34.5 Biochemicals

525

AFW in the treatment of polluted water bodies has been dealt with extensively in

the book chapter of Abosede [36].

The role of microorganisms toward valorization of AFW is noteworthy. Microbial

solutions for AFW valorization have distinct advantages like being environmental-

friendly, reliable and cost-effective as compared to other approaches. Biocolorants

have been produced by the fermentation of bakery waste using the fungal strain

Monascus purpureus [37]. Agri-food residues have also been used as substrates for

the production of biopesticides from Bacillus thuringiensis (Bt) [38, 39]. Xylitol is

another biochemical produced by many microorganisms by the fermentation of

xylose present in hemicellulosic hydrolysates derived from AFW [40]. Commercial

production of ethanol and tartaric acid is possible from wine lees [41, 42]. Organic

fraction of municipal solid wastes like household food wastes, food waste from

cafeteria, citrus waste, grape pomace, potato peel waste, pineapple and banana peel

have also been used successfully to produce ethanol [43]. Attempts for recovery

of other bioactive compounds like phenolic compounds [44] squalene [45] and

also to use wine lee as supplement in lactic fermentations are also known [46].

Fermentations have also been used to produce succinic, citric, lactic acids, butanol

and poly-3-hydroxybutyrate (P3HB) from food waste [47].

Microbial oils have been produced through the valorization of kitchen waste from

households which in turn can be used for the production of biodiesel and various

oleochemicals such as biolubricants and wax esters [48], while bacterial cellulose

has been produced from pineapple pomace, tomato wastes and coconut water using

Acetobacter xylinum [49] which have applications in medical, textiles, cosmetics and

food sectors.

34.5.3

Enzymes

AFWs are also important sources of enzymes. Enzymes are a key ingredient ensuring

the success of the biorefinery concept. Conventional production of enzymes is com-

plex but when produced on AFW employing solid-state fermentation can prove to

be economical [50–55]. Kitchen and domestic wastes have been used as substrates to

produce a wide variety of enzymes like glucoamylase, pectinolytic enzymes, lipase,

cellulose, glucoamylases and proteases via solid-state fermentation involving fun-

gal strains [43, 56]. However, studies and technological interventions to make the

process more economically viable are needed.

34.5.4

Foods/Feeds/Supplements

Some of the AFWs generated by industries have the potential to be directly used

in human foods. Brewers spent grain, a byproduct of the brewing industry rich in

arabinoxylan, lignin, cellulose [57], proteins [58], can be directly used to increase

the fiber, protein and calorific contents of bread and baked snacks [59]. This is also

known to improve the technological and nutritive properties of breads. Such type

of supplementation should also consider the synergetic and antagonistic effects of

phenolic compounds derived from the incorporated wastes and bread ingredients as