Phanerochaete chrysosporium produces a diverse array of extracellular enzymes when grown on sorghum

Abstract

In an effort to understand how fungi degrade biomass, we grew Phanerochaete chrysosporium on sorghum stover and chronicled the growth of the fungus over the course of 14 days. The fungal mass grew steadily until the fifth day, reaching 0.06 mg of cells per milligram of dry mass, which fell by the seventh day and stayed at nearly the same level until day 14. After 1 day, hemicellulases, cellulases, and polygalacturonases were detected in the extracellular fluid at 1.06, 0.34, and 0.20 U/ml, respectively. Proteomic studies performed with the extracellular fluid using liquid chromatography–tandem mass spectrometry identified 57, 116, and 102 degradative enzymes targeting cellulose, hemicellulose, pectin, lignin, proteins, and lipids on days 1, 7, and 14, respectively. Significant concentrations of breakdown products of the sorghum polysaccharides were detected in the extracellular fluid indicating that the enzymes were breaking the polysaccharides, and after 14 days, almost 39% of the sorghum sugars had been used by the fungus. Our results suggest that P. chrysosporium produces a set of enzymes to degrade the components of lignocellulose from the beginning of its growth, but modifies the complement of enzymes it secretes over time to adapt to the particular substrate available.

Discovery of LPMO activity on hemicelluloses shows the importance of oxidative processes in plant cell wall degradation

“…hemicelluloses (20,36,37). Third, apart from a conserved catalytic center, LPMOs show large sequence variation (10,11).…”

Genomics Review of Holocellulose Deconstruction by Aspergilli

“…Thus, we considered only GH12 and GH74 XEGs from aspergilli, due to the lack of characterized gene models for the GH5, GH16, and GH44 families. Furthermore, XEGs from these families were not identified in secretomes of aspergilli growing on biomass (10,14,203,204). Table 9 shows that aspergilli contain one or no GH74 xyloglucanases but several GH12 enzymes.…”

“…However, not all fungi are alike; some fungi, such as Trichoderma reesei and Aspergillus niger, employ predominantly a classical acid catalysis hydrolytic model of degrading plant cell wall polymers, while others, such as Myceliophthora thermophila (11,12) and Phanerochaete chrysosporium (13,14), appear to take advantage of an oxidative route of breaking down glycoside bonds. Even though some fungi predominantly hydrolyze biomass while others employ an oxidative mechanism, most fungi contain a mixed set of hydrolases and oxidases.…”

The Confounding Effects of Particle Size and Substrate Bulk Density on Phanerochaete chrysosporium Pretreatment of Panicum virgatum

“…To our knowledge, 10.16 cm particle sizes have not been tested in biological pretreatment prior to this study Li 2010, 2011;Liong et al 2012;Ray et al 2012;Liu et al 2015). We selected this particle size because this represents a lower limit in particle size practical for large-scale baling.…”

“…The majority of biological pretreatment studies have been conducted on ground lignocelluloses, typically with particle sizes between 1 mm and 2 cm Li 2010, 2011;Liong et al 2012;Ray et al 2012;Liu et al 2015). Decreases in particle size have been shown to correlate with increases in glucose and xylose amounts released upon saccharification when 5-, 10-, and 15-mm corn stover particles were pretreated with Ceriporiopsis subvermispora for 18 d at 28 °C and 75% moisture content (Wan and Li 2010) and enzymatically hydrolyzed.…”