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28 Bioconversion of Food Waste to Wealth – Circular Bioeconomy Approach

and from 10.14% to 18.10% for cellulose. Solid–liquid fat extraction pretreatment

technique provided high sugar yield and high degradation of starch and cellulose

by enzymatic hydrolysis.

Utilizing food waste as animal feed is a successful alternative technique to landfill.

Food waste was given as pig feed many decades, but sometimes the presence of meat

in food waste and non-heat-treated food waste could end up with foot-and-mouth

disease and African swine fever. In 2001, the outbreak of foot-and-mouth disease

caused a crisis in British agriculture and farm, by slaughtering more than 6 million

animals, costing 8 billion pounds to the public and private sector. Enzymatic diges-

tion helps in digesting the food waste into pasteurized feed with more digestible

nutrients like free sugars, amino acids, and fatty acids. Pandey et al. [53] converted

food waste into organic soil amendments (OSAs) by three stages starting from (i)

enzymatic digestion, (ii) pasteurization, and (iii) acidification. The developed OSA

can be used as an effective fertilizer (chemical and pathogen-free), and authors

revealed 25% increase in growth rate for the strawberry plant. Further, the byprod-

uct of this process can be potentially used as feed for pork or chicken. Authors

succeeded in converting food waste to OSA with a non-detectable level of pathogens

(Escherichia coli O157: H7, Salmonella LT2, and Listeria monocytogenes). Later,

Jinno et al. [47] took a step further by feeding the enzymatic digested food waste to

the growing pigs and compared with the control diet (based on corn and soybean

meal). There was no significant difference in body weights between the control

and enzymatic digested food waste. For instance, a pig weighed between 32 and

–33.6 kg on day 1 was grown to 108.15 kg (control diet) and 98.77 kg (for enzymatic

digested food waste). One can observe that animal feed from enzyme-treated food

waste should be able to provide necessary nutrients and can be effectively used as a

substitute for corn or soy compositions in their diet.

28.4.3.1

Enzyme Immobilization Technology

The application of enzymes in valorizing food waste has numerous advantageous

over the conventional chemical process. However, it is important to note the major

issues in maintaining the stability and activity of enzymes due to the non-favorable

environment for enzymes like non-neural pH and higher temperature. Enzyme

immobilization technology is tailored to improve the enzyme catalytic features like

activity, selectivity, and resistance to inhibitors [54]. Immobilizing enzymes on a

solid support or cross-linking via enzyme–enzyme will improve the performance

and stability and also enable the reuse of enzymes. This enzyme immobilization

technique is in use from 1960s, and the past six decades of research and industrial

practice has abandoned the tedious trial-and-error approach and brought the

rational approach for designing immobilized enzymes [55]. Several immobilization

strategies can be used like entrapment, adsorption, covalent binding, ionic binding

or metal-linked immobilization, and the selection of immobilization technique is

depending on the physicochemical characteristics of enzyme, support material,

and substrate matrix. Further, the selection of support material should possess

high physical stability (mechanical strength), chemical stability, and biological

stability during processing, inert on immobilized enzyme and the target analyte,

and adequate functional groups for effective binding of enzymes and achieve high

loading capacity and biodegradability.