Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres Review Sustainable bioconversion of food waste into high-value products by immobilizedenzymestomeetbio-economychallengesandopportunities–A review Muhammad Bilal a, ⁎ ,HafzM.N.Iqbal b, ⁎ a School of Life Science and Food Engineering, Huaiyin Institute of Technology, Huaian 223003, China b Tecnologico de Monterrey, School of Engineering and Sciences, Campus Monterrey, Ave. Eugenio Garza Sada 2501, Monterrey, N.L. CP 64849, Mexico ARTICLEINFO Keywords: Food industry waste Green biotechnology Enzyme Immobilization Biocatalysis Bioconversion High-value products ABSTRACT Over the past few years, food waste has intensifed much attention from the local public, national and inter- national organizations as well as a wider household territory due to increasing environmental, social and eco- nomic concerns, climate change and scarcity of fossil fuel resources. On one aspect, food-processing waste re- presents a substantial ecological burden. On the other hand, these waste streams are rich in carbohydrates, proteins,andlipids,thusholdsignifcantpotential forbiotransformationintoanarrayofhigh-valuecompounds. Indeed,thehighsugar,protein,andfatcontentrenderfoodwastestreamsasattractivefeedstocksforenzymatic valorization given the plentiful volumes generated annually. Enzymes as industrial biocatalysts ofer unique advantagesovertraditionalchemicalprocesseswithregardtoeco-sustainability,andprocessefciency.Herein, an efort has been made to delineate immobilized enzyme-driven valorization offoodwastestreamsintomar- ketable products such as biofuels, bioactive compounds, biodegradable plastics, prebiotics, sweeteners, rare sugars,surfactants,etc.Currentchallengesandprospectsarealsohighlightedwithrespecttothedevelopmentof industrially adaptable biocatalytic systems to achieve the ultimate objectives of sustainable manufacturing combined with minimum waste generation. Applications-based strategies to enzyme immobilization are im- perativetodesigncost-efcientandsustainableindustriallyapplicablebiocatalysts.Withadeeperapprehension of support material infuences, and analyzing the extreme environment, enzymes might have signifcant po- tential in improving the overall sustainability of food processing. 1. Introduction, current context, and drivers In the food processing industries, waste is generated by the se- paration of target products from undesired by-products (Kwan et al., 2018). In recent years, massive research eforts have been made in utilizing food-processing waste (FPW) to produce high-value biopro- ducts.Asustainablebioconversionoffoodwasteintovaluableproducts notonlyofereconomicadvantagesbutalsoabatesnuisancesgenerated by food waste decomposition in the surroundings and landflls. The major requisite features that enable the use of food-based waste ma- terialsareshownin Fig.1.Food-processingwastemaybeproducedin liquid, solid, or semi-solid forms. Liquid wastes are generated because of the use of huge amounts of water for specifc applications such as cleaning, sanitation, temperature regulation, transportation, cooking and as auxiliary water. The resulting efuent contains organic matter, suspended solids, nitrogen, fats, oils, and many other inorganic materials. Common liquid efuents comprised potato-processing was- tewater, apple residue sludge, whey from the manufacturing of the cheese, yogurt and tofu, bakery, brewery, oil mill, and soda industry efuent,etc.Ontheotherhand,majorsolidwastesarepotatoandto- mato waste, waste bread, apple/grape pomace, and soybean curd re- sidue. The solid food wastes are loaded with lignin, cellulose, starch, andmonosaccharides(i.e.,glucoseandfructose)ascomparedtoliquid 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 demandforenergy,biofuels,chemicals,andbiomaterialsinoursociety 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 con- ventional fossil raw materials, i.e. lignocellulosic raw materials has https://doi.org/10.1016/j.foodres.2019.04.066 Received19February2019;Receivedinrevisedform15April2019;Accepted29April2019 ⁎ Corresponding authors. E-mail addresses: bilaluaf@hotmail.com (M. Bilal), hafz.iqbal@tec.mx (H.M.N. Iqbal). Food Research International 123 (2019) 226–240 Available online 30 April 2019 0963-9969/ © 2019 Elsevier Ltd. All rights reserved. T