Studies On L-Glutamine Synthesis By Enzyme Method And Extraction

L-glutamine(L-Gln), one of important amino acids to construct protein, existinguniversally in human body, is an important conditionally necessary amino acid. L-Gln plays akey role in life, which has important effect on metabolism of muscle, cleavage and growth ofcell, rehabilitation of tissue wounded and neutralization of toxin in body. So, L-Gln is appliedwidely for nutrition supply, resistance tiredness, rehabilitation of gastric and enteric function,enhancement organ immunity and so on,and its market demand is going up increasingly. Atpresent, L-Gln is produced mainly by fermentation, and research on L-glutamine productionby the enzyme method was reported occasionally. In this paper, the foundation of the energycoupling system producing L-Gln by L-glutamine synthetase(GS) and highly efficient methodto produce L-Gln and to extract L-Gln from enzyme broth were built.Firstly, L-Gln produced by GS coupling with yeast alcoholic fermentation was studied. Itis determined that the airflow dry is the best method of the permeable treatment to yeast andAngel yeast is optimum strain comparing to the others. The influence of ATP, AMP, NAD,Mg²⁺, Mn²⁺ on the energy coupleing system was researched. The results showed that theoptimum concentration of Mg²⁺,Mn²⁺ both were 15mM and the optimum concentration forstart-up ATP was 5mM.Secondly, the effect of substrate of GS and yeast on the conversion of L-Gln in thecoupling system was studied and found that glutamate(Glu) affected mostly the conversion ofL-Gln through Orthogonal experiment and analyst. Under the optimum condition of reactive factor, theyield of L-Gln is 17.8g/L and the conversion rate is 71.2%. To get higher yield of L-Gln, feed-batch ofglucose and glutamate was determined. and the final yield of L-Gln is 33.8g/L and the conversion rateis67.6%.Finally, using Cl-resin 201×4 according to the distributional characters of Gln and Gluin the solution to separate L-gln was studied. In the optimum condition, the final recovery rateand the content of L-Gln is 66.6% and 97.2% respectively and the removal rate of Glu is 95%.