The <i>TgRas1</i> Gene Affects the Lactose Metabolism of <i>Trichoderma guizhouense</i> NJAU4742

Abstract

Trichoderma is one of the fungi commonly used in fermentation engineering. The hydrolytic enzymes secreted by Trichoderma have great economic value. Trichoderma guizhouense NJAU4742 is a branch of Trichoderma harzianum, which also has application potential. Lactose can induce fungi to secrete cellulase. Unfortunately, neither the lactose-inducing effect nor the mechanism of lactose metabolism in the study of Trichoderma guizhouense NJAU4742 is clear. Our study showed that carbon sources such as glucose, galactose, and sucrose could not induce cellulase secretion from Trichoderma guizhouense NJAU4742. Lactose induced the filter paper activity of the cellulase secreted by Trichoderma to reach 4.13 ± 0.11 U·mL−1. The ratio of 0.4% lactose–0.6% straw is the best way to induce cellulase and is better than adding only straw or lactose. TgRas family genes respond differently to different carbon sources at the gene level, and these proteins may be involved in different carbon source metabolisms. The results of transcriptional responses under different growth conditions showed that TgRas1 occupies a dominant position among TgRas family genes. The growth of the ΔTgRas1 mutant on the plate was inhibited, and the hyphae were dense, thick, and swollen. Under the condition of lactose, the biomass of ΔTgRas1 was severely inhibited in liquid fermentation, and its biomass decreased by 91.43% compared with WT. The liquid fermentation of ΔTgRas1 under other carbon source conditions was not affected.

Keywords

• <i>Trichoderma guizhouense</i> NJAU4742
• <i>TgRas1</i>
• cellulase
• fermentation
• lactose metabolism