Trends in Food Science & Technology 21 (2010) 77e84

Review

Brewer’s
Saccharomyces yeast has an ancient tradition and is still a dynamic sector open
to new developments in technology and scientific progress.
Nowadays, beer is one of the most popular alcoholic bever-
biomass: ages, thus, brewing industry is a huge global business.
Brewer’s are very concerned that the techniques they use

characteristics and are the best in terms of product quality and cost
effectiveness.
Brewer’s produce beer at an advanced technological
potential applications level while keeping in mind the importance of tradition.
A great many of different types, or style, of beer are brewed
across the world. During production, beer alternately goes
I.M.P.L.V.O. Ferreiraa,*, through chemical and biochemical reactions (mashing,
boiling, fermentation and maturation) and three solideliq-
O. Pinhoa,b, E. Vieiraa and uid separations (wort separation, wort clarification and
J.G. Tavarelaa rough beer clarification) (Wunderlich & Back, 2009).
Barley (Hordeum vulgare) is commonly used as a source
a
REQUIMTE e Serviço de Bromatologia, Faculdade of starch but it has to be malted to dissolve starch in the
de Farmácia da, Universidade do Porto, grains prior to brewing. Malting steps are steeping, germi-
Rua Anibal Cunha 164, 4099-030 Porto, Portugal nation, and kilning. Enzymes digest grain contents during
(e-mail: isabel.ferreira@ff.up.pt) these processes and prepare starch for further processes
b (Celus, Brijs, & Delcour, 2006; Silva et al., 2008). Further,
Faculdade de Ciências da Nutriç~
ao e Alimentaç~ao da,
enzymes convert the starch of milled malt to fermentable
Universidade do Porto, Rua Dr. Roberto Frias,
sugars during mashing. This procedure results in wort
4200-465 Porto, Portugal
that is boiled. Barley malt and adjuncts (substances differ-
ent from barley malt which provide additional fermentable
Saccharomyces yeast biomass is the second major by-product carbohydrates) are the sources of several constituents pres-
from brewing industry. It can be of value as a raw material with ent in beer such as, nitrogenous compounds, lipids, carbo-
different uses, however, it is still underutilized, mostly, for hydrates and vitamins (Bamforth 2002; Ferreira, 2009;
swine and ruminant feed. This review aims to give a brief over- Ferreira & Martins, 2007; Nogueira, Silva, Ferreira, &
view on applications for this agro-industrial by-product as Trugo, 2005; Silva, Ferreira, & Teixeira, 2006; Silva
a source of nutrients for human and fish nutrition, microbial et al., 2008). Hops are added during boiling to provide bit-
growth, production and industrial use of brewer’s yeast com- terness and protect against bacterial spoilage, additionally,
ponents and highlight the needs for further investigations and they are fundamental for good foam formation (Ferreira,
research, especially in the areas of production of ingredients Jorge, Nogueira, Silva, & Trugo, 2005).
for functional foods and the use of brewer’s yeast as agents Yeast converts sugars to alcohol during fermentation of
of detoxifying effluents containing heavy metals. cooled wort. Yeast has a fundamental impact on the quality
of beer. It produces not only ethanol and carbon dioxide but
even other compounds (higher alcohols, organic acids, es-
Origin of brewer’s Saccharomyces yeast biomass
ters, aldehydes, ketones, sulfur compounds) which play
The conventional brewing process has an extremely long
a key role on the sensorial profile of beer (Pinho, Ferreira,
history and can be regarded as a typical example of tradi-
& Santos, 2006). After maturation and storage, beer is fil-
tional biotechnology. Evidence for brewing of beer dates
tered and stabilized.
back to over 8000 years and since then, its pattern and con-
Saccharomyces sensu stricto includes Saccharomyces
sumption has changed considerably. The brewing industry
bayanus, Saccharomyces cariocanus, Saccharomyces cere-
visiae, Saccharomyces kudriavzevii, Saccharomyces mika-
* Corresponding author. tae and Saccharomyces paradoxus (Kurtzman & Robnett,
0924-2244/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tifs.2009.10.008
78 I.M.P.L.V.O. Ferreira et al. / Trends in Food Science & Technology 21 (2010) 77e84

2003) are by far the yeasts most used in the brewing indus-
try. They have several properties that make them outstand-
ing for industrial use and especially the brewing industry,
including fast growth, good ability to produce ethanol and
a tolerance for several environmental stress, such as high
ethanol concentration and low oxygen levels (as reviewed
by Piskur & Langkjaer, 2004).
The yeasts used in breweries are conventionally divided
into two main classes, bottom-fermenting and top-ferment-
ing. Beer is also divided into two very broad categories ac-
cording to which yeast is used, respectively, lager and ale.
Lager yeast, known as Saccharomyces pastorianus or Sac-
charomyces carlsbergensis, runs the fermentation at cool
temperatures (8e15  C), and forms a cloudy mass (floccu-
lates) on the bottom of the vessel (Bamforth, 2003). The
beers so produced are called bottom fermented. Lager beers
Fig. 1. Schematic representation of the Brewers Yeast Biomass valori-
produced by bottom-fermenting yeasts are the most wide- zation through the time.
spread beer types throughout the world (more than 90%).
To produce ale beers, strains of S. cerevisiae are commonly
used in the temperature range of 16e25  C. from Carlsberg Brewery (Denmark) established the basis
The manufacture of beer inevitably involves generation for using selected yeasts strains as starter cultures in brew-
of various residues and by-products that are being produced ing in 1883. He was the first to define ale brewing yeasts
in large amounts annually from main beer manufacturers and to distinguish them from lager brewing yeasts (Rain-
due to increase volume of beer production. Increasing ef- ieri, 2009). Ale yeasts are classified as S. cerevisiae, they
forts are being directed towards the reuse of agro-industrial differ from lager yeasts for their phenotypic and genomic
by-products, from both economic and environmental stand- characteristics. Among the major distinctive traits of these
points (Fillaudeau, Blanpain-Avet, & Daufin, 2006; Mus- yeasts is the ability to ferment well at 20e25  C. Lager
satto, 2009). yeasts are currently classified as S. pastorianus, however,
The yeast is used by the brewer several times (usually their name has changed several times over the years. Han-
4e6 times) and taken from one fermentation to start the sen initially classified them as S. carlsbergensis, in the
next. Nevertheless, brewer’s Saccharomyces yeast biomass 1970s were referred as Saccharomyces uvarum. Lager
is the second major by-product from brewing industry (after stains generally cannot grow above 37  C and ferment
brewer spent grain). Its use is still limited, being basically well at 8e10  C.
used as animal feed. It has received little attention as a mar- The inoculation of wort is called ‘‘pitching’’ and the
ketable commodity, and its disposal is often an environ- pitching rates depend on fermentation temperature. The
mental problem. However, it can be of value as a raw pitching rates most often used are between 15 and 25 mil-
material with different uses. Several attempts have been lion cells/ml (Wunderlich & Back, 2009). During fermenta-
made to use them in biotechnological processes, as for ex- tion, yeast cell mass increases three- to six fold. The
ample in fermentative processes for the production of amount of yeast grown depends on the fermentation condi-
value-added compounds such as ethanol; as substrate for tions of each brewery. The type of yeast as well as the con-
microorganisms cultivation, or simply raw material for ex- dition of the pitching yeast, such as yeast generation and
traction of compounds. This review is designed to highlight glycogen content, can also affect yeast growth. Low fer-
the past, present and emerging applications for this agro-in- mentation beer is produced through two fermentation steps,
dustrial by-product as a source of nutrients for human and the primary fermentation at 8e15  C, followed by a long
fish nutrition, microbial growth, production and industrial secondary fermentation between 1  C and þ4  C (the
use of yeast components as briefly described in Fig. 1. ‘‘lagering phase’’). After primary fermentation 90% of
The use of brewer’s yeast as agents of detoxifying effluents the fermentable matter is consumed and most of the yeast
is a promising potential application that was also is collected as brewer’s Saccharomyces yeast biomass. Af-
summarized. ter beer aging has been completed and the yeast, along with
other insoluble material, has settled, the tank bottoms are
Yeast culture in brewing also collected. Typically, the total amount of brewer’s Sac-
Until the end of the nineteenth century, yeast was not charomyces yeast biomass produced in lager fermentation
identified as the fermentation agent of wort, and beer was is about 1.7 kg/m3e2.3 kg/m3 of final product (Hellborg
traditionally obtained by the action of a mixture of micro- & Piskur, 2009; Huige, 2006). Brewer’s Saccharomyces
organisms, mainly represented by yeasts and bacteria, that yeast biomass usually has 10e14% total solids, including
were perpetuated from one batch to the other. E. C. Hansen yeast solids, beer solids, and trub solids. It may retain as
 I.M.P.L.V.O. Ferreira et al. / Trends in Food Science & Technology 21 (2010) 77e84 79

much as 1.5e2.5% of the total beer production. When yeast supplementation (Balk, Tatsioni, Lichtenstein, Lau, & Pit-
is sold for food uses, removal of both trub solids and beer tas, 2007).
solids is generally necessary. Yeast biomass can be used in food industry to produce
yeast protein concentrates (and isolates) while still retain-
ing their functional properties and nutritive values. Brew-
Aplications for brewer’s Saccharomyces yeast er’s yeast products are usually found in the form of
biomass powders, flakes or tablets, or in liquid form. Liquid yeast
World-wide spent brewer’s yeast is generally sold pri- contains enzymatically digested yeast for better digestion,
marily as inexpensive animal feed after inactivation by absorption and utilization. These products can be sprinkled
heat. Dried yeasts are an excellent source of protein for on food, used as a seasoning or mixed with milk, juices,
swine and ruminant, this application was reviewed recently soups, and gravies.
by Huige (2006). Autolysis by endogenous enzymes occurs naturally in
Commercial brewer’s yeast is inactive yeast (dead yeast yeasts when they complete the cell growth cycle and enter
cells with no leaving power) remaining after the brewing the death phase. In autolysis or self-digestion, the intracel-
process. It is an inexpensive nitrogen source with good nu- lular enzymes break down proteins, glycogen, nucleic
tritional characteristics and a very bitter taste, generally acids, and other cell constituents. The autolytic process re-
recognized as safe (GRAS). Brewer’s yeast should not be quires careful application and control of heat to kill cells
confused with ‘‘brewer’s type yeasts’’ or ‘‘nutritional without inactivating the yeast enzymes. This process is usu-
yeasts’’, which are pure yeasts usually grown on enriched ally carried out under moderate agitation and temperatures
cane or beet molasses under controlled production condi- between 30 and 60  C for 12e24 h. It has some disadvan-
tions, cultivated specifically for use as a nutritional supple- tages such as low extraction yield, difficulty in solideliquid
ment and not a by-product of the brewing process separation due to high content of residue in autolysate, poor
(Bekatorou, Psarianos, & Koutinas, 2006). taste characteristics as a flavour enhancer, and risk of dete-
Interest in microorganism proteins has increased as a re- rioration due to microbial contamination. Plasmolysis, us-
sult of continuously growing fermentation industries which ing inorganic salts such as sodium chloride to accelerate
produce microorganism biomass as a by-product. A limit- autolysis (Belousova, Gordienko, & Eroshin, 1995) has
ing factor in utilization of yeast biomass as a protein source limited use, since there is a growing demand for processed
for human consumption is its high nucleic acid content, pri- foods containing low salt. Hydrolysis is the most efficient
marily ribonucleic acid (RNA), which may account for one method of solubilizing yeast, and is carried out by hydro-
third of the total cell protein. Some reagents and techniques chloric acid or proteolytic enzymes. Despite a high produc-
are used for isolation of yeast protein with low RNA. tion yield, acid hydrolysis is less attractive to the
Yeast biomass is not only a source of proteins but also an manufacturers because of relatively high capital investment
excellent source of B-complex vitamins, nucleic acids, vi- cost, high salt content and high probability of containing
tamins and minerals, including a biologically active form carcinogenic compounds such as monochloropropanol and
of chromium known as glucose tolerance factor. Schwarz dichloropropanol (Huige, 2006). Autolysates and hydroly-
and Mertz (1959) reported that extract of brewer’s yeast sates have several applications as a source of nutrients
could reverse the impaired tolerance to glucose load in and bioactive compounds in aquaculture (summarized in
yeast fed rats. They termed the active substance in brewer’s Table 1).
yeast tolerance factor (GTF). Toepfer, Mertz, Polanski,
Rogenski, and Wolf (1977) reported that the biologically Fish nutrition
active extract from brewer’s yeast contained chromium, Proper nutrition has long been recognized as a critical
nicotinic acid, glycine, cysteine and glutamic acid. They factor in promoting normal growth and sustaining health
provided further evidence for their claim by synthesizing of fish. Brewer’s yeast has been recognized to have poten-
biologically active complexes comprised of trivalent chro- tial as a substitute for live food in the production of certain
mium, nicotinic acid, glycine, cysteine and glutamic acid. fish (Nayar, Hegde, Rao, & Sudha, 1998) or as a potential
Biologically active chromium is trivalent form, which po- replacement for fishmeal (Oliva-Teles & Gonçalves, 2001;
tentiates insulin activity, measured in vitro. Brewer’s yeast Rumsey, Hughes, Smith, Kinsella, & Shetty, 1991; Rumsey,
is a good source of chromium trivalent and has been studied Kinsella, Shetty, & Hughes, 1991). Brewer’s yeast can re-
extensively for its medicinal properties (Cefalu & Hu, place 50% of fishmeal protein with no negative effects in
2004; Ding et al., 2000). Recent studies indicate that no sig- fish performance. Moreover, the inclusion of up to 30%
nificant effect of chromium on lipid or glucose metabolism brewer’s yeast in the diet improved feed efficiency. As
was found in people without diabetes. Chromium supple- a protein feedstuff, brewer’s yeast has been included in
mentation significantly improved glycemia among patients commercial diet formulations for several fish species, in-
with diabetes. However, future studies that address the lim- cluding salmonids.
itations in the current evidence are needed before definitive The cell wall has been suggested to cause the reduced
claims can be made about the effect of chromium nitrogen digestibility commonly found in single cell protein
80 I.M.P.L.V.O. Ferreira et al. / Trends in Food Science & Technology 21 (2010) 77e84

Table 1. Application of autolysates and hydrolysates from brewer’s yeast as a source of nutrients and bioactive compounds in aquaculture.

Brewers yeast Fish spice used Effects References

Intact, disrupted and extracts Rainbow trout (Oncorhynchus Disruption of the cell wall Increases Rumsey, Hughes et al, (1991),
from breweŕs dried yeast mykiss) the digestibility and beneficial effects Rumsey, Kinsella et al. (1991)
Partial replacement of fishmeal Sea bass (Dicentrarchus Brewers yeast can replace 50% of Oliva-Teles and
by brewers yeast, in and in labrax) fishmeal protein with no negative Gonçalves (2001)
isonitrogenous and isoenergetic effects 30% brewers yeast improved
diets feed efficiency No beneficial effects
were observed for supplementation
of brewers yeast diets with methionine
Lyophilised whole yeast Gilthead seabream (Sparus Yeast supplementation improved the Ortuño et al. (2002)
aurata L.) seabream cellular innate immune
response
Yeast Saccharomyces cerevisie Nile tilapia (Oreochromis Improved growth and feed efficiency Lara-Flores et al. (2002)
(0,1%) niloticus) appropriate growth stimulating additive
Dried brewers yeast (Brewtech Ò) Hybrid striped bass (Morone Positively influenced growth performance Li and Gatlin (2003, 2004)
Incremental levels 1%, 2%, 4% chrysops  M. saxatilis) and feed efficiency Resistance to
Streptococcus iniae infection
Yeast-based prebiotic mixture Hybrid striped bass (Morone Immunostimulation and enhanced Li and Gatlin (2005)
GroBioticÒ chrysops  M. saxatilis) resistance to S. iniae and Mycobacterium
marinum
GroBiotic-A, brewer’s yeast and Red drum (Sciaenops ocellatus) Positive effect on immune response, Burr et al. (2008)
fructooligosaccharide disease resistance and intestinal microbial
community
Brewer’s yeast and GroBioticÒ-A Pacific white shrimp (Litopenaeus Dietary supplementation of GroBioticÒ-A Li et al. (2009)
(each component was vannamei) improved survival of shrimp cultured
supplemented at 2% or 5%) at low-salinity (2 ppt).
Brewers yeast commercial Fish and crustacean larvae Low-cost technology for mass production Ricci et al. (2003)
formulations to feed living of the free-living nematode P. redivivus as
Panagrellus redivivus an alternative live food for first feeding fish
and crustacean larvae

sources (Yamada & Sgarbieri, 2005). Disruption of the cell relatively long periods without causing immunosuppression
wall increases the digestibility and beneficial effects of di- (Li & Gatlin, 2003, 2004, 2005).
ets containing brewer’s dried yeast fed to rainbow trout Additionally, brewer’s yeast commercial formulations is
(Rumsey, Hughes et al., 1991; Rumsey, Kinsella et al., suitable as a food source for the mass production of the
1991). nematode Panagrellus redivivus used for feeding farm
Farmfish diets should not only provide the essential nu- fish and crustacean larvae (Ricci, Fifi, Ragni Schlechtriem,
trients that are required for normal physiological function- & Focken, 2003) during their early stages of development.
ing but may serve as the medium by which fish receive
other components that may affect their health (Gatlin,
1997, 2002; Webster, 2002). Brewer’s yeast contains vari- Microorganisms’ substrate
ous immunostimulating compounds such as b-glucans, Owing to the high level of protein, vitamin B complex
nucleic acids as well as mannan oligosaccharides (White, and minerals, brewer’s yeast cells, its autolysates and hy-
Newman, Cromwell, & Lindemann, 2002). It has been drolysates might be used as a nutrient source for the growth
observed to be capable of enhancing immune responses of fastidious microorganisms or related product formation.
(Ortuño, Cuesta, Rodrı́guez, Esteban, & Meseguer, 2002; Consequently, there is an economic interest in using these
Siwicki, Anderson, & Rumsey, 1994) as well as growth yeast extracts in microbiological media and several studies
(Lara-Flores, Olvera-Novoa, Guzmán-Méndez, & López- were performed to evaluate growth-promoting properties of
Madrid, 2002) of various fish species and thus may serve brewer’s yeast extracts as summarized in Table 2. The
as an excellent health promoter for fish culture. Brewer’s effect of brewers’ yeast extracts pure or mixed with baker’s
yeast positively influenced growth performance and feed extracts were evaluated on the growth of lactobacilli
efficiency of hybrid striped bass as well as resistance to and pediococci (Lactobacillus casei EQ28 and EQ85,
Streptococcus iniae infection. Several experiments describe Lactobacillus acidophilus EQ57, Pediococus acidilactici
the influence of dietary additives on immune response, MA18/5-M) to provide information for industry that formu-
disease resistance and intestinal microbial community late microbiological growth media, as well as to producers
(Burr, Hume, Ricke, Nisbet, & Gatlin 2008; Li et al., of yeast extracts. Growth of L. acidophilus EQ57 was
2009). In addition, results of immune response assays dem- best in the presence of 100% (Champagne, Gaudreau, &
onstrate that brewer’s yeast can be administered for Conway, 2003).
 I.M.P.L.V.O. Ferreira et al. / Trends in Food Science & Technology 21 (2010) 77e84 81

Table 2. Application of autolysates and hydrolysates from brewer’s yeast as a source of nutrients in microbiological media.

Brewers yeast Microorganisms Effects Application References

Brewers yeast extracts Lactobacillus casei EQ28 Only for L. acidophilus Formulation of Champagne et al.
pure or mixed with and EQ85, Lactobacillus EQ57 growth was best microbiological (2003)
bakers yeast acidophilus EQ57, in the presence 100% growth media.
Pediococus acidilactici brewers yeast
MA18/5-M
Mixture of beetroot Lactobacillus plantarum L. plantarum A112 and Functional additive Rakin et al.
juice and autolysates A112, L. acidophilus L. acidophilus BGSJ15-3 in a form of beverages, (2004)
of brewers yeast BGSJ15-3 L. acidophilus can be successfully used power or tablets
NCDO1748 for fermentation of the
mixture of beetroot juice
and brewer’s yeast autolysate
Mixture of beetroot L. acidophilus Higher mineral content in Functional additive in a Rakin et al.
juice, carrot juice and NCDO1748 the carrot juice better form of beverages, (2007)
autolysates of brewers improved production of power or tablets
yeast lactic acid
Crude yeast autolysate Recombinant bacterium Increase the ethanol Ethanol production York and Ingram
supplemented with Escherichia coli KO11 formation (1996)
minerals and vitamins
Brewers yeast Actinobacillus Enzymatic hydrolysis was a Production of succinic Jiang et al.
hydrolysate succinogenes NJ113 more effective method due acid for preparation of (2009)
or autolysate to the higher succinic acid biodegradable polymers
yield and cell growth
Hydrothermal Saccharomyces The growth of yeast cells in Hydrothermal decomposition Lamoolphak et al.
decomposition of cerevisiae the culture medium containing of yeast cells for production (2006)
proteins from 2 w/v% of this products was of proteins and amino acids
brewers yeast comparable to that of the cells
grown in the medium containing
commercial yeast extract at the
same concentration

The importance of functional foods in the world is in- Actinobacillus succinogenes NJ113 in glucose-containing
creasing, and the procedures for their production are under media to develop a cost-effective fermentation medium.
intense development. A functional food additive based on Autolysis and enzymatic hydrolysis were used to hydrolyze
beetroot juice (Beta vulgaris L.) using brewer’s yeast autol- the spent brewer’s yeast cells to release the nutrients. The
ysate and fermented by Lactobacillus plantarum A112, L. results showed that enzymatic hydrolysis was a more effec-
acidophilus BGSJ15-3 and L. acidophilus NCDO1748 is tive method due to the higher succinic acid yield and cell
described (Rakin, Baras, & Vukasinovic, 2004). Beetroot growth (Jiang et al., 2009).
was chosen as a starting substance for the production of bi- The decomposition of proteinaceous material from
ologically highly valuable food, as there are numerous pub- brewer’s yeast waste to obtain more useful products is an-
lications describing its favourable nutritive and protective other possibility of using this by-product. Recently, the hy-
benefits on humans. Fermentation using lactic acid bacteria drothermal decomposition into protein and amino acids of
is a widespread tradition. Brewer’s yeast autolysate contrib- baker’s yeast cells was used as a model for spent brewer’s
utes to the increase of the number of viable cells of lactic yeast waste. The reaction was carried out in a closed batch
acid bacteria during the fermentation. L. plantarum A112 reactor at various temperatures between 100 and 250  C.
and L. acidophilus BGSJ15-3 can be successfully used for The hydrolysis product obtained at 200  C was tested as
this purpose. a nutrient source for yeast growth. These results demon-
The same authors used autolysates of brewer’s yeast strated the feasibility of using subcritical water to poten-
cells for lactic acid production by L. acidophilus tially decompose proteinaceous waste such as spent
NCDO1748 in beetroot and carrot juices enriched with brewer’s yeast while recovering more useful products (La-
brewer’s yeast autolysate, in order to improve the nutritive moolphak, et al., 2006).
and protective properties of the product (Rakin, Vukasi-
novic, Siler-Marinkovic, & Maksimovic, 2007). Food ingredients
Concerning the use of autolysates and for product for- Other possibilities of application are the production and
mation, brewer’s yeast autolysate has been used for ethanol industrial use of yeast components, such as nucleic acids,
production by recombinant Escherichia coli (York & In- nucleotides, cell wall polysaccharides and others. The utili-
gram, 1996). Spent brewer’s yeast hydrolysate was evalu- zation of the brewer’s yeast cells from beer industry for the
ated as a nitrogen source for succinic acid production by production of food-grade yeast extract is promising, for
82 I.M.P.L.V.O. Ferreira et al. / Trends in Food Science & Technology 21 (2010) 77e84

example, to obtain flavouring foodstuff. Flavouring en- industrial scale, parameters for the scale-up production of
hancers, monosodium glutamic acid (MSG) and nucleo- the enzyme will have to be carefully studied.
tides such as 50 -guanosine monophosphate (50 -GMP) and On the other hand, yeast cells represent an inexpensive,
50 -inosine monophosphate (50 -IMP) are well known in the readily available source of biomass that has a significant
food processing. Yeast extract from dried brewer’s yeast potential for dye bioaccumulation. Modification of yeast
cells can be used by enzymatic treatment in a wide variety cells with the perchloric acid stabilized ferrofluid lead to
of foods as flavors, flavour enhancers, or flavour potentia- the formation of magnetically responsible material, which
tors. Uses include meat products, sauces and gravies, soups, could be used as an efficient adsorbent for the removal of
chips and crackers (Chae, Joo, & In, 2001; Halasz & Lász- various water-soluble dyes (Safariková, Ptácková, Kibri-
tity, 1991; Huige, 2006). ková, & Safarik, 2005).
b-Glucan obtained from brewer’s yeast can be used in The use of inexpensive biosorbents to sequester heavy
food products as a thickening, water-holding, or oil-binding metals from aqueous solutions, is one of the most promis-
agent and emulsifying stabilizer (Thammakiti, Suphanthar- ing technologies being developed to remove these toxic
ika, Phaesuwan, & Verduyn, 2004). Brewer’s yeast was au- contaminants from wastewaters. Considering this chal-
tolysed and the cell walls were homogenized, extracted lenge, the viability of Cr(III) and Pb(II) removal from aque-
firstly with alkali, then with acid, and then spray dried. Ef- ous solutions using a flocculating yeast residual biomass
fects of the homogenization on the chemical composition, from a brewing industry was studied (Ferraz, Tavares, &
rheological properties and functional properties of b-glucan Teixeira, 2004). Yeast biomass showed higher selectivity
were investigated. Homogenized cell walls exhibited higher and uptake capacity to lead. Still, these results were far
b-glucan content and apparent viscosity than those which from ideal, being necessary to make more detailed studies
had not been homogenized because of fragmentation of to reach maximum recovery.
the cell walls. The use of nonliving biomass of yeast Saccharomyces as
Use of prebiotics, nondigestible dietary ingredients that a suitable biosorbent of metal ions (lead, zinc, copper, and
beneficially affect the host by selectively stimulating the nickel) is also reported. Heat-killed cells showed a higher
growth of and/or activating the metabolism of health-pro- degree of heavy metal removal than live cells, being
moting bacteria in the intestinal tract, is a novel concept more suitable for bioremediation works. Dead flocculent
in aquaculture. This phenomenon is worth exploring not cells can be used in a low-cost technology for detoxifying
only in human but also in fish nutrition. With the increasing metal-bearing effluents as this approach combines an effi-
concerns about use of antibiotics in aquaculture, various cient metal removal with the ease of cell separation (Ma-
pre- and probiotics should receive further consideration. chado, Janssens, Soares, & Soares, 2009; Machado,
How to utilize dietary strategies and prebiotics to maximize Santos, Gouveia, Soares, & Soares, 2008; Parvathi, Nagen-
the efficiency of probiotics is a promising subject and more dran, & Nareshkumar, 2007; Zouboulis, Matis, & Lazaridis,
research is warranted. 2001). The application of S. cerevisiae as a biosorbent not
only removes metals from wastewaters but also eases the
burden of disposal costs associated with the waste. How-
Future trends ever, literature on the application of biosorption to ‘‘real’’
The Saccharomyces yeast cells contain, numerous en- industrial effluents is still scarce.
zymes, namely, vacuolar proteases including serine, aspar-
tyl, and metallo proteases, pectinases among others, thus,
the industrial production of these enzymes from brewer’s References
yeast is a field to explore. However, until now studies Balk, E. M., Tatsioni, A., Lichtenstein, A. H., Lau, J., & Pittas, A. G.
were performed only with S. cerevisiae ATCC 52712. (2007). Effect of chromium supplementation on glucose metabo-
lism and lipids. A systematic review of randomized controlled tri-
The suitability of crude yeast pectinase for fruit juice ex-
als. Diabetes Care, 30, 2154e2163.
traction was reported for to aid pineapple juice extraction Bamforth, C. (2003). Yest and fermentation. Beer: Tap into the art and
(Dzogbefia, Ameko, Oldham, & Ellis, 2001). science of brewing. New York: Oxford University Press, pp. 144e159.
Rapid extraction of pawpaw juice with the application of Bamforth, C. W. (2002). Nutritional aspects of beer e a review. Nu-
locally produced pectic enzymes from S. cerevisiae ATCC trition Research, 22, 227e237.
Bekatorou, A., Psarianos, C., & Koutinas, A. (2006). Production of food
52712 and combined effects of enzyme dosage and reaction
grade yeasts. Food Technology and Biotechnology, 44(3), 407e415.
time on papaya juice extraction are also reported (Djokoto, Belousova, N. I., Gordienko, S. V., & Eroshin, V. K. (1995). Influence of
Dzogbefia, & Oldham, 2006; Dzogbefia & Djokoto, 2006). autolysis conditions on the properties of amino-acid mixtures
The suitability of this enzyme for starch production at a lo- produced by ethanol-assimilating yeast. Applied Biochemistry
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