Optimization of physico-chemical parameters for biosurfactant production by yeast
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Date
2017
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CCSHAU
Abstract
Commercial production of biosurfactant, a surface-active compound produced by
microorganisms such as bacteria, yeast and fungi, is restricted due to increased cost of production
which could be lowered down by optimization of production process using high yielding strains. The
present investigation was designed to optimize various physical and chemical parameters of
biosurfactant production monitored in terms of oil displacement and E24 index, by four promising
isolates, YK20, YK21, YK22 and YK32. Among carbon sources, olive oil at 8%(v/v) concentration
was optimized as it gave maximum oil displacement of 7.5cm in case of isolate YK32 followed by
6.6cm in case of isolate YK20. Diesel being complex hydrocarbon source was not utilized easily and
showed poor biosurfactant production, however it was maximum supported by YK22 which gave
maximum oil displacement of 4.5cm after 5 days of incubation. Yeast extract at 1.5%(w/v)
concentration yielded maximum biosurfactant as evident from maximum oil displacement of 8.1cm
followed by 7.3cm along with an emulsification index of 52.6% and 50.2% in case of isolates YK32
and YK20, respectively. Yeast extract showed most encouraging results with isolate YK22 as its
supplementation, approximately doubled the biosurfactant production in first 24h from 1.2-1.9cm to
3.0-3.1cm at different concentrations Sodium chloride concentration at the rate of 3%(w/v) was
selected for further studies as it supported oil displacement of 8.8 and 8.1cm given by isolates YK32
and YK20, respectively. Any increased concentration above this level, negatively influenced the
biosurfactant production. Biosurfactant production was observed maximum at 30°C as monitored in
terms of oil displacement of 8.8cm in case of isolate YK32 and it decreased marginally as the
temperature was shifted to either 35°C (5.2cm) or 25°C (7.6cm). An increased temperature to 40°C,
however, decreased oil displacement, significantly to 2.5cm. Biosurfactant production appeared to be
sensitive to varying pH as evident from an emulsification index as high as 67.3% at pH 6.0 in case of
isolate YK32 as compared to 60.2%, 60.1% and 52.4% at pH 5.0, 5.5 and 7.0, respectively. Maximum
biomass production, 10.3g/L, was observed at pH 6 in isolate YK32 while a minimum biomass, 6.3g/L
was attained at pH 7 in case of isolate YK21. Elimination of shaking at the rate of 150rpm reduced the
emulsification index from 63.8% to 30.3%, 58.8% to 34.1% and 60.2% to 30.6%, respectively in case
of isolates YK20, YK21 and YK22 after 5 days of incubation.
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