No abstract

Application of multiple response optimizations using desirability function in the production of microbial metabolites improves economy and efficiency. Concurrent production of cellulase and xylanase in Trichoderma reesei NCIM 1186 using an agricultural weed, Prosopis juliflora pods, was studied. The main aim of the study was to optimize significant medium nutrient parameters for maximization of cellulase and xylanase by multi-objective optimization strategy using biomass. Process parameters such as the nutrient concentrations (pods, sucrose, and yeast extract) and pH were investigated to improve cellulase and xylanase activities by one factor at a time approach, single response optimization and multi-objective optimization. At the corresponding optimized process parameters in single response optimization, the maximum cellulase activity observed was 3055.65 U/L where xylanase highest activity was 422.16 U/L. Similarly, the maximum xylanase activity, 444.94 U/L, was observed with the highest cellulase activity of 2804.40 U/L. The multi-objective optimization finds a tradeoff between the two objectives and optimal activity values in between the single-objective optima were achieved, 3033.74 and 439.13 U/L for cellulase and xylanase, respectively.

No abstract

Lignocellulosic materials are abundant in nature but cannot be readily utilised as substrates for the fermentation due to their complexity. Breakdown of plant cell wall into easily utilisable substrates can be done by usage of enzymes like cellulases, xylanases and related enzymes. Cellulosome is a macromolecule which is a complex of such enzymes that act synergistically on lignocellulosic materials for complete degradation. Cellulosome have impressive applications in biotechnology as conversion of cellulosic biomass into simple sugars can be useful in the production of high-value products like organic acids and ethanol from inexpensive and renewable sources. Till date only some bacteria have shown the ability to produce cellulosomes. In present study, Trichoderma reesei NCIM 1186, cellulolytic fungi has been studied for its ability to produce cellulosome in Prosopis juliflora pods containing medium. In view of enhancing the cellulosome production, the effect of various carbon and nitrogen sources supplementation was studied using a statistical method, saturated Plackett-Burman (PB) design which is a modified version of PB. Seven carbon sources and eleven nitrogen sources were screened for their significant effect on the production of cellulosome. Out of tested carbon and nitrogen sources, maltose and ammonium hydrogen carbonate shown a significant effect on cellulase activity and maltose and ammonium sulphate shown a significant activity on xylanase activity of cellulosome.

The FACT (FAcilitates Chromatin Transactions) complex influences transcription initiation and enables passage of RNA polymerase (Pol) II through gene body nucleosomes during elongation. In the budding yeast, ∼280 noncoding RNA genes highly transcribed in vivo by Pol III are found in the nucleosome-free regions bordered by positioned nucleosomes. The downstream nucleosome dynamics was found to regulate transcription via controlling the gene terminator accessibility and hence, terminator-dependent Pol III recycling. As opposed to the enrichment at the 5′-ends of Pol II-transcribed genes, our genome-wide mapping found transcription-dependent enrichment of the FACT subunit Spt16 near the 3′-end of all Pol III-transcribed genes. Spt16 physically associates with the Pol III transcription complex and shows gene-specific occupancy levels on the individual genes. On the non-tRNA Pol III-transcribed genes, Spt16 facilitates transcription by reducing the nucleosome occupany on the gene body. On the tRNA genes, it maintains the position of the nucleosome at the 3′ gene end and affects transcription in a gene-specific manner. Under nutritional stress, Spt16 enrichment is abolished in the gene downstream region of all Pol III-transcribed genes and reciprocally changed on the induced or repressed Pol II-transcribed ESR genes. Under the heat and replicative stress, its occupancy on the Pol III-transcribed genes increases significantly. Our results show that Spt16 elicits a differential, gene-specific and stress-responsive dynamics, which provides a novel stress-sensor mechanism of regulating transcription against external stress. By primarily influencing the nucleosomal organization, FACT links the downstream nucleosome dynamics to transcription and environmental stress on the Pol III-transcribed genes.