Enhancement of Lignocellulolytic Enzyme Production in Penicillium oxalicum

The production of lignocellulolytic enzymes is transcriptionally regulated by multiple transcription factors. Liwei Gao, together with Shandong University researchers have previously engineered a Penicillium oxalicum for improved cellulase production via manipulation of three genes in the cellulase regulatory network. However, the potential of modifying multiple regulators while overexpressing their targets has not been fully explored.

The team recently verified that a point mutation XlnR^A871V in the transcription factor XlnR enhanced the expression of lignocellulolytic enzymes, particularly hemicellulases, in P. oxalicum. The overexpression of XlnR^A871V was then combined with the overexpression of the cellulase transcriptional activator ClrB and deletion of carbon catabolite repressor CreA.

The resulting strain RE-7 showed significant increases in cellulase and xylanase production compared to the starting strain. Further overexpression of two major cellulase genes cbh1-2 and eg1 enabled an additional 13% improvement in cellulase production. However, XlnR^A871V also led to decreased production of β-glucosidase and amylase due to reduced transcription of enzyme-encoding genes.

These results illustrate that combinational manipulation of transcription factors and their target genes can be a viable strategy for efficient production of lignocellulolytic enzymes in filamentous fungi.