Enhancing the production of a heterologous Trametes laccase (LacA) by replacement of the major cellulase CBH1 in Trichoderma reesei

作者：Jiaxin Zhang, Yu Hong, Kehang Li, Yu Ting Sun, Yao Cheng, Jianya Ling, Yaohua Zhong · 发表于：Journal of Industrial Microbiology & Biotechnology · 年份：2023 · DOI：10.1093/jimb/kuad002 · 被引用次数：22 · 研究领域：Enzyme-mediated dye degradation、Fungal and yeast genetics research、Fermentation and Sensory Analysis

The laccases from white-rot fungi exhibit high redox potential in treating phenolic compounds. However, their application in commercial purposes has been limited because of the relatively low productivity of the native hosts. Here, the laccase A-encoding gene lacA of Trametes sp. AH28-2 was overexpressed under the control of the strong promoter of cbh1 (Pcbh1), the gene encoding the endogenous cellobiohydrolase 1 (CBH1), in the industrial workhorse fungus Trichoderma reesei. Firstly, the lacA expression cassette was randomly integrated into the T. reesei chromosome by genetic transformation. The lacA gene was successfully transcribed, but the laccase couldn't be detected in the liquid fermentation condition. Meanwhile, it was found that the endoplasmic reticulum-associated degradation (ERAD) was strongly activated, indicating that the expression of LacA probably triggered intense endoplasmic reticulum (ER) stress. Subsequently, the lacA expression cassette was added with the downstream region of cbh1 (Tcbh1) to construct the new expression cassette lacA::Δcbh1, which could replace the cbh1 locus in the genome via homologous recombination. After genetic transformation, the lacA gene was integrated into the cbh1 locus and transcribed. And the unfolded protein response (UPR) and ERAD were only slightly induced, for which the loss of endogenous cellulase CBH1 released the pressure of secretion. Finally, the maximum laccase activity of 168.3 U/l was obtained in the fermentation br...