| Summary: | 碩士 === 國立海洋大學 === 食品科學系 === 89 === The dried bonito (Katsuobushi) had been placed at 25℃, RH 70-80% for molding. There were 2 strains of molds which having lipase activity have been isolated and named as strains S21 and S22. Under the microscope observation, it was shown that the strain S22 having a single conidiophore or branch synnemata which was brushlike. The conidia were green when cultured by agar plate. Suggesting that the strain was belonging to Penicillium spp. According to the entrusting determination of CCRC, the strain S22 had been identified as Penicillium citrinum.
In order to study the optimal culture conditions for producing lipase by Penicillium citrinum, the strain was grown in a medium consisting of 1% olive oil and 0.5% yeast extract at 30℃and 120 rpm shaking incubation for 5 days. The strain showed the maximal lipase activity after 5 days cultivation, and the addition of cupric sulfate, potassium chloride and zinc chloride were helpful for the strain to produce lipase. Some properties of the crude enzyme are as fellow: the optimal temperature is 45oC, and the enzyme showed optimum at pH 8.0. The substrate consisting of 5% (w/v) emulsifier and 50% (v/v) olive oil was the best substrate for lipase production. The enzyme was stable at pH 7.0-8.0 and it’s activity was remained at —20 and 4℃ for 2 months.
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