Catalytic Performance of a Robust Whole-Cell Biocatalyst in the Regioselective Synthesis of Helicid Esters Under Optimized Processing Conditions

In this study, lyophilized Pseudomonas aeruginosa based whole-cell biocatalyst was used in the highly efficient and regioselective acylation of helicid with fatty acid vinyl esters in organic solvents. P. aeruginosa whole-cell catalyst showed high biomass and biocatalytic performance using 0.1% (w/v) soybean oil and 0.2% (w/v) tryptone as the carbon and nitrogen source, respectively. The biomass (0.72 g/L) cultivated for 36 h under the optimized conditions was 2-folds higher than that obtained by the use of the initial conditions (0.36 g/L). In addition, the optimized medium was found to be suitable for P. aeruginosa cultured in 3.5-L scale fermentation with high biomass (0.71 g/L) obtained at 24 h. Besides, a high substrate conversion efficiency (ranged from 92 to 99%) and excellent regioselectivity (99%) was achieved when P. aeruginosa whole-cell biocatalyst was applied to synthesize an array of 6′-esters of helicid. The reaction rate varies with varying acyl donors because of their differential interactions with the catalytic site of the enzyme from the whole cells of P. aeruginosa . Taken together, P. aeruginosa whole-cell catalyst obtained using optimal culture medium manifest a promising and highly-regioselective alternative to purified enzymes for the regioselective formation of 6′-esters derivatives of helicid in non-aqueous solvents. Graphic Abstract