Metabolic Engineering of Bacillus

Microbial cultures usually produce a significantamount of acidic byproducts which can repress cellgrowth and product synthesis. Metabolic engineeringprovides a powerful approach to optimize the cellularactivities and improve product yields by geneticallymanipulating specific metabolic pathways. In thisstudy an inducible PYK (iPYK) mutant of B. subtiliswas constructed based on the outcome of metabolicmodeling. The results demonstrate that good cellgrowth rate and low acetate formation can be attainedat an appropriate PYK expression level. In Additionthe PYK mutation was explored as an efficient way toimprove the production of recombinant protein andvaluable metabolites such as folic acid. Acombination of PYK mutation and additional mutationsin the folic acid synthesis pathway resulted in an8-fold increase in folic acid production. Recombinantprotein was improved two-fold by the PYK mutation dueto low acetate formation and longer production timein the pyk mutant.