Optimization Of Cellulose Production Conditions And Transcriptome Analysis Of Myceliophthora Thermophlia

Cellulose resources are important renewable resources in nature.Fungi can secrete cellulase to degrade cellulose.Currently,the most researched fungi for cellulose degradation at room temperature are Trichoderma and Aspergillus.However,their cellulase production systems are prone to contamination by other microorganisms and have low degradation efficiency.Therefore,it is necessary to discover and study new cellulose-degrading microorganisms and their cellulases.Thermophilic fungi can adapt to higher culture temperatures and have strong ability to produce cellulases to degrade cellulose.In this study,cellulose-degrading strains were obtained from the Lab.The effects of temperature,pH,carbon source,and nitrogen source on the growth of Myceliophthora thermophlia were investigated.Through orthogonal experimental design,the fermentation conditions for cellulase production by Myceliophthora thermophlia were optimized,including carbon source,nitrogen source,temperature,pH,and rotation speed,with carboxymethyl cellulase（CMCase）activity as the endpoint.The effects of temperature and pH on CMCase and the thermal and pH stability of CMCase were also studied.RNA-seq technology was used to perform transcriptome sequencing of Myceliophthora thermophlia,and the impact of using CMC-Na as the sole carbon source compared to glucose on gene expression was analyzed.Differential expression genes were compared with the database.The main conclusions are as follows:1.The effects of temperature,pH,carbon source,and nitrogen source on the growth of Myceliophthora thermophlia were investigated.The optimal growth temperature of Myceliophthora thermophlia on PDA medium was 40～45°C,and the optimal growth pH was 6～7.On seed culture medium,disaccharides such as sucrose as carbon sources,and organic nitrogen sources such as peptone and yeast extract were more conducive to the growth of Myceliophthora thermophlia.2.The optimized fermentation medium composition obtained through orthogonal experiment was as follows:glucose 2.0 g·L^-1,starch 3.0 g·L^-1,sucrose 15.0 g·L^-1,（NH₄）₂SO₄ 1.0 g·L^-1,yeast extract 3.0 g·L^-1,KH₂PO₄ 2.0 g·L^-1,Ca Cl₂·H₂O 0.3 g·L^-1,Mg SO₄·7H₂O 0.5 g·L^-1,Fe SO₄·7H₂O 0.005 g·L^-1.The optimized culture conditions were pH 5.5,culture temperature 50°C,and shaking speed 160 r·min^-1.3.The properties of crude enzyme solution from Myceliophthora thermophlia were studied.The optimal temperature for CMCase was 60～70°C,and the optimal pH was 5～6.CMCase showed thermal and acid resistance.4.RNA-seq technology was used to perform transcriptome sequencing analysis of Myceliophthora thermophlia cultured with carboxymethyl cellulose（CMC-Na）of glucose as the sole carbon sources.Compared to the glucose group,the CMC-Na group showed upregulation of 2443 genes and downregulation of 2151 genes.Differential gene analysis was performed by comparing these genes against the GO and KEGG databases.GO enrichment analysis revealed changes in genes related to the nucleus and ribosome synthesis and metabolism in the cellular component of Myceliophthora thermophlia.In the sucrose and starch metabolic pathways,there was significant upregulation of genes related to cellulose degradation,such as exoglucanase,endoglucanase,and β-glucosidase.