Parameter Optimization Of Extractive Microbial Transformation In Nonionic Surfactant Micellar Aqueous Solution

L-phenylacetylcarbinol (L-PAC), an important organic intermediate, can be used as precursor to synthesize L-ephedrine and D-pseudoephedrine in pharmacy industry. It is also applied for amphetamine, aniline and amphetamine synthesis.Extractive microbial transformation of L-PAC in direct nonionic surfactant micelle aqueous solution was carried out as the good biocompatibility of Saccharomyces cerevisiae in Triton X-100 micelle aqueous solution. The solubilization of organic compounds in the nonionic surfactant micelles prevents the inhibition of organic compounds to the microbial cells in the nonionic surfactant micelle aqueous solution and the microbial transformation with a high substrate concentration was maintained. At the same time, the utilization of nonionic surfactant Triton X-100 with high Hydrophilic-Lipophilic Balance (HLB) value in extractive microbial transformation makes it potential for stripping of the product from the nonionic surfactant and recycling of the nonionic surfactant by Winsor I microemulsion extraction.The basic extractive microbial transformation conditions, including pH, substrate benzaldehyde concentration, nonionic surfactant Triton X-100 concentration, glucose concentration, acetaldehyde concentration, cell concentration, filled volume(dissolved oxygen), nitrogen source, and transformation time, was evaluated by the single-factor-experiment method. The corresponding optimal conditions were pH 5.2, benzaldehyde concentration 0.9% (mL/mL), Triton X-100 concentration 7.8% (g/mL), glucose concentration 3% (g/mL), acetaldehyde concentration 0.6% (mL/mL), cell concentration 12% (g/mL), filled volume (dissolved oxygen) 20 mL/50 mL, the transformation time 6th hours, and without any nitrogen source. As the strong interaction between benzaldehyde and nonionic surfactant Triton X-100 in the extractive microbial transformation process, a response surface method with Box-Behnken design was applied to further analysis the interactions among benzaldehyde, Triton X-100 and glucose. Based on the results of the above single-factor-experiment, an optimal combination with benzaldehyde 1.2 mL/100 mL, Triton X-100 15 g/100 mL and glucose 2.76 g/100 mL was obtained. Its maximum response value of L-PAC concentration 27.61 mM was experimentally confirmed. A high product L-PAC concentration 50.5 mM by a discrete fed-batch process was also presented.