Medium Optimization and Transcriptomic Analysis of Tannase Production by Aspergillus niger NHF5
Aspergillus niger NHF5,which produced high tannase activity,was used as fermentation strain,response surface methodology was used to optimize its enzyme-producing medium.Finally,the optimal species and final concentrations of the three factors were determined as follow:glucose 1.5％,ammonium sulfate 1.25％,and tannic acid 2.5％.At this time,the enzyme activity of crude enzyme solution reached 192.85 U/mL,which was 4.4 times more active than the enzyme before optimization.In order to investigate the gene expression of Aspergillus niger NHF5 in fermentation medium,A total of 111 differentially expressed genes were identified by transcriptomic analysis,including 36 significantly up-regulated genes and 75 significantly down-regulated genes.GO enrichment analysis showed that the differentially expressed genes were mainly enriched in GO items such as molecular function,cell components,and biological processes.The enrichment of the KEGG pathway showed that only 7 of the 36 significantly up-regulated genes were involved in the metabolic pathway.Among these differentially expressed genes,16 carbohydrate-active enzymes were expressed,including ferulate esterase,glucose methanol choline oxidoreductase,tannase O-methyltransferase,and so on.The expression of carbohydrate esterase and glycoside hydrolase were the most abundant,accounting for 43.75％.The results not only provide technical guidance for the efficient production of tannase,but also provide theoretical exploration for the internal mechanism of tannase synthesis in strains.
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