Study On High Cell Density Culture Of Escherichia Coli For Aminotransferase Production

The L-phenylalanine(L-Phe) is one of eight kinds of amino acid necessary to human, and has higher application value in food and medicine industries. In the enzymatic preparation of L-Phe, aminotransferase as a key enzyme for the aminotransformation, could make phenylpyruvate to accept the amidogen from L-aspartic acid. In this paper, under the precondition of ensuring the higher yield of L-Phe, high cell density culture of Escherichia coli(E. coli) for aminotransferase production was studied.Firstly, after a chemically defined medium was established, the single-omission technique was employed to investigate the effects of"18 kinds of amino acid, 11 kinds of vitamin, 8 kinds of trace element, 4 kinds of purine and pyrimidine"on the fermentation of E. coli for aminotransferase production. Secondly, fermentation condition was optimized in shaking flask. Finally, fed-batch culture of the strain in 5L fermentor was studied. Effects of feeding time of carbon source, feeding nitrogen source, feeding with pH control and feeding nutritional factors on E. coli fermentation were investigated to determine the optimal culture condition.Main conclusions of this thesis were as follows:1) Study on nutritional requirements for E. coli growth and aminotransferase production: In every nutritional factors, L-methionine was the vital compound for both growth of E. coli and production of aminotransferase. L-valine, L-isoleucine and L-glutamic acid was sufficiently useful for growth of the strain and preparation of the enzyme respectively.2) Study on optimization of E. coli fermentation for aminotransferase production in shaking flask:Optimal inoculation time and inoculation amount was 14h and 3% respectively. Optimal initial glucose concentration was 10g/L. Corn steep liquor(C.S.L.) and peptone(Pep.) were selected as organic nitrogen source for E. coli fermentation. By...