Isolation, screening, and extraction the more efficient local yeast isolates for biosurfactant production

Abstract

Twelve samples of three spices of fruits (Kiwi, orange, and apple) and two spices of vegetables (Green pepper and cucumber) were collected from local shops and supermarkets to isolate the yeast using solid YEPG medium, twenty local yeast isolates were prepared from all samples, thereafter each isolate was tested for its ability to produce biosurfactant using liquid YEPG medium. Results have indicated that only three isolates had the ability to produce the biosurfactant at different abilities in growth medium depending on the emulsification index after 24 hr. They were tested for the production of extracellular biosurfactant only three isolates OS2, AS 9, and PS 14 were able to produce biosurfactant with emulsification index (E₂₄) against machine oil 36%, 47% and 28% respectively also was capable to spread oil by 12mm, 20mm and 9mm respectively but they didn't reduce YEPG medium surface tension significantly. The three isolates OS2, AS 9, and PS 14 were tested for intracellular biosurfactant, which gave the highest ability to emulsify both machine oil and crude oil, where the emulsification index (E₂₄) reached 46%, 80%, and 55% towards motor oil and 50%, 100%, and 62% towards crude oil for the three isolates, respectively. According to these results, the isolate AS 9 was regarded as the best producer for biosurfactant and identified this isolate as a Saccharomyces cerevisiae. Thereafter this biosurfactant was partially purified using cold ethanol and left to dry using a Rotary evaporator and then converted into a powder by using a Freeze dryer.