| Summary: | 碩士 === 元智大學 === 生物科技暨生物資訊研究所 === 93 === Biosurfactants are amphiphilic molecules synthesized by a wide variety of microorganisms. Surfactin is a lipopeptide-type biosurfactant produced by various strain of Bacillus subtilis and is one of the most powerful biosurfactant so far known. This study aimed to identify better medium compositions in order to achieve more efficient production of surfactin from Bacillus subtilis CWS1, which is a mutant of Bacillus subtilis ATCC 21332. The establishment of an optimal medium associated with three major parts of medium components (namely, trace elements, nitrogen source and carbon source), which were examined individually for their effects on surfactin production. As for trace elements, the results show that Mg, K, Mn and Fe played important roles in surfactin production with complicated interactions among them. The maximum yield of surfactin via orthogonal array experimental design was 3.34 g/L. The production of surfactin was also evaluated by using different salts (NH4NO3、NH4Cl and (NH4)2HPO4) and the yield reached 2~3 g/L. Furthermore, surfactin concentration increased dramatically to almost 5 g/L by using OUCC-N1 as the nitrogen source. Among carbon sources examined, Bacillus subtilis CWS1 preferred utilizing carbohydrates to produce surfactin. This work shows that the best medium for surfactin production was MS medium supplemented with 16% sweet potato attaining approximately 1.4-fold higher surfactin yield than that of the original MS medium. However, combination of the three culture medium systems did not reveal the best yield of surfactin which only 3.2 g/L. In contrast, mineral salt medium (MS medium) containing 8 g/L OUCC-N1 and 16% sweet potato gave a maximum yield of 6 g/L, which is feasible for commercial-scale production.
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