Sukhendu Bikash Ghosh

Isolation and characterization of microalgae for biodiesel production from Nisargruna biogas plant effluent.

Increasing energy demand and depleting fossil fuel sources have intensified the focus on biofuel production. Microalgae have emerged as a desirable source for biofuel production because of high biomass and lipid production from waste water source. In this study, five microalgae were isolated from effluents of Nisargruna biogas plants. These isolates were identified based on morphology and partial 18S and 23S rRNA gene sequences. Growth and lipid accumulation potential of these microalgae were investigated. One isolate, Chlorella sp. KMN3, accumulated high biomass (1.59 ± 0.05 g L(-1)) with moderate lipid content (20%), while another isolate Monoraphidium sp. KMN5 showed moderate biomass accumulation of 0.65 ± 0.05 g L(-1) with a very high (35%) lipid content. The fatty acid methyl esters mainly composed of C-16:0, C-18:0, C-18:1 and C-18:2. This observation makes these microalgae immensely potential candidate for biodiesel production using the effluent of a biogas plant as feed stock.

Isolation and Identification of Arsenic Resistant Providencia rettgeri (KDM3) from Industrial Effluent Contaminated Soil and Studies on its Arsenic Resistance Mechanisma

A novel strain of Providencia rettgeri was isolated from metal contaminated industrial soil in Mumbai and was identified and characterized. This isolate could survive in a medium containing up to 10,000 μg mL-1 of arsenate (133.3 mM sodium arsenate). Growth parameter studies reveled that only at 5000 and 10000 μg mL-1 arsenic growth was retarded as compared to control cells. TEM studies indicated no major morphological changes or damages when cells were grown in presence of 10,000 μg mL-1 of arsenate. Arsenic treated cells as compared to untreated cells showed over expression of a protein, arsenical pump driving ATPase identified by MALDI TOF-Mass Spectrometry. Arsenate, once taken inside the cells, was presumably reduced to arsenite and further extruded out of the cells. The arsenic extrusion from the cells resulted in reduced accumulation of arsenic inside the cells as confirmed by TEMEDX and XPS analysis. The high resistance to arsenic by Providencia rettgeri was found to be plasmid mediated. Plasmid cured cells were sensitive to arsenic stress and could not grow in arsenic containing medium. Reduction of arsenate (V) to arsenite (III) by the present bacterial strain can contribute to mobility and bioavailability of arsenic in the soils. This is the first report of such high arsenic tolerance in Providencia sp. and it may have a very high potential for incorporating in an arsenic bioremediation strategy.