Biodiesel production from a novel Halotolerant Oleaginous Yeast

Biodiesel is an attractive substitute for petrodiesel due to its sustainability and environmental friendliness. Currently, for commercial biodiesel production bio-lipids extracted from edible vegetable oils are employed but... [ view full abstract ]

Biodiesel is an attractive substitute for petrodiesel due to its sustainability and environmental friendliness. Currently, for commercial biodiesel production bio-lipids extracted from edible vegetable oils are employed but are not sustainable. As an alternate microbial diesel particularly from oleaginous yeasts is an attractive solution as it offers features like high growth rate, high oil productivity on wide variety of substrates and can be produced in small land space. In the present study, soil samples having detritus matter were collected from IIT Madras campus, and Pichavaram mangrove. Samples were enriched in high C/N ratio (40), and chloramphenicol containing media to select yeast strains. Forty yeast strains were isolated and tested for oleogenicity, by growing in C/N ratio 75 medium. Total lipids accumulated after 96h of growth were estimated by primary screening using Sulpho phospho vanillin assay. Secondary screening was done by gravimetric estimation using chloroform-methanol extraction, 35 strains had total fatty acid content (TFA) below 25%, four strains had TFA between 25-35%  and one isolate OE21 accumulated carotenoids and lipids up to 50% of dry cell weight. Organism producing carotenoids are advantageous as carotenoids render oxidative stability to biodiesel. The isolate grew in sea water exhibiting halotolerance, a property useful for large scale cultivation. Therefore, isolate OE21 appears to have potential for large scale production even though there are yeasts producing over 60-70% lipids. FAME (Fatty acid methyl ester) profile of OE21 was determined using GCMS (Gas chromatography- Mass spectrometry) obtained by direct transesterification of the lyophilized cells. From this FAME profile the five essential  physical  properties of biodiesel were predicted using empirical equations reported by Luis et. al. 2012. A high Cetane number (66.53), low kinmatic viscosity (4.57mm³/s), low density (0.87g/cm³), higher heating value (39.80 MJ/kg) and Iodine Value (53.60 mg I₂/100g) were obtained and were found to cohere to ASTM 6751-08a standard recommendations. Results suggested that lipids from OE21 is of suitable quality for biodiesel production.