers. They are

readily available for absorption by plant and the quantity required per field is also less, as well as

the degradation process of LOF is quite easier (More et al., 2017). The efficacy of organic

fertilizers can further be improved by combining methane oxidizing bacteria such as

methanotrophs (Singh and Strong 2016). Organic fertilizers can support the growth of

microalgae also. It can be used as an alternative nutrient medium to cultivate Chlorella vulgaris

for synthesis of biodiesel (Lam and Lee, 2012).

4. Conclusion

27
Food is an indispensable commodity contributing to major section of organic waste generated

worldwide. Improper management of FW leads to environmental hazards by releasing toxic

components viz. greenhouse gases, nitrates, ammonia etc.. Presently, microbial processing of

FW offers environmental protection and a sustainable way for the genesis of billion dollar

revenue. It can be concluded from this review that microorganisms can be efficiently employed

for biotransforming FW into complex biomolecules, bio-fertilizers, biofuels, biochemicals and

electrical energy. As FW is a rich source of nutrients, its valorization is proven to be a promising

approach towards FW management.

Acknowledgment

The authors do not received any financial support for publication of this article.

28
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Legends

Table. 1. Value added and bioactive compounds from different food processing industrial waste.

Table. 2. Biological process for valorization of food waste.

Food Waste Types of Value added and bioactive Reference

Industry generation food compounds
category (Kilo processed
tonnes)
Fruits NA Grape Ethanol, dietary fibre, Galanakis 2017;
Processing processing grape seed oil, pomace oil, Schieber 2017
Industry Industry oleanolic acid, polyphenols
(catechin, epicatechin, gallic
acid, and resveratrol), flavanols
(proanthocyanidins),
anthocyanins (enocyanin),
procyanidins, tartates, malates,
citric acid, single cell protein.
5742 Apple Pectin, lactic acid, citric acid, Schieber 2017; Kiran
juice aroma compounds, biogas, et al., 2014
processing ethanol, butanol, and
industry pectinases
NA Citrus Essential oil (limonene), Matharu et al. 2016
processing phenolics, pectin, antioxidants,
industry ethanol, organic acids, and
flavanoids
NA Mango Starch, fiber, sterols, Schieber 2017
tocopherols, tannins, flavonols,
xanthones, anthocyanins, and
alkylresorcinols

44
 13532 Banana Lignin, pectin, cellulose, Schieber 2017;
hemicellulose, phenolic Kiran et al., 2014
compounds (prodelphinidins,
flavonol glycosides),
procyanidins, and flavanols

1829 Pineapple Pectin, phenolic compounds, Schieber 2017; Kiran

carotenoids and bromelain, and et al., 2014
dietary fibre
NA Berries Phytochemicals, polyphenols, Rohm et al., 2015
pectin and dietary fibre
Vegetable 62229 Potatoes Lysine, protein (patatin), Kiran et al., 2014;
processing Steroidal alkaloids, cellulolytic Matharu et al. 2016;
industry enzymes, adsorption dyes, and Schieber 2017
biopolymer films
12874 Tomatoes Carotenoids (lycopene) and Kiran et al., 2014;
pectin Schieber 2017
Carrot α-carotene, β-carotene Schieber 2017
and dietry fibre
5891 Onions Pectin, fructans, phenolic Kiran et al., 2014;
compounds and dietary fiber Schieber 2017
Cereal and NA Wheat Carbohydrates, Schieber 2017
Pulses oligosaccharides, phenolic
industry compounds, lipid soluble
vitamins, folic acid,
phytosterols, amino acids and
peptides
26738 Rice bran Proteins, lipids, dietary fiber, Kiran et al., 2014;
minerals, Schieber 2017
and antioxidants (vitamin E
and oryzanol)
2735 Legumes Activated carbon, proteins, Kiran et al., 2014;
lipids, fatty acids, vitamins, Parate and Talib,
minerals and phenolic 2015
compounds
Beverage 105 Coffee Antioxidants, vitamins, Murthy and Naidu,
Industry enzymes, cellulose, starch, 2012; Kiran et al.,
lipids, proteins, pigments, citric 2014
acid, gibberellic acid, ethanol,
biogas, dyes, and dietary fibres

45
 (cellulose, hemicelluloses,
lignin, pectin, gums)
NA Tea Caffeine, polyphenols, Sui et al., 2019
triacontanol, and saponins
Dairy 16560 Milk Biodiesel, ethanol, whey Kiran et al., 2014;
Industry protein, Lactose, baker’s yeast, Parashar et al., 2016;
and minerals Lapppa et al., 2019
Meat and 1344.5 Meat and Fertilizer, animal feed, blood Kiran et al., 2014;
Seafood poultry meal, meat and bone meal, Ning et al., 2018;
Processing feather meal, lactic acid, and Yaakob et al., 2019
Industry probiotics,
NA Fishes Chitosan, and Prameela et al., 2017
glycosaminoglycans,
6000 to Shrimps Nutraceuticals (Astaxanthin), Kiran et al., 2014,
8000 chitin and chitinase Yan and chen, 2015;
Prameela et al., 2017;
Kumar et al., 2018
Crabs Chitin, calcium carbonate and Yan and chen, 2015
protein
Lobster Chitin Yan and chen, 2015
Edible oil 21462 Oil Biosurfactants Henkel et al., 2012,
Industry like rhamnolipids and Kiran et al., 2014
glycolipids, biodiesel,
tocopherols, sterols, squalene,
and single cell protein
Olives Phenolic compounds, Kiran et al., 2014;
polyphenols, carotenoids, Schieber 2017
phytosterols, squalene, and
dietary fiber

46
S. No. Substrate Biological Process Microbes Product References
Associated Associated Obtained
1. Noodle Waste Saccharification Saccharomyces Bioethanol and Yang et al.,
and fermentation cerevisiae K35 Biodiesel 2014
2. Waste cooking Fermentation Penicillium Biodiesel Papanikolaou
olive oil expansum et al., 2011
3. Mixed Food Enzymatic A mixture of α- Bioethanol Karmee et
Waste (Potato Hydrolysis and amylase, al., 2016
peel waste, Fermentation βamylase, and
Banana Peel, glucoamylase;
Household Saccharomyces
waste) cerevisiae H058
4. Agricultural Enzymatic Carbohydrase, Hydrochars and Karmee et
residue waste hydrolysis and protease and bio-oil al., 2016
Flash Pyrolysis lipase
5. Cooking oil Enzyme Lipase Biodiesel Heater et al.,
waste immobilization 2019
6. Spent coffee Extraction and Catalyst (KOH) Biodiesel Kondamudi
grounds transesterification et al., 2008
7. Cane molasses Fermentation Clostridium Biobutanol Girotto et al.,
and starch rich acetobutylicum, 2015; Huang
food waste Clostridium et al., 2015;
beijerinckii Ujor et al.,
P260 2014
8. Mixed food Microbial Exoelectrogenic Methane Park et al.,
Waste electrolysis cell bacteria 2018
(MEC) and
Anaerobic
Digestion
10. Carbohydrate Fermentation, Up-flow Biohydrogen Kiran et al.,
rich food waste anaerobic sludge 2014,
blanket (UASB) Karthikeyan
and anaerobic et al., 2018
sequencing
batch (ASBR)
reactors
11. Industrial Microbial Fuel Cell Catalyst Electricity Li et al.,
wastewater (Microbial cells) 2016;

47
 domestic Cercado-
wastewater Quezada et
and excess al., 2010
sludge
12. Kitchen waste Fermentation Pseudomonas Biosurfactant Chen et al.,
oil aeruginosa 2018
13. Soy molasses Fermentation Pseudomonas Glycolipid Rodrigues et
aeruginosa biosurfactant al., 2017
ATCC 10145
14. Dairy effluent Fermentation Pseudomonas Biosurfactant Patowary et
(cheese whey) aeruginosa al., 2016
SR17
15. olive oil mill Fermentation Bacillus subtilis Biosurfactant Ramírez et
waste and al., (2015
Pseudomonas
aeruginosa
16. Cane molasses Fermentation and Alcaligenes sp. Polyhydroxybutyr Tripathi et
biosynthesis NCIM 5085 ate (PHB) al., 2019
17. Nutrient-rich Hydrolysis, Halomonashydr Polyhydroxybutyr Tsang et al.,
food waste fermentation and othermalis, ate (PHB) 2019
Biosynthesis Halomonascamp
aniensis
18. Dairy waste Fermentation and Bacillus Polyhydroxybutyr Pandian et al.
biosynthesis megaterium ate (PHB) 2010, Tsang
SRKP-3 et al., 2019
19. Food waste Anaerobic Microbial cells Liquid organic Ma et al.,
digestion, aerobic fertilizer and solid 2019, More
composting fertilizers et al., 2017

48
49
Highlights

Biofuel and bio-electricity production using food waste reduces environmental burden.

50