Enzymes, In Vivo Biocatalysis, and Metabolic Engineering for Enabling a Circular Economy and Sustainability

Abstract

Since the industrial revolution, the rapid growth and development of global industries have depended largely upon the utilization of coal-derived chemicals, and more recently, the utilization of petroleum-based chemicals. These developments have followed a linear economy model (produce, consume, and dispose). As the world is facing a serious threat from the climate change crisis, a more sustainable solution for manufacturing, i.e., circular economy in which waste from the same or different industries can be used as feedstocks or resources for production offers an attractive industrial/business model. In nature, biological systems, i.e., microorganisms routinely use their enzymes and metabolic pathways to convert organic and inorganic wastes to synthesize biochemicals and energy required for their growth. Therefore, an understanding of how selected enzymes convert biobased feedstocks into special (bio)chemicals serves as an important basis from which to build on for applications in biocatalysis, metabolic engineering, and synthetic biology to enable biobased processes that are greener and cleaner for the environment. This review article highlights the current state of knowledge regarding the enzymatic reactions used in converting biobased wastes (lignocellulosic biomass, sugar, phenolic acid, triglyceride, fatty acid, and glycerol) and greenhouse gases (CO 2 and CH 4 ) into value-added products and discusses the current progress made in their metabolic engineering. The commercial aspects and life cycle assessment of products from enzymatic and metabolic engineering are also discussed. Continued development in the field of metabolic engineering would offer diversified solutions which are sustainable and renewable for manufacturing valuable chemicals.

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“…[22] The chimeric enzyme minimized the oxidative damage caused by peroxide resulting in the prolonged activity of OleT JE compared to the wild-type system. [22,23]…”

“…To overcome such challenge, a fusion system comprising of OleT JE and a H 2 O 2 generating Alditol oxidase was recently used [22] . The chimeric enzyme minimized the oxidative damage caused by peroxide resulting in the prolonged activity of OleT JE compared to the wild‐type system [22,23] …”

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“…Mandelic acid and its derivatives (MADs) are such a series of chiral compounds that have attracted much attention due to their wide use in the synthesis of antibiotics, antiobesity and antitumor agents, biologically active compounds and enantiomer separation. 1,2 Due to their superior water solubility, the concentration of MADs is substantial in relevant wastewater, causing serious environmental problems because of their strong negative environmental impact and high toxicity. 3 Considering not only environmental pollution improvement but also resource re-utilization, converting MADs into useful chemicals, i.e.…”