Chiang Mai Journal of Science

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The Bacillus stearothermophilus strains P1, TP404 and TP811 were cultivated in routine medium consisted of tryptone, yeast extract, base mixture, phosphate buffer pH 7.2 and olive oil in distilled water at 65° C in a shaking incubator at 200 rpm. It was found that B. stearothermophilus P1 could produce highest lipolytic activity of 3.54 U/ml at 30 h of cultivation. It was then cultivated in 4 different culture media included routine medium in the presence of octylphenoxy poly hydroxyethanol (Triton X-100) and polyoxyethylene sorbitan monooleate (Tween 80). The results showed that both detergents did not enhance lipase production but addition of Tween 80 into culture medium at concentration of 0.5% (v/v) could stabilize the enzyme activity. The bacterium was also cultivated in whey medium consisted of base mixture, whey and phosphate buffer with or without Tween 80. The cells could produce equal amount of lipase in routine medium. The results demonstrated that the bacterium could produce lipase in whey and Tween 80 do not facilitates the utilization of whey medium. The cloned of lipase genes from B. stearothermophilus P1 in E.coli DH5a using pUC 19 as an expression vector named pUC-P1 was also cultivated in Luria-Bertani (LB) medium with or without 0.5% (v/v) Tween 80 at 37° C which produced lipase 2 times higher than the native P1 cultivated in routine medium. The presence of Tween 80 in various culture medium of pUC-P1 could stabilize the enzyme activity in the cultivating medium but did not enhance lipase production.

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