Sustainable bioconversion of food waste into high-value products by immobilized enzymes to meet bio-economy challenges and opportunities – A review (original) (raw)

Food Research International

Over the past few years, food waste has intensified much attention from the local public, national and international organizations as well as a wider household territory due to increasing environmental, social and economic concerns, climate change and scarcity of fossil fuel resources. On one aspect, food-processing waste represents a substantial ecological burden. On the other hand, these waste streams are rich in carbohydrates, proteins, and lipids, thus hold significant potential for biotransformation into an array of high-value compounds. Indeed, the high sugar, protein, and fat content render food waste streams as attractive feedstocks for enzymatic valorization given the plentiful volumes generated annually. Enzymes as industrial biocatalysts offer unique advantages over traditional chemical processes with regard to eco-sustainability, and process efficiency. Herein, an effort has been made to delineate immobilized enzyme-driven valorization of food waste streams into marketable products such as biofuels, bioactive compounds, biodegradable plastics, prebiotics, sweeteners, rare sugars, surfactants, etc. Current challenges and prospects are also highlighted with respect to the development of industrially adaptable biocatalytic systems to achieve the ultimate objectives of sustainable manufacturing combined with minimum waste generation. Applications-based strategies to enzyme immobilization are imperative to design cost-efficient and sustainable industrially applicable biocatalysts. With a deeper apprehension of support material influences, and analyzing the extreme environment, enzymes might have significant potential in improving the overall sustainability of food processing. 1. Introduction, current context, and drivers In the food processing industries, waste is generated by the separation of target products from undesired by-products (Kwan et al., 2018). In recent years, massive research efforts have been made in utilizing food-processing waste (FPW) to produce high-value bioproducts. A sustainable bioconversion of food waste into valuable products not only offer economic advantages but also abates nuisances generated by food waste decomposition in the surroundings and landfills. The major requisite features that enable the use of food-based waste materials are shown in Fig. 1. Food-processing waste may be produced in liquid, solid, or semi-solid forms. Liquid wastes are generated because of the use of huge amounts of water for specific applications such as cleaning, sanitation, temperature regulation, transportation, cooking and as auxiliary water. The resulting effluent contains organic matter, suspended solids, nitrogen, fats, oils, and many other inorganic materials. Common liquid effluents comprised potato-processing wastewater, apple residue sludge, whey from the manufacturing of the cheese, yogurt and tofu, bakery, brewery, oil mill, and soda industry effluent, etc. On the other hand, major solid wastes are potato and tomato waste, waste bread, apple/grape pomace, and soybean curd residue. The solid food wastes are loaded with lignin, cellulose, starch, and monosaccharides (i.e., glucose and fructose) as compared to liquid food wastes containing nutrients in diluted form (Bilal et al., 2018; Hegde, Lodge, & Trabold, 2018). Inevitable rising fossil fuel prices, dwindling natural resources and increasing prices of raw materials together with growing worldwide demand for energy, biofuels, chemicals, and biomaterials in our society are the key drivers to develop environmentally-friendly technologies based on cheaper and sustainable feedstocks to achieve such global target. Production of biofuels utilizing alternative feedstocks to conventional fossil raw materials, i.e. lignocellulosic raw materials has