Isolation, Identification and Optimization of the Growth Conditions for Lipase Production by Bacillus sp.

BACKGROUND AND OBJECTIVESEnzymes, which have important metabolic functions for cellular structures, have entered daily and economic life to be used for various purposes. Lipases are enzymes that break down the glycerol esters of fatty acids. They are a physiologically and commercially important group of enzymes as their use increases rapidly and steadily for various biotechnological applications. The objective of this study was to isolation, identification and optimization of the growth conditions for lipase production by soil Bacillus sp.MATERIALS AND METHODSThe isolation of bacteria producing lipase from soil was conducted using a TBA medium. The identification of bacterial isolates was achieved through a combination of morphological, biochemical, and ۱۶S rRNA methods. Enzyme activity was assessed by titrimetric analysis. Then, nutritional and physical parameters were optimized for production of lipase by Bacillus sp. Also, effect of carbon sources (coconut oil, corn oil, glucose, maltose, sucrose, starch, soybean oil, sunflower oil, and olive oil), organic and inorganic nitrogen sources (yeast extract, corn step liquor, peptone, tryptone, ammonium phosphate, ammonium nitrate and ammonium sulfate), different metal ions (MnSO۴, FeSO۴, LiSO۴, BaCl۲, KCl, NaCl, CaCl۲, CuSO۴), different temperatures (۳۵-۶۰ °C), pH ranges (۴-۹), inoculum amounts (۵-۱۰%) on enzyme production were studied.RESULTS AND DISCUSSIONOut of the ۵۶ enzyme-producing isolates screened on TBA medium, ۷ was identified as excellent lipase producer. Among these, a bacterium that produced the enzyme with high activity were selected for the next stage. Analysis of the ۱۶S rRNA sequences of these isolates revealed a remarkable ۹۹% similarity with Bacillus cereus. Results showed that sucrose and ammonium phosphate are the optimal sources of carbon and nitrogen, respectively. CaCl۲ was found to be the best metal source. Optimal lipase activity was achieved at a temperature of ۴۵°C, a pH of ۷ and following a ۷% of inoculum amounts.CONCLUSIONThe current research explored our local environments, searching for bacterial isolates that produce lipase. It suggested that Bacillus cereus isolated from the soil had the potentiality for lipase production and can be used in industry.

کلیدواژه ها:

Lipase ، Bacillus cereus ، Growth conditions ، Soil