Production Of (R)-Mandelic Acid By Asymmetric Reduction With Saccharomyces Ellipsoideus GIM2.105

Optical mandelic acid is a versatile chiral synthon used for the synthesis of various pharmaceuticals, and the applications of optical mandelic acid have grown markedly in recent years and are likely to expand in the coming years. Preparation of optically pure (R)-MA by biocatalyst has an advantage of mild reaction conditions, high stereoselectivity,high regioselectivity and high chemical selectivity. In this paper, the asymmetric synthesis of (R)-MA catalyzed by Saccharomyces ellipsoideus GIM2.105 in aqueous phase was investigated. For the aim of laying a foundation to prepare (R)-MA on industrial scale, the initial reaction substrate concentration, reusing of biocatalyst, extracting and purification of (R)-MA were studied.Study on the medium and fermentation condition of Saccharomyces ellipsoideus GIM 2.105.Defining the composition of medium: glucose 4%, yeast 0.3%, (NH4)2HPO4 1.3%, KH2PO4 0.658%, NaCl 0.012%, MgSO4·7H2O 0.05%, ZnSO4·7H2O 0.006%, MnSO4·4H2O 0.0038%. The effects of dissolved oxygen (DO) concentration and fermentation time on the culture of S. ellipsoideus in a 7L stirred fermentor were also investigated, the best fermentation condition has been confirmed, air flow rate was controlled at 4 L/min, the agitation rate and culture time were not less than 200 r/min and 24 h. In this situation, the yield increase from 40% to 59%, the microbic biomass could reach 28 g/L more than 15 g/L originally.The influence of various factors affecting the transformation process was investigated. The yield and e.e. value of reaction reached 70% and 99% at each one of 10 continuous batches under the following conditions: pH 6.5, 35°C, cellmass of 120g/L and substrate concentration of 10g/L,In the pilot-scale experiment on a 7 L of bioreactor, the good result with the yield of 81% was also obtained. Three continuous batches in the 7 L bioreactor were investigated, all of the yield could reach 80%, and e.e. value could reach more than 99%. Our research results could provide the theoretical and practice foundation for the industrial production of (R)-mandelic acid.The extraction and refinement of (R)-Mandelic acid was studied. From six kinds of resins, D303 resin was selected to adsorb (R)-MA. Benzene was selected as a suitable solvent for recrystallization of products. 2 L solution containing (R)-MA was adsorbed by the resin column with a flow rate of 1 BV/h, desorbed by 2 BV ethyl acetate, decolored by 3 % (mass concentration) active carbon by 80 min and recrystallized with about 200 mL benzene. When (R)-MA was extracted and purified under this condition, the total yield of (R)-MA was 75.6% with the mass fraction of 96.5% and optical purity of 99 %.