Biochemical study on marine diatoms for biodiesel production
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Date
2019
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DEPARTMENT OF BIOCHEMISTRY AND BIOCHEMICAL ENGINEERING, JACOB INSTITUTE OF BIOTECHNOLOGY AND BIOENGINEERING, SAM HIGGINBOTTOM UNIVERSITY OF AGRICULTURE, TECHNOLOGY AND SCIENCES, ALLAHABAD- 211007
Abstract
Sample (marine diatoms) were collected and isolated from Vellar estuary, Southeast coast of India (Bay of Bengal) in July-2014. Pure cultures of two species were subjected to morphological identification and DNA barcoding (rbcL gene sequencing). From the data two new strains of Odontella aurita (Accession number KR733098) and Chaetoceros muelleri (Accession number KR733100) were identified. Highest cell density for both the diatoms cultured in Guilard‟s f/2 nutrient medium under Si stress (53, 106 and 159μM Si) was observed on day 11. The highest increase the total lipid content in O. aurita and C. muelleri was 23.7±0.79 % and 25.6 ±0.48 % of dry biomass respectively under 53 μM Si stress. However, highest increase in cell density of 85.63 % and 45.93% as compared to the control was reported under 159 μM Si stress in O. aurita and C. muelleri respectively. Lipids extracted from both diatoms under 53 μM Si stress were transesterified (FAME) and analysed via GC-MS. In O. aurita FAME constituted: 43.61% SFA methyl esters, 33.22% MUFA methyl esters and 23.17% PUFA methyl esters whilst C. muelleri lipids contained was 69.62% SFA methyl esters, 16.53% MUFA methyl esters and 13.85% PUFA methyl esters. Three key enzymes involved lipid biosynthesis (acetyl Co-A carboxylase-EC 6.4.1.2, pyruvate dehydrogenase complex-EC 1.2.4.1 and malate dehydrogenase-EC 1.1.1.37) were also assayed in the crude extracts of the two species. As compared to control, activities of all three enzymes increased under 53μM Si stress. A similar trend was observed in the specific activities as well. The highest activity amongst the three enzymes assayed was reported for malate dehydrogenase at 53 μM Si stress in both species (737.46±14.5 for O. aurita and 777.46±22.1 for C. muelleri). This could be interpreted as a response to cope with onset of Si stress. The order of enzyme activity across treatments was: malate dehydrogenase > pyruvate dehydrogenase complex > acetyl Co-A carboxylase. A pH and temperature dependence was also observed. The results suggest that regulation of lipid biosynthesis under Si stress in O. aurita and C. muelleri is effected by the activity of these enzymes. However, a more detailed study is required to understand the underlying complex mechanisms. As compared to Odontella aurita (KR733098), Chaetoceros muelleri (KR733100) under 53μM Si stress is a probable indigenous species for biodiesel production.
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Ph. D. Thesis
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