A glycerol-inducible thermostable lipase from Bacillus sp.: medium optimization by a Plackett-Burman design and by response surface methodology.

The production of a neutral lipase from a Bacillus sp. was improved tremendously (193-fold) following media optimization involving both the "one-at-a-time" and the statistical designing approaches. The present lipase was poorly induced by oils, instead its production was induced in the presence of sugars and sugar alcohols, mainly galactose, lactose, glycerol, and mannitol. A high inoculum density of 15% v/v (A550 = 0.8) led to maximum lipase production. Interestingly, the enzyme induction was growth independent, a property very different from most of the lipases investigated to date. The optimal composition of the growth medium to achieve maximum lipase production was determined to be as follows: NH4Cl, 35 g x L(-1); glycerol, 10 mL x L(-1); K2HPO4, 3 g x L(-1); KH2PO4, 1 g x L(-1); MgSO4.7H2O, 0.1 g x L(-1); glucose, 2 g x L(-1); MgCl2, 0.6 mmol x L(-1), with 15% inoculum density and an incubation period of 24 h. About 62 U x mL(-1) of enzyme production was achieved in the optimized medium.