Isolation, screening, and characterization of yeasts for biosurfactant production using waste cooking oil as substrate
2002
Yabes, M.P.
One hundred sixty-one yeasts isolated from copra, soil, water and wastewater samples from various food-and oil-processing plants in Laguna and Quezon [Philippines] were screened for lipid degradation. Preliminary screening for lipolytic activity was done based on the abilities of the isolates to hydrolyze Tween 80. Forty-three yeast isolates positive for hydrolysis of Tween 80 were also capable of degrading different plant oils and animal fats but at varying rates. Corn oil, olive oil, rapeseed oil, and pork fat were among the easiest substrates to degrade, being hydrolyzed within 2-3 days. Most isolates showed only weak hydrolysis of coconut oil, soy bean oil, and sunflower oil. Three lipolytic yeast isolates designated as Y36, Y42, and Y49 exhibited high lipase and emulsifying activities when grown with waste cooking oil as substrate. The biosurfactants produced by these isolates were more effective at stabilizing oil-in-water emulsions rather than reducing surface tension. Analysis of the partially purified high-molecular weight bioemulsifier from isolate Y42 showed that it was composed of approximately 73% carbohydrates and 22% protein. On the other hand, the emulsifier produced by Y49 was made up of approximately 52% protein and 43% sugar, while that of Y36 was composed primarily of protein (approximately 91%). Based on cultural, morphological, and biochemical tests, isolate Y49 was identified as Pichia guilliermondii. Isolates Y36 and Y42 also belonged to the genus Pichia, but further tests should be done to determine their species. The results showed that bioemulsifier production by yeasts using waste cooking oil as substrate can be an alternative strategy for management of this type of waste
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