Statistical medium optimization and production of a hyperthermostable lipase from Burkholderia cepacia in a bioreactor

Abstract

Aim: Statistical medium optimization for maximum production of a hyperthermostable lipase from Burkholderia cepacia and its validation in a bioreactor. Methods and Results: Burkholderia cepacia was grown in shake flasks containing 1% glucose, 0.1% KH2PO4, 0.5% NH4Cl, 0.24% (NH4)2HPO4, 0.01% MgSO4.7H2O and 1% emulsified palm oil, at 45°C and pH 7.0, agitated at 250 rev min-1 with 6-h-old inoculum (2% v/v) for 20 h. A fourfold enhancement in lipase production (50 U ml-1) and an approximately three fold increase in specific activity (160 U mg-1) by B. cepacia was obtained in a 14 litre bioreactor within 15 h after statistical optimization following shake flask culture. The statistical model was obtained using face centred central composite design (FCCCD) with five variables: glucose, palm oil, incubation time, inoculum density and agitation. The model suggested no interactive effect of the five factors, although incubation period, inoculum and carbon concentration were the important variables. Conclusions: The maximum lipase production was 50 U ml-1, with specific activity 160 U mg-1 protein, in a 14 litre bioreactor after 15 h in a medium obtained after statistical optimization in shake flasks. Further, the model predicted reduction in time for lipase production with reduction in total carbon supply. Significance and Impact of the Study: Statistical optimization allows quick optimization of a large number of variables. It also provides a deep insight into the regulatory role of various parameters involved in enzyme production.