Sourish Bhattacharya

Fatty acids as biomarkers of microalgae

Microalgae are primary producers of the food chain and hold prominence towards pharmaceutical and nutraceutical applications. Fatty acids (FAs) are one of the primary metabolites of microalgae, which enrich their utility both in the form of food and fuels. Additionally, the vast structural diversity coupled with taxonomic specificity makes these FAs as potential biomarkers. The determination of lipid and fatty acid profiling of 12 different strains of microalgae has been accomplished in this study and further discussed in respect to their chemotaxonomic perspective in microalgae. Palmitic acid (C16:0) and oleic acid (C18:1n9c) were found to be dominant among the members of Cyanophyceae whereas members of Chlorophyceae were rich in palmitic acid (C16:0), oleic acid (C18:1n9c) and linoleic acid (C18:2n6). The application of principal component analysis (PCA) and algorithmic hierarchical clustering (AHC) resulted in the segregation of the studied microalgal strains into 8 different orders belonging to 2 distinct phyla according to their phylogenetic classification. Nutritionally important FAs like eicosapentaenoic acid (EPA, C20:5n3) and docosahexaenoic acid (DHA, C22:6n3) were detected only in Chlorella sp. belonging to Chlorophyceaen family. Differential segregation of microalgae with respect to their fatty acid profile indicated the potential utility of FAs as biomarkers.

Comparative evaluation of chemical and enzymatic saccharification of mixotrophically grown de-oiled microalgal biomass for reducing sugar production

For the commercialization of microalgal based biofuels, utilization of de-oiled carbohydrate rich biomass is important. In the present study, chemo-enzymatic hydrolysis of mixotrophically grown Scenedesmus sp. CCNM 1077 de-oiled biomass is evaluated. Among the chemical hydrolysis, use of 0.5M HCl for 45 min at 121°C resulted in highest saccharification yield of 37.87% w/w of de-oiled biomass. However, enzymatic hydrolysis using Viscozyme L at loading rate of 20 FBGU/g of de-oiled biomass, pH 5.5 and temperature 45°C for 72 h resulted in saccharification yield of 43.44% w/w of de-oiled biomass. Further, 78% ethanol production efficiency was achieved with enzymatically hydrolyzed de-oiled biomass using yeast Saccharomyces cerevisiae ATCC 6793. These findings of the present study show application of mixotrophically grown de-oiled biomass of Scenedesmus sp. CCNM 1077 as promising feedstock for bioethanol production.

Biodegradable Polymeric Substances Produced by a Marine Bacterium from a Surplus Stream of the Biodiesel Industry

Crude glycerol is generated as a by-product during transesterification process and during hydrolysis of fat in the soap-manufacturing process, and poses a problem for waste management. In the present approach, an efficient process was designed for simultaneous production of 0.2 g/L extracellular ε-polylysine and 64.6% (w/w) intracellular polyhydroxyalkanoate (PHA) in the same fermentation broth (1 L shake flask) utilizing Jatropha biodiesel waste residues as carbon rich source by marine bacterial strain (Bacillus licheniformis PL26), isolated from west coast of India. The synthesized ε-polylysine and polyhydroxyalkanoate PHA by Bacillus licheniformis PL26 was characterized by thermogravimetric analysis (TGA), differential scanning colorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and 1H Nuclear magnetic resonance spectroscopy (NMR). The PHA produced by Bacillus licheniformis was found to be poly-3-hydroxybutyrate-co-3-hydroxyvalerate (P3HB-co-3HV). The developed process needs to be statistically optimized further for gaining still better yield of both the products in an efficient manner.

Challenges in the Design and Operation of an Efficient Photobioreactor for Microalgae Cultivation and Hydrogen Production

The major challenge in the production of biofuels from microalgae is the need to generate sufficient quantities of microalgal biomass and an environmentally friendly and cost-effective method for extraction of oil from the biomass. Biomass can be generated by cultivating microalgae in open ponds or closed photobioreactor systems. When using a photobioreactor system, it is possible to have better control over parameters such as temperature, pH, light intensity, dissolved oxygen and dissolved carbon dioxide. However, they consume more energy and are expensive to operate. Cultivation of microalgae in open ponds is cheaper, and it utilises less energy as compared to closed photobioreactors. But, it is not possible to control physical parameters like temperature and light intensity as they depend on the environmental conditions. Also, contamination from other predators, parasites and weeds needs to be addressed. Considering, the overall cost-effectiveness, it may be possible to cultivate microalgae in open ponds under semi-continuous systems. Direct production of hydrogen using photosynthetic microorganisms such as microalgae may also be considered since it can be energetically more favourable than cultivating, harvesting and processing the biomass for biofuel production. In such cases, degradation of the hydrogen produced by the hydrogenase enzyme present in the system needs to be managed. Considering future energy demands, the possibility of CO2 sequestration and bioenergy production from microalgae and the overall ease of cultivation, it may be possible to use semi-continuous cultivation in open ponds for generating microalgal biomass with better biomass yield.

High concentration solubility and stability of ɛ-poly-l-lysine in an ammonium-based ionic liquid: A suitable media for polypeptide packaging and biomaterial preparation

Packaging of structurally sensitive biomolecules such as proteins, peptides and DNA in non-aqueous media at ambient conditions with chemical and structural stability is important to explore the potential of such biomacromolecules as substrate for functional biomaterial design and for biotechnological applications. In this perspective, solubility, chemical and structural stability of ɛ-poly-l-lysine (ɛ-PL), a homopolypeptide produced by Streptomyces albulus in different ionic liquids (ILs) namely 2-hydroxyethyl ammonium formate (2-HEAF), 2-hydroxyethyl ammonium acetate (2-HEAA), choline formate (Ch-Formate) and choline acetate (Ch-Acetate) was studied. Maximum solubility (15% w/v) of the homopolypeptide was observed in 2-HEAF and lowest was found in Ch-Formate (2% w/v). After regeneration of the dissolved polypeptide in the IL, the IL could be recycled and reused in the dissolution process. Unlike in other ILs, 3-15% w/v of ɛ-PL in 2-HEAF gave formation of a thixotropic thermoreversible soft gel. Molecular docking studies established favourable interactions of [2-HEA]+ cation over [Ch]+ with ɛ-PL indicating [2-HEA]+ as the most promising cation for the dissolution process. However, the role of the anions was also found to be important, which could lead to improvement in polypeptide solubility when combined to the selected cation. The findings demonstrate suitability of the ionic liquids for functionalization of polypeptides for biomaterial preparation.

Stability of Phycobiliproteins Using Natural Preservative ε- Polylysine (ε-PL)

C-Phycocyanin (PC) and C-Phycoerythrin (PE) are important phycobiliproteins (PBs) with their possible application as colorants in food industries. In the present study, effect of natural preservative, e-polylysine and chemical preservative, citric acid on the stability of C-PC and C-PE at 4 ± 2°C was studied. Percentage loss of C-PE and C-PC content and effect of pH and fluorescence on C-PC and C-PE was studied. 0.02% e-polylysine (w/v) was found to be optimum for storage of C-PC and C-PE at 4 ± 2°C and lesser loss of C-PC and C-PE content as compared to citric acid for its storage up to 8 days without any change in colour and pH. The amount of C-PC and CPE left in the solution containing e-polylysine was 90.5 and 95.24% respectively. 0.02% e-polylysine (w/v) was found to be optimum for storage of C-PC and C-PE at 4 ± 2°C and lesser loss of CPC and C-PE content as compared to citric acid for its storage up to 8 days without any change in colour and pH. The amount of C-PC and C-PE left in the solution containing e-polylysine was 90.5 and 95.24% respectively. Further, there is a need to replace chemical or synthetic preservatives with natural preservative ɛ-polylysine as prolonged consumption of these chemical or synthetic preservatives possess health hazard. The present work provides an effective option for replacing these chemical or synthetic preservatives with e-polylysine as natural preservative.