Effect Of Organic Nitrogen On Heterogenous Protein Expression And Cell Growth Of Escherichia Coli In Glycerol-containing Medium

The effects of organic nitrogen and dissolved oxygen on heterogenous protein (purine nucleoside phosphorylase, PNPase) expression by E. coli in glycerol-containing medium were investigated, and the mechanisms of organic nitrogen on acceleration effect of cell growth of E. coli were also carried out in this study. In the 5 L fermentor culture, peptone contained in culture medium had very important impact on expression of exogenous protein, among the five tested peptone, peptone I showed highest production of exogenous protein, the content of heterogenous protein, the activity of enzyme and the specific activity of enzyme were 41.9%, 440 U and 3.8 U/mg. The highest production of exogenous protein was also obtained by controlling appropriate level of dissolved oxygen, the optimal level of dissolved oxygen is 10-30% of saturation oxygen concentration, which meet the reqiurement of microorganisms, maintaining an ideal growth state and aviod generating structural destruction to expressed protein. Furthermore, The effects of organic nitrogen on cell growth of E. coli were observed. In the flask culture, Acceleration effect of amino acid supplementation on growth of E. coli in glycerol-containing minimal medium was observed. Among the tested 12 amino acids, Arg and Ser (0.35 mM) showed the highest efficiency, increasing cell growth by 63% and 53%, respectively compared to control cells. Our results show acceleration effect of amino acid supplementation on growth was achieved by promoting glycerol utilization not achieved by using amino acids as carbon source or nitrogen source. This acceleration effect probably only exists in non-phosphoenolpyruvate carbohydrate phosphotransferasesystem (non-PTS) sugar...