Study Of The Mechanism On Cellulase Production From Filamentous Fungi

Lignocelluloseic biomass is the most abundant renewable materials on earth,which is degraded by cellulases.The most well-known lignocellulose-degraded filamentous fungi are Trichoderma reesei and Penicillium oxalicum,which are both industrial strains that produce cellulases.And cellulose was degraded into glucose.In this paper,the mechanism was studied on cellulase production from filamentous fungi.And this work consisted of two parts:1.T.reesei is a filamentous fungus naturally grown on solid lignocellulosic substrates,while most investigations on this key industrial microbe were performed in submerged cultures.The drastic difference between oxygen,water and substrate availability demands a clear understanding of the differences between T.reesei grown under the two conditions.In this work,by transcriptomic and physiological comparison between T.reesei wildtype QM6a strains grown under both solid-state and submerged conditions,fundamental physiological differences were found.The upregulation of sugar transport,glycolysis?metal ion uptake and oxidoreductases during submerged growth suggests a more robust energy metabolism,which is confirmed by a higher ATP content found in T.reesei grown on submerged conditions.On the other hand,during solid-state growth,both cellulose degradation and protein transport pathways are upregulated,suggesting improved utilization of lignocellulosic substrates.This finding also leads to the suggestion that the solid-state growth is a more 'natural' lifestyle.Indeed,T.reesei grown under submerged conditions suffers from environmental stress,as stress response and cellular membrane repair pathways are significantly upregulated.However,experimental evidence suggested that T.reesei in submerged media cannot cope with stress as well as solid-state-grown T.reesei.These discoveries give rise to the conclusion that the solid-state growth is a more 'natural' and resourceful growth condition,while the submerged growth is a more robust yet stressful growth condition.2.There is carbon catabolite repression(CCR)in Trichoderma reesei and Penicillium oxalicum.The research result proved that Crel/CreA is the major transcription factor on CCR.We speculated that the effect of Crel/CreA on CCR is related with its phosphorylation sites and three-dimentional structure.In this work,we constructed the mutants was obtained by mutagenesis of CreA.The results confirmed the T.reesei mutant has a great increase on the transcriptional level of the main cellulases gene.