초록
Aspartase gene (aspA) from Aeromonas media NFB-5 was cloned and expressed in Escherichia coli BL21 using pET21b(+) expression vector. Maximum production of aspartase was obtained at shake-flask after 5h of IPTG (1.5mM) induction at 37<SUP>o</SUP>C and by supplementing the media with KH<SUB>2</SUB>PO<SUB>4</SUB> (0.3%, w/v) and K<SUB>2</SUB>HPO<SUB>4</SUB> (0.3%, w/v). Further production was investigated at a laboratory scale stirred tank reactor using response surface methodology (RSM). Agitation (130-270rpm), aeration (0.30-1.70vvm) and IPTG induction time (3-7h) was optimized. Optimal levels of agitation (250rpm), aeration (1.25vvm) and induction time (6h) were determined by statistical analysis of the experimental data. More than 7-fold increase in recombinant aspartase (1234U/g wet weight) was observed than the parent strain (172U/g wet wt). Homogenized immobilized permeabilized recombinant cells (566mg/g wet cells) produced more l-aspartic acid as compared to permeabilized recombinant free cells (154mg/g wet cells).