Using algae cells to drive cofactor regeneration and asymmetric reduction for the synthesis of chiral chemicals

Asymmetric reduction of prochiral ketones via biocatalysis is the most effective method for the synthesis of chiral alcohols. The industrial biocatalytic reduction process requires additional co-substrates and enzymes, e.g., glucose and glucose dehydrogenase, to regenerate reductive cofactors, such as nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH), for efficient substrate conversion and product yield. Thus, increasing the cost in reaction and downstream treatment. Recently, algae cells, due to a combination of microorganism-like properties (rapid growth and high density culture) and plant-like properties (highly active photosynthesis), have attracted much attention as novel host cells in industrial biocatalysis. Particularly, autotrophic photosynthesis in algae is capable of regenerating NADH and NADPH rapidly, eliminating the requirement of additional enzymes and co-substrates for cofactor regeneration in normal biocatalytic processes. Recently, a variety of algae species, such as cyanobacteria, green algae, diatoms, chrysophytes, and red algae, have been applied in asymmetric biocatalysis. Herein, various asymmetric reduction reactions performed by different type of algae cells have been reviewed, and methods for improving the reaction efficiency have been discussed. We aim to attract algae microbiologists and chemists to push forward the study of algae as biocatalytic cell factories for value-added industrial chemical production in the future.