LAUSR

Abstract Photo‐ and biocatalysis show many advantages as more sustainable solutions for the production of fine chemicals. In an effort to combine the benefits and the knowledge of both these areas, a continuous photobiocatalytic setup was designed and optimized to carry out whole‐cell biotransformations within cells of the cyanobacterium Synechocystis sp. PCC 6803 expressing the gene of the ene‐reductase YqjM from B. subtilis. The effect of the light intensity and flow rate on the specific activity in the stereoselective reduction of 2‐methyl maleimide was investigated via a design‐of‐experiments approach. The cell density in the setup was further increased at the optimal operating conditions without loss in specific activity, demonstrating that the higher surface area/volume ratio in the coil reactor improved the illumination efficiency of the process. Furthermore, different reactor designs were compared, proving that the presented approach was the most cost‐ and time‐effective solution for intensifying photobiotransformations within cyanobacterial cells.