Unravelling Metagenomics Approach for Microbial Biofuel Production.

Renewable biofuels, such as biodiesel, bioethanol, and biobutanol, serve as long-term solutions to fossil fuel depletion. A sustainable approach feedstock for their production is plant biomass, which is degraded to sugars with the aid of microbes-derived enzymes, followed by microbial conversion of those sugars to biofuels. Considering their global demand, additional efforts have been made for their large-scale production, which is ultimately leading breakthrough research in biomass energy. Metagenomics is a powerful tool allowing for functional gene analysis and new enzyme discovery. Thus, the present article summarizes the revolutionary advances of metagenomics in the biofuel industry and enlightens the importance of unexplored habitats for novel gene or enzyme mining. Moreover, it also accentuates metagenomics potentials to explore uncultivable microbiomes as well as enzymes associated with them.

Utilization of Clarified Butter Sediment Waste as a Feedstock for Cost-Effective Production of Biodiesel.

The rising demand and cost of fossil fuels (diesel and gasoline), together with the need for sustainable, alternative, and renewable energy sources have increased the interest for biomass-based fuels such as biodiesel. Among renewable sources of biofuels, biodiesel is particularly attractive as it can be used in conventional diesel engines without any modification. Oleaginous yeasts are excellent oil producers that can grow easily on various types of hydrophilic and hydrophobic waste streams that are used as feedstock for single cell oils and subsequently biodiesel production. In this study, cultivation of Rhodosporidium kratochvilovae on a hydrophobic waste (clarified butter sediment waste medium (CBM)) resulted in considerably high lipid accumulation (70.74% w/w). Maximum cell dry weight and total lipid production were 15.52 g/L and 10.98 g/L, respectively, following cultivation in CBM for 144 h. Neutral lipids were found to accumulate in the lipid bodies of cells, as visualized by BODIPY staining and fluorescence microscopy. Cells grown in CBM showed large and dispersed lipid droplets in the intracellular compartment. The fatty acid profile of biodiesel obtained after transesterification was analyzed by gas chromatography-mass spectrometry (GC-MS), while its quality was determined to comply with ASTM 6751 and EN 14214 international standards. Hence, clarified sediment waste can be exploited as a cost-effective renewable feedstock for biodiesel production.

Biodegradation of phenol via meta cleavage pathway triggers de novo TAG biosynthesis pathway in oleaginous yeast.

Phenol is reported to be one of the most toxic environmental pollutants present in the discharge of various industrial effluents causing a serious threat to the existing biome. Biodegradation of phenol by oleaginous yeast Rhodosporidium kratochvilovae HIMPA1 was found to degrade 1000mg/l phenol. The pathways for phenol degradation by both ortho and meta-cleavage were proposed by the identification of metabolites and enzymatic assays of ring cleavage enzymes in the cell extracts. Results suggest that this oleaginous yeast degrade phenol via meta-cleavage pathway and accumulates a high quantity of lipid content (64.92%; wt/wt) as compared to control glucose synthetic medium (GSM). Meta-cleavage pathway of phenol degradation leads to formation of pyruvate and acetaldehyde. Both these end products feed as precursors for de novo triacylglycerols (TAG) biosynthesis pathway which causes accumulation of TAG in the lipid droplets (LD) of 6.12±0.78µm grown on phenol while 2.38±0.52µm observed on GSM. This was confirmed by fluorescence microscopic images of BODIPY505-515nm stained live yeast cells. GC-MS analysis of extracted total lipid showed enhanced amount of monounsaturated fatty acid (MUFA) which was as 51.87%, 58.33% and 62.98% in presence of 0.5, 0.75 and 1g/l of phenol.

Bioremediation of domestic and industrial wastewaters integrated with enhanced biodiesel production using novel oleaginous microalgae.

The study illustrates the synergistic potential of novel microalgal, Chlamydomonas debaryana IITRIND3, for phycoremediation of domestic, sewage, paper mill and dairy wastewaters and then subsequent utilisation of its biomass for biodiesel production. Among these wastewaters, maximum lipid productivity (87.5 ± 2.3 mg L-1 day-1) was obtained in dairy wastewater with removal efficiency of total nitrogen, total phosphorous, chemical oxygen demand and total organic carbon to be 87.56, 82.17, 78.57 and 85.97 %, respectively. Metal ions such as sodium, calcium, potassium and magnesium were also removed efficiently from the wastewaters tested. Pigment analysis revealed loss of chlorophyll a while increase in carotenoid content in algal cells cultivated in different wastewaters. Biochemical data of microalgae grown in different wastewaters showed reduction in protein content with an increase in carbohydrate and lipid contents. The major fatty acids in algal cells grown in dairy wastewater were C14:0, C16:0, C16:1, C18:0, C18:2 and C18:3. The physical properties of biodiesel derived from microalgae grown in dairy wastewater were in compliance with the ASTM D6751 and EN 14214 fuel standards and were comparable to plant oil methyl esters.