Showing papers by "Rajeev K. Sukumaran published in 2020"

Mild alkaline pretreatment can achieve high hydrolytic and fermentation efficiencies for rice straw conversion to bioethanol.

Abstract: Mild alkaline pretreatment was evaluated as a strategy for effective lignin removal and hydrolysis of rice straw. The pretreatment efficiency of different NaOH concentrations (0.5, 1.0, 1.5 or 2.0%...

Evaluation of Freshwater Microalgal Isolates for Growth and Oil Production in Seawater Medium

Abstract: Microalgal cells have the potential to rapidly accumulate lipids which find applications as biodiesel production and nutraceuticals (e.g., EPA and DHA). Seawater is considered as an attractive medium for cultivation of microalgae since it contains most of the mineral nutrients. Besides, it offers the advantage of lesser bacterial and fungal contamination which is the main cause of decreased biomass productivity in open pond cultivation of freshwater microalgae. The present work describes the screening of freshwater microalgal isolates for production of biomass and lipids in a seawater based medium against freshwater medium under phototrophic cultivation. Isolate RAP-13, RI67-1 and R167-3 had maximum biomass production, whereas lipid yield was highest in the isolate RAP-13(67 mg/l). The potent isolate RAP-13 identified as Chlorococcum sp., was able to grow under a wide range of pH (4–10) in the seawater medium. Freshwater microalgae adapted well and yielded more lipids in seawater medium indicating the potential to cultivate them in marine water reducing the freshwater footprint.

Penicillium janthinellum NCIM1366 shows improved biomass hydrolysis and a larger number of CAZymes with higher induction levels over Trichoderma reesei RUT-C30.

Abstract: Major cost of bioethanol is attributed to enzymes employed in biomass hydrolysis. Biomass hydrolyzing enzymes are predominantly produced from the hyper-cellulolytic mutant filamentous fungus Trichoderma reesei RUT-C30. Several decades of research have failed to provide an industrial grade organism other than T. reesei, capable of producing higher titers of an effective synergistic biomass hydrolyzing enzyme cocktail. Penicillium janthinellum NCIM1366 was reported as a cellulase hyper producer and a potential alternative to T. reesei, but a comparison of their hydrolytic performance was seldom attempted. Hydrolysis of acid or alkali-pretreated rice straw using cellulase enzyme preparations from P. janthinellum and T. reesei indicated 37 and 43% higher glucose release, respectively, with P. janthinellum enzymes. A comparison of these fungi with respect to their secreted enzymes indicated that the crude enzyme preparation from P. janthinellum showed 28% higher overall cellulase activity. It also had an exceptional tenfold higher beta-glucosidase activity compared to that of T. reesei, leading to a lower cellobiose accumulation and thus alleviating the feedback inhibition. P. janthinellum secreted more number of proteins to the extracellular medium whose total concentration was 1.8-fold higher than T. reesei. Secretome analyses of the two fungi revealed higher number of CAZymes and a higher relative abundance of cellulases upon cellulose induction in the fungus. The results revealed the ability of P. janthinellum for efficient biomass degradation through hyper cellulase production, and it outperformed the established industrial cellulase producer T. reesei in the hydrolysis experiments. A higher level of induction, larger number of secreted CAZymes and a high relative proportion of BGL to cellulases indicate the possible reasons for its performance advantage in biomass hydrolysis.

Lipase of Pseudomonas guariconesis as an additive in laundry detergents and transesterification biocatalysts.

Abstract: A newly isolated culture, Pseudomonas guariconesis, is reported for the first time for lipase production. Various process parameters affecting enzyme production were optimized through statistical design experiments. The Plackett-Burman experimental design was used for screening 10 parameters for lipase production, which was further optimized using the central composite design of response surface methodology. Maximum lipase activity of 220 U/ml was obtained after 24 h of incubation in shake-flask cultures with an inoculum concentration of 0.6% v/v, incubation temperature of 30°C, and medium pH 9.0. Castor oil (0.5% v/v) was used as the inducer for lipase production. The enzyme was found to be compatible with five different commercial detergents, indicating its potential to be used in detergent formulations. It also acted as a biocatalyst in a transesterification process. The alkaline enzyme was found to be stable in the presence of bleaching agents, metal ions, and organic solvents as well.

Fumaric acid production from sugarcane trash hydrolysate using Rhizopus oryzae NIIST 1

Abstract: Production of organic acids through fermentation of biomass feedstock is a potent strategy for co-product generation and improving economics in lignocellulose biorefinery. Sugar cane trash (SCT), a surplus available agro-residue, was exploited for the production of fumaric acid - a dicarboxylic acid with applications in the synthesis of polyester resins, as mordant and as a food additive. The isolate NIIST 1 which showed the production of fumaric acid was identified as Rhizopus oryzae . Media engineering was carried out and a maximum production of fumaric acid in SCT hydrolysate incorporated media was 5.2 g/L. Response surface analyses of the interaction of parameters indicated the importance of maintaining a high C/N ratio. Results indicate the scope for developing the Rhizopus oryzae strain NIIST 1 as a potent organism for fumaric acid production, since only a few microorganisms have the ability to produce industrially relevant compounds using lignocellulose biomass hydrolysates.

Efflux mediated chlorpyrifos tolerance in Escherichia coli BL21(DE3)

Abstract: Bacteria are continually challenged with variety of synthetic chemicals/xenobiotics in their immediate surroundings, including pesticides. Chlorpyrifos is one of the most commonly used organophosphate pesticides in the world. The non-environmental strain of Escherichia coli, BL21 (DE3) displayed high tolerance to chlorpyrifos but with no/negligible degradation. The intrinsic resistance mechanisms that aid the organism in its high tolerance are probed. Efflux pumps being ubiquitous in nature and capable of conferring resistance against wide variety of xenobiotics were found to be over-expressed in the presence of CP. Also, an efflux pump inhibitor PAβN increased the susceptibility of E. coli to chlorpyrifos due to the intracellular accumulation of CP. The tripartite efflux pump EmrAB-TolC with increased expression in both transcript and protein on CP exposure, might play a major role in CP tolerance. The transcriptional regulators involved in multidrug resistance along with transporters belonging to all the major families conferring antimicrobial resistance were up-regulated. Also up-regulated were the genes involved in phopshonate metabolism and all the genes in the copper or silver export system. The common resistance mechanisms i.e, activation of efflux pumps between CP, antibacterial metals and antibiotics resistance might result in cross-resistance, ultimately increasing the prevalence of multidrug resistant strains, making infections hard to treat.