Application Of Immobilization C.Valida In NaCS-PDMDAAC Microcapsules

As a new cell microencapsulation system, sodium cellulose sulfate (NaCS)-poly(dimethyl-dially-ammonium chloride) (PDMDAAC) microcapsule has been attracting a wide range of attention in the field of biotechnology. It owns the advantages of stable mechanical strength and properties, as well as good biocompatibility and easy preparation, etc. It continues to hold significant promises for biotechnology and medicine. In this paper, the C. valida immobilized in the microcapsules were used in the lipase production and the asymmetric reduction reaction of acetophenone to (R)-1-phenylethanol.The fermentation conditions were optimized to gain the maximum yield of lipase in submerged culture of C. valida. The conformable carbon and nitrogen suited to the growth and the lipase production were conformed, and then the initial concentrations of glucose and olive oil were further optimized. The influence of external factors, such as shaking speed, initial pH and temperature were also optimized. The optimized conditions allowed the lipase production to increase to 10.95U/ml.The C. valida immobilized in the microcapsules were used to product the lipase. The maximum lipase activity reached to 17.2U/ml for 80 hours' batched cultivation and the top cell mass was 26.2g/L at 92h, which was 4 times more than that in free cell culture. The yeast cells were further immobilized in the macroporous microcapsules, which allowed the lipase to diffuse from the capsules to culture medium. Because of the separation of the lipase and cells, the advance was more evident. The time-space yield of lipase was 81% more than that in submerged culture and 7.5 times more if calculated by the volume of microcapsules.The properties of the asymmetric reduction reaction of ACP were investigated, including the effects of temperature, pH, reaction time, substrate concentration, amount of yeast cells on the conversion and stereselectivity. The optimized reaction conditions allowed the conversion to as high as 99%, and the e.e. of R-PEA to be 90.7%. In addition, the effects of the cell culture condition and heating pretreatment were studied.The diffusion of ACP and PEA in the membrane of capsules was investigated, and then, the C. valida was immobilized in the microcapsules to do the asymmetric reduction reaction. The effects of the volume ratio of the capsules and PBS and the reaction time on the reduction of ACP were studied. The influences of glucose concentration, substrate concentration and cell culture condition were distinct on the batched reduction reaction. Finally, by controlling the substrate concentration and cell culture condition at the same time, the stereselectivity was changed from R-form to S-form.