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Improvement of agitation is a commonly used approach for the optimization of fermentation processes. In this report, the response to improving agitation rate from 150 to 250 rpm on cellulase production from Penicillium decumbens JUA10-1 was investigated. It was shown that the production of all the major components of the cellulase mixture increased following improved agitation. Further investigations showed that at least three factors are involved in this improvement: the improved biomass accumulation, proportion of active/mature cellulases, and cellulase transcription level. The transcription levels of the cellulase repressing transcription factor ace1 and the cellulase activating transcription factor xlnR, however, both declined when a higher agitation was applied. These observations, along with our analysis of the carbon catabolite repressor CreA, lead to the suggestion that the molecular mechanism underlying improved cellulase transcription is the competition of two concurrent effects following improved agitation: CreA-mediated derepression induced by the downregulation of ace1, and CreA-mediated deactivation induced by the downregulation of xlnR. [ABSTRACT FROM AUTHOR]

The increasing petroleum price and the foreseeable depletion of fossil fuels has prompted research on bioenergy, particularly bioethanol and biobutanol from renewable lignocellulosic biomass, the primary component of which is cellulose. One key requirement of lignocellulose degradation is to improve the efficiency of a group of enzymes with general name cellulase, the collaboration of which degrades cellulose to glucose. Significant progress has been made in the last decade on understanding the structural and chemical properties of the substrate cellulose, the structural and biochemical properties of cellulases, their enzymatic mechanisms and the mechanism of synergistic catalysis by cellulases. This manuscript reviews the progress in the aforementioned fields, particularly the structural basis and enzymatic mechanisms of reactions leading to the degradation of cellulose. Based on these discoveries, popular models of enzymatic cellulose degradation are discussed, in the hope of benefiting further in-depth investigations of this complex, multi-component enzymatic reaction.© 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The potential of cellulase enzymes in the developing and ongoing “biorefinery” industry has provided a great motivation to develop an efficient cellulase mixture. Recent work has shown how important the role that the so-called accessory enzymes can play in an effective enzymatic hydrolysis. In this study, three newest Novozymes Cellic CTec cellulase preparations (CTec 1/2/3) were compared to hydrolyze steam pretreated lignocellulosic substrates and model substances at an identical FPA loading. These cellulase preparations were found to display significantly different hydrolytic performances irrelevant with the FPA. And this difference was even observed on the filter paper itself when the FPA based assay was revisited. The analysis of specific enzyme activity in cellulase preparations demonstrated that different accessory enzymes were mainly responsible for the discrepancy of enzymatic hydrolysis between diversified substrates and various cellulases. Such the active role of accessory enzymes present in cellulase preparations was finally verified by supplementation with β-glucosidase, xylanase and lytic polysaccharide monooxygenases AA9. This paper provides new insights into the role of accessory enzymes, which can further provide a useful reference for the rational customization of cellulase cocktails in order to realize an efficient conversion of natural lignocellulosic substrates. [ABSTRACT FROM AUTHOR]