Improving the production of E. coli beta-lactamase in Bacillus subtilis: the effect of glucose, pH and temperature on the production level.

Bacillus subtilis has been considered a promising host for the production of foreign proteins. However, proteases released by the host organism can often cause rapid breakdown of secreted heterologous proteins. Here we report that the addition of 6% glucose and 100 mM potassium phosphate to the growth medium significantly reduces the degradation of E. coli TEM beta-lactamase secreted from B. subtilis, when applying an expression system based on B. amyloliquefaciens alpha-amylase. The yield of beta-lactamase was increased 10-20-fold when compared to the yield in Luria medium. The promoter of B. amyloliquefaciens alpha-amylase gene is repressed by glucose. However, here we show that the repression does not take place in a multicopy plasmid, thus enabling our approach to efficiently reduce the protease action by catabolite repression. We have also studied the role of pH and temperature on the beta-lactamase production in laboratory scale bioreactors. Low temperature and low pH are both favorable for a high level beta-lactamase production by the high copy plasmid construction.