Optimization of medium components and operating conditions for the production of solvent-tolerant lipase by Bacillus sphaericus MTCC 7542

Abstract

The production of lipase by Bacillus sphaericus MTCC 7542 growing on basal media with various carbon, nitrogen sources and environmental conditions was studied. Studies were undertaken to improve lipase production. Olive oil, Tween 80, rice bran oil, sunflower oil, soybean oil, palm oil and groundnut oil were tested as different lipid sources in this medium, with olive oil at 1% giving a lipolytic activity of 0.19 U/ml after 48 h, which was the highest yield obtained in this study. The effect of carbon source was studied by adding glucose, fructose, sucrose, lactose, starch and cellulose to a medium containing potassium nitrate and other minerals maintained as constant. The best yield of 0.20 U/ml after 48 h was obtained with the medium supplemented with 0.2% of glucose. The effect of nitrogen source was studied by adding peptone, yeast extract, tryptone, gelatin, casein, ammonium chloride, urea, ammonium sulphate, ammonium nitrate and ammonium acetate. The maximum yield of 0.21 U/ml after 48 h was obtained with the medium supplemented with yeast extract and ammonium chloride. Enzyme production was best at 7.5 pH, within a range tested from 6.5 to 8. The maximum enzyme was obtained at 35°C within a range tested from 25 to 40°C. These results are promising because this strain produces lipase in an inexpensive medium and we succeeded in increasing the lipolytic activity 3-fold over the initial values obtained with the non-optimized medium.

Key words: Bacillus sphaericus MTCC 7542, basal media, olive oil, lipolytic activity, ammonium chloride,mineral salts.