Production Of L-Citrulline By Polyurethane Immobilized Streptococcus Faecalis Cells

L-citrulline is a non-protein amino acids, playing an important role in urea cycle. In this paper, the continuous process of transforming L-citrulline through immobilized microbial cells in packed bed reactor and repeated batch fermented was studied, aiming at establishing a set of low-cost, easy-operation, high-quality L-citrulline production systems in laboratory and laying the foundation for industrial production of L-citrulline in the future.This paper investigates the feasibility of using polyurethane immobilized Streptococcus faecalis. Experiment shows the dry weight of immobilized cell can reach 0.632g·g-1 with good effect after repeated washing, and confirms that Streptococcus faecalis cells and the vector of polyurethane have good biocompatibility.A series of experiments have been designed to further investigate immobilized factor of influence finding that its maximum adsorption capacity can be reached after 52h when volume of addition of polyurethane is 1.0g, size is 5×5x5mm, pH of culture medium is 7.0, shaker temperature is 35℃, rotate speed is 150r·min-1. Meanwhile, the optimal conditions of immobilized cells for preparation L-citrulline in the shaker are identified that the output of L-citrulline can be up to 53g·L-1 by 36h transformation at 35℃,50mL/250mL shake flask liquid volume, adding 0.6g immobilized cells, 100g·L-1 L-arginine as substrate, CTAB 0.3g·L-1 surfactant, initial pH 7.0, rotate speed 100r·min-1. The immobilized cells can be reused five batches and greatly shortened the transform time.The experiment also investigates the process of preparation for L-citrulline by immobilized cell in the packed bed reactor:at 35℃in thermostatic water bath, a reaction columnφ40×300 in size containing 26g immobilized cells, with a reaction solution containing 100g·L-1 of L-citrulline added at a flow rate of 40mL·h-1, 0.3mol·L-1 acetic acid buffer solution, 0.3g·L-1 surfactant CTAB, adjusted pH 7.0, the output of L-citrulline basically remain at 65g·L-1 and the immobilized cell can be successively used 15 times in packed bed reactor.Adopting Fluorescence quenching and ultraviolet absorption subtraction to study the interaction mechanism at different PH between L-citrulline and bovine serum albumin(BSA). Meanwhile, using Stern-Volmer equation to have variety of parameters.