Maximum Yield of Foreign Lipase in Escherichia coli HB101 Limited by Duration of Protein Expression

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When a microbial lipase was overexpressed in Escherichia coli HB101,the expression kinetics as represented by the expression rate, duration, and maximum yield of lipase were studied. Lipase synthesis, controlled by the tac promoter, continued for about 4 h after IPTG induction. The duration of the expression phase was similar, irrespective to expression rate and yield, which were manipulated by using α-methyl glucose (α-MG), a competitive inhibitor of glucose. By measuring the specific oxygen uptake rate, specific CO_2 evolution rate, specific glucose uptake rate, intracelullar protease level and the acetate concentration in the culture, the limited duration of the expression phase was found to be caused by metabolic stress aristing from the rapid and massive production of the foreign protein under the strong promoter. Neither the total cell number nor the number of living cells increased substantially after induction, whereas the optical density of the culture gradually increased. The duration of the expression phase was reduced to less than 2 h by the addition of menadione, a redox cycling agent, seemingly due to an acceleration of the energetic flow of the host cells after induction. In contrast, the duration of the expression phase was extended to 8 h in the glucose-starved condition, althrough the maximum expression yield was much lower than that in the glucose-surplus condition. Therefore, it was suggested that the expression rate after induction determined the maximum expression yield of the foreign lipase gene in E. coli HB101 because of the restrained capacity of foreign protein production.
社団法人日本生物工学会の論文
1995-03-25

Maximum Yield of Foreign Lipase in Escherichia coli HB101 Limited by Duration of Protein Expression

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