Optimization of enzymatic synthesis of L-ascorbyl palmitate by solvent engineering and statistical experimental designs

Statistical experimental designs combined with solvent engineering for optimization of enzymatic synthesis of L-ascorbyl palmitate were developed. First, the composition of the solvent for co-dissolving polar and apolar substrates was determined. The co-solvent mixture of tert-pentanol: DMSO at a ratio of 9:1 (v/v) and the optimal biocatalyst were obtained. Then, the Plackett-Burman design was implemented to screen the variables that significantly influence the conversion. The method of steepest ascent was used to approach the proximity of optimum. After determining the Plackett-Burman and steepest ascent designs, the optimum values were determined by central composite design under response surface methodology. The statistical analysis showed that the optimum reaction conditions (temperature 50°C, enzyme concentration 5.8 g/L, and substrate molar ratio 11:1, stirring rate 160 rpm, amount of molecular sieve 50 g/L, time 18 h) led to the maximum conversion (66.44%) and production concentration (20.63 g/L). A very satisfactory conversion (64.74%) and production concentration (20.13 g/L) could be achieved in short time (6 h).