Study On The Catalytic Performance Of Synechocystis And Chlamydomonas Reinhardtii In Asymmetric Reduction Of Carbonyl Groups

Chiral alcohols are widely used in the synthesis of medicines,pesticides,flavors and fragrances and other fine chemicals.The green and efficient synthesis of chiral alcohols is the key to the large-scale manufacturing of chiral products.Biocatalytic asymmetric reduction of prochiral carbonyl compounds is widely used in the production of chiral alcohols.Microalgae is a new type of host cell in the field of biocatalysis.It not only contains abundant carbonyl reductase,but also regenerates coenzymes by photosystem like green plants,providing reducing power for asymmetric catalytic reactions.First,this paper studied the substrate tolerance,substrate specificity and selectivity of two model strains of Synechocystis sp.PCC 6803 and Chlamydomonas reinhardtii CW15 to 10 aromatic compounds.The results showed that the tolerable concentration of Synechocystis sp.PCC 6803 to 10 kinds of substrates was 1.5-2 times higher than that of Chlamydomonas reinhardtii CW15,and it was found that the tolerance of the two kinds of algae to substrates containing halogen element chlorine was lower than that of other substrates.In addition,due to the different enzyme systems in different microalgae cells,the overall enantiomeric excess of Synechocystis for 10 kinds of substrates is slightly higher than that of Chlamydomonas reinhardtii,and e.e.of the Chlamydomonas reinhardtii catalytic product was 73%-95%,while the e.e.of Synechocystis catalyzed product is 81%-99%.Secondly,meta-chloroacetophenone and 3'methylacetophenone were chosen as the model substrates of Synechocystis sp.PCC 6803 and Chlamydomonas reinhardtii CW15,respectively.Different reaction conditions,such as temperature,light,substrate concentration,etc were discussed.For meta-chloroacetophenone,the conversion rate and e.e.reached 95%and 99%,respectively,after 48 hours of reaction under the optimal conditions.For 3'methylacetophenone,he conversion rate and e.e.of Chlamydalis were 90%and 95%,respectively,after 48h reaction under the optimal conditions.Finally,microalgae mainly drive coenzyme regeneration through photosynthesis,and the content and regeneration efficiency of NADPH in microalgae cells directly affect the catalytic efficiency.By constructing a mutant strain of Synechocystis with the deletion of the gene phaC&E,the consumption of NADPH in the PHB pathway was reduced,and the content of NADPH in the mutant strain was increased by 2.7 times,but the catalytic efficiency was not significantly improved.In addition,by adding compounds to the catalytic system of Synechocystis and Chlamydomonas reinhardtii to regulate the regeneration and consumption of intracellular NADPH,the NADPH content in the Synechocystis increased by up to 25%,and the NADPH content in the Chlamydomonas reinhardtii increased by up to 2.4 times.The reaction time to reach the maximum conversion rate is shortened by 12 hours.This article lays a theoretical foundation for the preparation of chiral chemicals by autotrophic algae cells in the field of photocatalysis by recycling NADPH,and provides guidance for the subsequent in-depth exploration of microalgae biocatalysis capabilities and large-scale industrial applications.