Search

Kresoxim-methyl residue in green chilli and soil was estimated using gas chromatography equipped with microelectron capture detector (µECD, 63Ni) and analytical method was validated. The method sho...

The atmospheric methane concentration is increasing rapidly at the rate of around 10 ppb/year. A concerted effort is required to reduce methane emission. Methanotrophs possess methane monooxygenase enzyme system and can consume a major portion of the methane produced in the environment. These microbes play a major role in the single-carbon-driven microbial food web. Microbial interaction is an important component of microbial ecology studies, and its role in community functioning and various biogeochemical cycles still remains unclear. A synergistic interaction occurs between the methanotrophs and non-methane-utilizing methylotrophs (NUM) in the natural ecosystem. The intermediates produced by the methanotrophs can be used as a carbon source by the NUM and support its existence. On the other hand, NUM consumes toxic intermediates like methanol and formaldehyde of the methanotrophs and prolongs their growth. The consumption of the intermediates (methanol, formaldehyde and formate) of the methane utilization pathway by methylotrophs as a result of cross-feeding enhances the methane utilization rate of that ecosystem. Co-inoculation of methanotrophs and NUM in the natural habitat particularly paddy ecosystem can aid in the reduction of net methane emission. This chapter highlights the role of microbial interactions, particularly between methanotrophs and methylotrophs, that can be harnessed to mitigate methane emission from the methane-rich environment.

Methane (CH4) emission in rice fields is greatly influenced by the type and quantity of nitrogenous fertilizer used. The net methane emission from paddy fields is also influenced by the activity of methane utilizing bacteria, which inhabit the flooded paddy ecosystem. Efficient methane utilizing and plant growth promoting bacteria Methylobacterium oryzae MNL7 and Paenibacillus polymyxa MaAL70, respectively were co-inoculated along with different nitrogenous fertilizer combinations in flooded paddy to assess their impact on cumulative methane emission and crop growth promotion. Co-inoculation significantly influenced the plant growth parameters of paddy, resulting in an increase in grain yield by 14.04, 11.08, and 12.38% in treatments receiving Urea, Di-ammonium Phosphate (DAP) + Urea, or farm yard manure (FYM), over their respective un-inoculated plots. Significant improvement in the rice grain nutrient quality in term of crude protein, Fe and Zn content was observed as a result of bacterial co-inoculation in FYM fertilized plots as compared to Urea and DAP+ Urea fertilized plots. Significantly higher cumulative methane emission of 63.39 kg ha−1 was observed in uninoculated plots fertilized with FYM treatment as compared to Urea (33.83 kg ha−1) and DAP+Urea (31.66 kg ha−1) treatments. Bacterial co-inoculation significantly reduced the cumulative methane emission by 12.03, 11.47 and 6.92% in Urea, DAP+Urea, and FYM fertilized plots over their respective uninoculated treatments. Among the different fertilizer treatments, bacterial co-inoculation with urea application performed significantly better in reducing cumulative methane emission. These findings suggest that methane utilizing bacteria which also possess plant growth promoting trait can be explored for developing a novel biofertilizer for flooded paddies, as they can aid in managing both the overall methane emission and enhancing crop yield.

Enzymatic hydrolysis is the most crucial step in bioconversion of lignocellulosic biomass to ethanol as efficient conversion of polymers to fermentable sugars determines final ethanol concentration. Cellulase complex used for commercial biomass hydrolysis is mostly derived from Trichoderma sp. and contains β-glucosidase

Lignocellulosic biomass is currently the most promising alternative energy source for realizing sustainable demands of agrarian economies. Its natural recalcitrance to degradation necessitates a detailed study on the complex biochemistry involved in bioconversion of this lignin–carbohydrate complex. A comprehension of the enzymology and role of principal and accessory glycosyl hydrolases involved in biomass degradation are, hence, noteworthy in this context and the xyloglucan-active hydrolases warrant special mention. These are enzymes which carry out hydrolysis and transglucosylation of xyloglucan, the major hemicellulosic polysaccharide in plant biomass. The structurally complex xyloglucans cover and cross-link the cellulosic microfibrils in plant cell walls and make cellulose inaccessible to saccharification by cellulases. Solubilisation of biomass polysaccharides and release of sugars are central to the biomass-to-bioethanol process. Complete conversion of biomass carbohydrates requires a suite of hydrolytic enzymes, which may be designed specifically to accommodate the predominant and subsidiary biomass-cleaving enzymes. Xyloglucan hydrolases which are known to act synergistically with cellulases and xylanases in loosening the plant cell wall are vital enzymes to be deployed for successful bioconversion processes. This chapter is an insight into the capacity of these accessory, but indispensable, hydrolytic enzymes in unlocking the inaccessible biomass polysaccharides for increased sugar recovery and thereby, in drafting the fuels of future.

Overall economics of the biomass to ethanol process is largely determined by the efficiency of biomass hydrolysis. Performance of cellulase cocktails used for saccharification of cellulose in biomass is often limited by lower amounts of β-glucosidases present, which catalyse hydrolysis of cellobiose, the product of endo and exocellulases to glucose. Inappropriate ratio of these enzymes in commercial cocktails leads to accumulation of cellobiose which inhibits the activity of cellulases. Thus, this rate limiting enzyme is of crucial importance in determining the efficiency of commercial cellulases. The saprophytic fungus Trichoderma sp., exploited for production of commercial cellulases, produces very minute quantities of β-glucosidases as compared to endo and exocellulases. However, several other organisms are known to produce β-glucosidases in higher quantities, over a broader substrate range. Strategies to get optimal ratio of exocellulases, endocellulases and β-glucosidases to enhance saccharification yields are, therefore, discussed. Appropriate levels of β-glucosidase activity in commercial cocktails have been obtained by supplementing with accessory β-glucosidases, transgenic approaches and by optimizing β-glucosidase production through manipulation of culture conditions. These approaches have resulted in achieving higher β-glucosidase activity in cellulase cocktails, facilitating higher sugar yields and thereby potentially improving enzymatic saccharification of biomass and eventually ethanol production.