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

Abstract

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 β-lactamase secreted from B. subtilis, when applying an expression system based on B. amyloliquefaciens α-amylase. The yield of β-lactamase was increased 10–20-fold when compared to the yield in Luria medium. The promoter of B. amyloliquefaciens α-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 β-lactamase production in laboratory scale bioreactors. Low temperature and low pH are both favorable for a high level β-lactamase production by the high copy plasmid construction.