Improving production of thermostable and fluorescent holo-β-allophycocyanin by metabolically engineered Escherichia coli using response surface methodology.

A stable fluorescent holo-β-allophycocyanin (holo-ApcB) was produced by metabolically engineered Escherichia coli. The E. coli cells harbored two plasmids for expression of five genes that were involved in the holo-ApcB production. Response surface methodology was employed to investigate the individual and interactive effects of four variables, i.e., initial pH of culture medium, IPTG concentration, post-induction temperature, and induction start time, on holo-ApcB production by E. coli. The experimental results showed that the IPTG concentration, postinduction temperature, and induction start time had significant individual effects on holo-ApcB production. A significant interactive effect was also found between the initial pH of culture and induction start time. The maximum holo-ApcB production of 45.3 mg/L was predicted under the following optimized culture conditions: a postinduction temperature of 28.4°C, initial pH of culture of 7.3, IPTG concentration of 1.1 mM, and postinduction time of 66 min. Holo-ApcB production under the optimized culture conditions increased 5.8-fold, compared with that under the nonoptimized conditions. Response surface methodology proved to be a valuable tool for optimization of holo-ApcB production by metabolically engineered E. coli.