Aspergillus sp. (MTCC 5436), isolated from contaminated clarified butter was used as a whole cell catalyst for transesterification of oils from different sources. The strain was observed to be tolerant and grow in 90% oil as carbon source. Oils of Jathropa, karanj and spent cottonseed were used as carbon sources in the study. The product, alkyl ester, was characterized and quantified using (1) H-NMR. The strain was observed to facilitate transesterification in an oil:minimal medium with the ratio of 70:30 resulting in a 98% conversion of oil to ethyl esters within 48 h at 28 °C and 120 rpm. The physico-chemical characteristics of the ethyl ester (>98%) at 70% oil as carbon source were similar to the standards specified for biodiesel as per standards of American Society for Testing and Materials (ASTM) and Bureau of Indian Standards (BIS), India.
Extracellular lipase production by Aspergillus sp. (RBD-01) was monitored by modulating pH of the growth medium, ambient temperature for growth, source of nitrogen and percentage of carbon (virgin cottonseed oil). This strain was observed to be viable and produces lipase even up to 50% oil as a main carbon source. Maximum lipase activity of 21.8 U/ml was obtained with 50% (v/v) oil acting as the main carbon source and peptone (0.5% w/v) as nitrogen source. The optimum pH and temperature for enzymatic activity were observed to be 7.5 and 35 degrees C, respectively. The observations are of significance due to limited reports on use of 50% of oil as the main carbon source while obtaining significant lipase activity of 21.8 U/ml.
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