European Journal of Biotechnology and Bioscience  ~ 43 ~  Volume: 3, Issue: 6, 43-48 June 2015 www.biosciencejournals.com ISSN: 2321-9122 Impact Factor: 3.742 Zehra Burcu Bakir Department of Biology, Faculty of Science and Arts, Adnan Menderes University, 09010 Aydın, Turkey Kubilay Metin Department of Biology, Faculty of Science and Arts, Adnan Menderes University, 09010 Aydın, Turkey Correspondence: Zehra Burcu Bakir Department of Biology, Faculty of Science and Arts, Adnan Menderes University, 09010 Aydın, Turkey Screening for industrially important enzymes from thermophilic bacteria; selection of lipase-producing microorganisms and optimization of culture conditions Zehra Burcu Bakir, Kubilay Metin Abstract In this study, 201 thermophilic bacteria that were isolated from natural hot springs in Aydin/Turkey and registered in Adnan Menderes University Department of Biology culture stocks were used. It was determined that 43 of these bacteria exhibited lipolytic activity and 22 of them exhibited lipase activity. These 22 lipase positive isolates were grown in LB broth medium and the quantitative lipase activities were determined. HBB 134 was chosen as the best lipase producing isolate with the activity of 19.925 U/mL. According to 16S rRNA sequences, it was found that the isolate showed maximum similarity (% 99) with Anoxybacillus flavithermus. The best enzyme production from HBB 134 was determined in medium including 0.5% olive oil as carbon source and 0.5% pepton as nitrogen source, pH 6.50 and 45 °C. When the isolate HBB 134 was grown in optimum culture conditions it was determined that production of the lipase started at the beginning of the logarithmic growth phase and it reached maximum level in the middle (12 hour) of the logarithmic phase. It was determined that most of the enzyme activity was intracellular. Keywords: Screening, Lipase production, Anoxybacillus flavithermus, thermophilic, culture conditions. Introduction Microbes and their enzymes are used in a wide range of biotechnological applications such as, detergent, fine chemicals, pharmaceutical, bioremediation, food, leather, paper and textile industry. The most important enzymes for industry are lipases, carboxylesterases, cellulases, xylanases, pectinases, amylases and proteases. Lipases (triacylglycerol acylhydrolase; EC 3.1.1.3) are enzymes that catalyze the hydrolysis of mono-, di- and triacylglycerides to glycerol and free fatty acids at an oil-water interface. Lipases due to their application in a wide range of industrial applications have emerged as key enzymes in rapidly growing biotechnology. Lipases are widely used in biocatalysis due to their ability to catalyze not only the hydrolysis of triacylglycerides in aqueous solutions, but also regio-, enantio- and stereoselective reactions in organic media [1] . Lipases are produced by plants, animals and microorganisms. However, microbial lipases including bacteria, fungi and yeast are also more stable than their corresponding plant and animal sourced enzymes and their production is more suitable, economical and safe [2] . Lipase-producing microorganisms are mostly found in diverse habitats such as industrial wastes, vegetable oil processing factories, dairies, soil contaminated with oil, oilseeds, decaying food, compost heaps and hot springs [3] . Lipases produced from different microbial sources have different properties such as pH and temperature stabilities and substrate specificity. Enzymes from thermophilic organisms are more stable than similar enzymes from mesophilic organisms therefore they are more useful for biotechnological applications [4] . Thermostable enzymes are important to have higher reaction rate at higher operation temperature. Substrate solubility can increase at higher temperatures and thereby avoid environmental contamination [5] . In this case, screening of new thermophilic microbial lipases has special importance in finding novel lipases that have suitable properties for different industrial aplications. Lipase production is influenced by the type and the concentration of the carbon and the nitrogen sources, the culture pH, the growth temperature, and the dissolved oxygen concentration [6] . Furthermore, the presence of activators, stimulators, inhibitors and the surfactants, in addition to the amount and the source of inoculum can also influence the production of lipases. There are many reports about the optimum culture conditions and the nutritional requirements for lipase production. [7, 8, 9, 10, 11, 12] . However, none of the reports have been regarding Anoxybacillus. The thermophilic bacterium Anoxybacillus flavithermus HBB 134 used in this study was isolated from a hot spring in Alangüllü/Aydın (50°C). Various culture growth