Abstract:
This study aimed to improve the biosurfactant yield of Candida mucifera NJP25 and optimization of the culture medium and culture conditions using one factor at a time (OFAT) and response surface methodology (RSM). The study considered the effects of carbon and nitrogen source, C:N ratio, pH and temperature. When studying one factor at a time that consisted of 4.0% sucrose (w/v), C:N ratio 20:1, pH 6.5 within a shake flask at 200 rpm and incubated at 30°C for 9 days, the surface tension of culture medium was decreased from 53.2 mN/m to 35.5 mN/m and oil displacement in medium 0.62 cm2 and the biosurfactant yield of 0.26 g/L. The results from Box-Behnken design showed that the optimized medium containing 7.0% sucrose (w/v), C:N ratio (NaNO3) 15:1, pH 6.5 at 30°C, could increase the biosurfactant yield to 1.64 g/L. The biosurfactant showed a critical micelle concentration (CMC) value of 27.48 mg/ml at the surface tension of 34.81 mN/m and emulsification activity with vegetable oils. The study of stability test, it remained unchanged properties of the biosurfactant within a wide range of environmental condition such as pH (2-10), NaCl concentration (2-10 %) and temperature (4-100ºC). A partially purified biosurfactant fraction with preparation TLC and HPLC displayed both major biosurfactants, F2-1 and F2-4, showed high biosurfactant activity by oil displacement assay and further analyzed via LC-MS. Their molecular mass were 375 474 490 and 506. There were molecular mass different substance from sophorolipid found in other yeasts.