Aditi Pant

Palm oil mill effluent treatment by a tropical marine yeast

Palm oil mill effluent (POME), from a factory site in India contained about 250,000 mg l(-1) chemical oxygen demand (COD), 11,000 mg l(-1) biochemical oxygen demand, 65 mg l(-1) total dissolved solids and 9000 mg l(-1) of chloroform-soluble material. Treatment of this effluent using Yarrowia lipolytica NCIM 3589, a marine hydrocarbon-degrading yeast isolated from Mumbai, India, gave a COD reduction of about 95% with a retention time of two days. Treatment with a chemical coagulant further reduced the COD and a consortium developed from garden soil clarified the effluent and adjusted the pH to between 6 and 7. The complete treatment reduced the COD content to 1500 mg l(-1) which is a 99% reduction from the original.

Hydrocarbon degraders from tropical marine environments

Analysis of 20 samples of marine mud and water around Mumbai resulted in the isolation of 17 bacteria and yeasts all of which were able to degrade more than 10% of the supplied crude oil. The yeasts strains were important degraders of the aliphatic fraction of crude. All the isolated yeasts belonged to the genus Candida. Using biochemical tests these were identified as Candida parapsilosis, C. albicans, C. guilliermondii, Yarrowia lipolytica, C. tropicalis and C. intermedia. Y. lipolytica was the best degrader utilizing 78% of the aliphatic fraction of Bombay High crude oil. None of these isolates degraded the aromatic or ashphaltene fractions. All the isolates required aeration, nitrogen and phosphate supplementation for optimal degradation. Four out of the six yeasts are human pathogens.

Emulsifier from a tropical marine yeast, Yarrowia lipolytica NCIM 3589

A tropical marine strain of Yarrowia lipolytica, NCIM 3589 produced emulsifier in the presence of alkanes or crude oil. The mode of alkane uptake in this organism was by attachment to large droplets. An emulsifier (lipid‐carbohydrate‐protein) complex was associated with the cell wall. This emulsifier increased the hydrophobicity of the cells during the growth phase. In the stationary phase, the organism produced the emulsifier extracellularly under conditions of carbon excess and nitrogen limitation. Other requirements for extracellular emulsifier production included an initial pH of 8.0 and the presence of sodium chloride at a concentration of 2 to 3% (342 to 513 mM). The cell‐associated and extracellular emulsifier was shown to have similar properties.

Single cell oil of oleaginous fungi from the tropical mangrove wetlands as a potential feedstock for biodiesel

BackgroundSingle cell oils (SCOs) accumulated by oleaginous fungi have emerged as a potential alternative feedstock for biodiesel production. Though fungi from mangrove ecosystem have been reported for production of several lignocellulolytic enzymes, they remain unexplored for their SCO producing ability. Thus, these oleaginous fungi from the mangrove ecosystem could be suitable candidates for production of SCOs from lignocellulosic biomass. The accumulation of lipids being species specific, strain selection is critical and therefore, it is of importance to evaluate the fungal diversity of mangrove wetlands. The whole cells of these fungi were investigated with respect to oleaginicity, cell mass, lipid content, fatty acid methyl ester profiles and physicochemical properties of transesterified SCOs in order to explore their potential for biodiesel production.ResultsIn the present study, 14 yeasts and filamentous fungi were isolated from the detritus based mangrove wetlands along the Indian west coast. Nile red staining revealed that lipid bodies were present in 5 of the 14 fungal isolates. Lipid extraction showed that these fungi were able to accumulate > 20% (w/w) of their dry cell mass (4.14 - 6.44 g L-1) as lipids with neutral lipid as the major fraction. The profile of transesterified SCOs revealed a high content of saturated and monounsaturated fatty acids i.e., palmitic (C16:0), stearic (C18:0) and oleic (C18:1) acids similar to conventional vegetable oils used for biodiesel production. The experimentally determined and predicted biodiesel properties for 3 fungal isolates correlated well with the specified standards. Isolate IBB M1, with the highest SCO yield and containing high amounts of saturated and monounsaturated fatty acid was identified as Aspergillus terreus using morphotaxonomic study and 18 S rRNA gene sequencing. Batch flask cultures with varying initial glucose concentration revealed that maximal cell biomass and lipid content were obtained at 30gL-1. The strain was able to utilize cheap renewable substrates viz., sugarcane bagasse, grape stalk, groundnut shells and cheese whey for SCO production.ConclusionOur study suggests that SCOs of oleaginous fungi from the mangrove wetlands of the Indian west coast could be used as a potential feedstock for biodiesel production with Aspergillus terreus IBB M1 as a promising candidate.

Dimorphic transition in Yarrowia lipolytica isolated from oil-polluted sea water

Fungal cultures isolated from oil-polluted sea water near Mumbai, India have been studied for their capability to degrade crude oil. A yeast isolate identified as Yarrowia lipolytica was further investigated with respect to its dimorphic behaviour and alkane degradation. Y. lipolytica NCIM 3589 in the yeast form degraded the aliphatic fraction of crude oil and also pure alkanes (20-60% within 48 h) under aerobic conditions. Unlike most Y. lipolytica strains, our isolate required partial anaerobiosis for mycelium formation. Studies with two isolates suggested that mycelium to yeast transition may be the prerequisite for effective alkane degradation.

Isolation of an emulsifier from Yarrowia lipolytica NCIM 3589 using a modified mini isoelectric focusing unit

A Yarrowia lipolytica strain (NCIM 3589) isolated in our laboratory produced an emulsifier during the stationary phase when grown in a defined artificial sea water medium containing 1% (v/v) n‐hexadecane, as the sole carbon source. The emulsifier was isolated by ultrafiltration, Sepharose 4B followed by isoelectric focusing (IEF) in a miniscale unit in the pH range of 3·0–10 and 3·5–5·0. The pI of the emulsifier was 4·0. The emulsifier is a glycolipid consisting of 5% protein, 20% carbohydrate and 75% lipid. The fatty acid, sugar and amino acid composition of the isolated emulsifier are described along with temperature stability, pH stability and stability in sodium chloride. This paper is a first report on rapid and simple isolation by IEF of a microbial emulsifier.

Crude oil degradation by free and immobilized cells of Yarrowia lipolytica NCIM 3589

Abstract Crude oil degradation by a strain of Yarrowia lipolytica isolated from a chronically oil‐contaminated tropical marine estuary was studied in free and immobilized form. The strain degraded 78 % of the aliphatic fraction of Bombay High crude oil in the free form under optimal conditions. Immobilized in porous agar beads, the cells degraded upto 92% of the aliphatic fraction of supplied oil at 30°C, 200 rpm and crude oil concentrations of 1 % w/v. The immobilized cells were effective upto five cycles each of five days with 28% loss of activity in batch culture. In a continuous flow reactor, immobilized cells were active for 30 days, the duration of the experiment, with no loss of activity.

Double-stranded RNA from a marine alkane-degrading yeast Yarrowia lipolytica

A strain of Yarrowia lipolytica isolated from a tropical estuarine environment showed the presence of a double-stranded RNA. The double-stranded RNA had a molecular size of 5kb and a G+C content of 61 mole%. The strain was not a killer. No specific physiological function could be assigned to this plasmid.