High productivity of cellulase and xylanase enzymes in the mycelial-dispersed Pleurotus ostreatus Δpkac2 strain

Abstract

White-rot fungi secrete unique enzymes to degrade plant cell wall components. These enzymes have the potential to improve the effective utilization of lignocellulosic biomass in a bio-based society. In our previous study, pkac2-disrupted strains of Pleurotus ostreatus were applied for high-density liquid culture by improving mycelial dispersibility. In this study, we investigated the productivity and transcriptional profiles of wood-degrading enzymes of the Δpkac2 strain in the high-density liquid cultivation. Cellulase and xylanase activities in the culture filtrate of Δpkac2 strains in liquid shaking culture were 7.8- and 49-fold higher than those of the wild-type (WT) strain, respectively. In this condition, the mycelial dry weight of Δpkac2 strains was two-fold higher than that of the WT, showing their greater efficiencies for cellulase and xylanase production than the WT. RNA-Seq analysis indicated that 9 of 35 predicted cellulase genes and two of five predicted xylanase genes were significantly upregulated in the Δpkac2 strains. On the contrary, the transcript levels of laccase-encoding genes were significantly decreased, indicating that pkac2 is involved in their transcriptional regulation. These results indicate that the Δpkac2 strains have high potential to produce cellulase and xylanase in the high-density liquid cultivation by increasing mycelial growth as well as upregulating the expression of relevant genes.