Researches On The Reaction Medium And Pilot-scale Process Of Producing (s)-ped With Stereoinversion Method By Candida Parapsilosis

(S)-1-phenyl-1, 2-ethanediol ((S)-PED), as one kind of aromatic chiral alcohols, is a versatile chiral building block for the synthesis of pharmaceuticals, agrochemicals, and fine chemicals. In this paper, the asymmetric synthesis of (S)-PED catalyzed by Candida parapsilosis CCTCCM203011 in aqueous phase was investigated. To scale up producing (S)-PED with bio-stereoinversion reaction, reaction system, biocatalyst fermentation, the preparation and refining of (S)-PED were studied which would establish the foundation for industrialization. Main conclusions are shown as follows:1) Aqueous two-phase system (ATPS) was constructed for improving stereoinversion on producing (S)-PED. Substrate concentration was enhanced from 15 g/L to 30 g/L after reaction 60 h with optimized ATPS, and optical purity and yield can remain 99.02% e.e. and 90% respectively. Simultaneously, cell morphological change was observed in this system to obstacle the further enhancement of substrate concentration, but can be reversibly changed after stereoinversion or cultivation in systems without PEG, which can be the foundation of multi-batch reaction.2) Preparing biocatalyst with pilot-scale was the premise of producing (S)-PED at pilot-scale. To solve the problem of lower pH and lower bio-stereoinversion ability, fermentation scale was gradually enlarged from 250 mL flask to 30 L tank and 150 L tank. Finally, the optical purity was >98% e.e. and yield of (S)-PED was >88% with the fermentation condition of 40 g/L glucose, 7 g/L yeast extract, 50 r/min agitation speed and 0.5 vvm ventilation volume in the 150 L bioreactor. Biocatalyst can be preserved for at least 21 days at 4°C and can bio-stereoinverse two batches that ensure the optical purity of (S)-PED was >95% e.e. which was the same as biocatalyst from 250 mL flask.3) Relatively matured process of resin/aqueous two-phase system, rather than the in studying process of ATPS, was applied for pilot-scale preparation (S)-PED. Based on the successful pilot-scale fermentation of biocatalyst, bio-stereoinversion reaction, which contained 25 g/L (R, S)-PED and 100 g/L biocatalyst with resin/aqueous two-phase system, was scaled up to 100 L in 50 L bioreactor, and after 48 h the optical purity and yield of product were 99% e.e. and 93%, respectively. Vacuum distillation was used as the main refining step compared with other methods, and the final yield was about 85%.