Combinatorial Engineering of Transcriptional Activators in Penicillium oxalicum for Improved Production of Corn-Fiber-Degrading Enzymes

Enzymatic conversion of corn fiber to fermentable sugars is beneficial to improving the economic efficiency of corn processing. In this work, the filamentous fungus Penicillium oxalicum was found to secrete enzymes for efficient saccharification of un-pretreated corn fiber. Separate engineering of transcriptional activators CIrB, XInR, and AraR led to enhanced production of different sets of lignocellulolytic enzymes. Particularly, the enzymes produced by XInR- and AraR-engineered strains showed a synergistic effect in corn fiber saccharification. Combinatorial engineering of all three activators generated a strain MCAX with 3.1-to 51.0-fold increases in lignocellulolytic enzyme production compared with the parent strain. In addition, the enzymes of strain MCAX released significantly more fermentable sugars from corn fiber than those of the parent strain at the same protein dosage. The results suggest that this strain has potential for on-site production of enzymes for corn fiber saccharification.

Automated summary

Enzymatic conversion of corn fiber to fermentable sugars by Penicillium oxalicum is efficient. Engineering of transcriptional activators CIrB, XInR, and AraR leads to increased production of lignocellulolytic enzymes, with synergistic effects observed in un-pretreated corn fiber saccharification. Combinatorial engineering of all three activators generated a strain MCAX with significantly higher lignocellulolytic enzyme production and higher sugar release efficiency from corn fiber.