Prroduction System for Carbon Recyclable Green Plastics Based on Enzyme Evolutionary Engineering

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Polyhydroxyalakanoates (PHAs) form a class of natural polyesters that many microorganisms in the environment accumulate in the form of intracellular granules to store carbon and reducing equivalents. The wide variety of monomers yields PHAs with diverse material properties that depend on polymer composition. Besides the practical applications of PHAs as bioplastics that are biodegradable and made from renewable resources, from the standpoint of an academic metabolic pathway engineer. PHAs are model compounds for metabolic engineering. The primary aims of the metabolic engineering of PHAs include controlling different factors that determine polymer material properties, such as monomeric compositions, molecular weight and copolymer microstructure, as well as optimizing yield. Pathway engineering for PHA production offers the opportunity to synthesize novel polymers with desirable properties in low-cost, high-productivity fermentations. Most recently, enzyme evolution is becoming the new … More approach for PHA production. A break-through in the chemical synthesis of macromolecules with desirable properties was achieved by the development of prominent chemical catalysts via "catalyst evolution". Thus, one can easily accept the concept that the molecular evolution of the biocatalysts (enzymes) relevant to PHA synthesis will provide us with a chance to create novel PHA materials with high performance. The enzyme evolution-aided PHA production system be involved in the carbon ecosystem. In this study, I demonstrated the case studies of enzyme engineering for optimization of productivity and regulation of monomeric composition of PHA. Rational molecular design was applied to monomer supplying enzyme based on three dimensional structure of PhaJ and evolutionary engineering was applied to PHA synthase based on functional mapping. A huge amount of library of enzyme mutants, created through engineering of these key enzymes for PHA biosynthesis, can provide tailor-made biopolymers with diverse properties suitable for wide-range applications. Transferring mutants to the plant system has been performed. Less