Optimization for concomitant production and partial purification of protease and lipase from Bacillus licheniformis 3C5 in aqueous two-phase system

Abstract

An organic solvent-, detergent-tolerant Bacillus licheniformis 3C5 has been recognized as protease-producing bacterium. Further tests revealed that this strain could also secrete proteolytic-resistant lipase with good stability in organic solvent and detergent and thus it is suitable for industrial co-application with protease. Further optimization studies for enhancing concomitant protease and lipase production were performed using response surface methodology (RSM). The maximum protease and lipase production was achieved using the optimized medium containing 0.86% glucose, 0.6% yeast extract, 0.25% NaCl and 2.5% olive oil (w/v), and led to an increase in yield by 2.20 and 12.57 folds. Finally, protease and lipase were partially purified by using an aqueous-two phase system (ATPS). The RSM was also applied to investigate the concentration effects of PEG6000, sodium citrate and KCl on the partition of both enzymes. It was found that protease was preferentially partitioned into PEG-rich top phase, whereas lipase was distributed to the interface. Accordingly, the best partitioning system was composed of 18.58% (w/w) PEG6000, 8.0% (w/w) sodium citrate and 4.0% (w/w) KCl. It provided 93.18% yield of protease and 92.59% yield of lipase with purification fold of 10.58 and 14.58, respectively.