Time-Course Carbohydrate-Active Enzyme Production of Neofusicoccum Parvum and its Enzymatic Hydrolysis Performance on Wheat Straw and Grapevine Canes

The continuing search for more efficient, low-cost enzymes for biomass hydrolysis is a crucial issue in plant biorefining. Due to their ability to secrete a broad set of plant cell-wall degrading enzymes, phytopathogenic wood-colonizing fungi depict a promising source of lignocellulolytic enzymes. However, the use of phytopathogenic fungal enzymes in plant biorefining remains poorly explored. Here, we assessed the capacity of lignocellulolytic enzymes produced by the grapevine trunk pathogen Neofusicoccum parvum in the breakdown of non-pretreated wheat straw (WS) and grapevine canes (GP) after growth on these two substrates.

First, we determined the peak activity time of lignocellulases during 42 days of cultivation. In addition, transcriptomics at late growth stages was performed. Second, we evaluated the performance of secreted enzymes from the WS (WS-S) and GP (GP-S) cultures in hydrolyzing both lignocellulose substrates.

Most of the enzymes reached the maximum activity between 14 and 28 days post-inoculation. Enzyme assays combined with transcriptomics revealed a dynamic enzyme utilization, where (hemi-)cellulases were predominantly produced at early growth stages. Afterward, enzymes acting on more recalcitrant polymers became more prominent. The WS-S released more xylose, arabinose, and total sugars from WS (3.3, 7.4, and 4.9% yields, respectively) than GP-S, although the latter generated more glucose from GP (2.4% yield). The sugar yields produced by N. parvum enzymes, particularly on WS hydrolysis, were comparable with those reported for typical industrial-use fungi, such as Aspergillus and Trichoderma spp.

These findings suggest that N. parvum may be a helpful source of lignocellulolytic enzymes for plant biorefining.

The efficient enzymatic conversion of lignocellulose to fermentable sugars is one of the major bottlenecks in plant biorefining. That has led to a constant search for novel lignocellulolytic enzymes. Plant pathogens represent a rich but little exploited source of cell wall-degrading enzymes. This work shows that lignocellulolytic enzymes from the fungal trunk pathogen Neofusicoccum parvum performed comparatively well in converting non-pretreated wheat straw and grapevine canes into monomeric sugars. Our results suggest that both agricultural residues can be used as a cheap carbon source for producing enzymes of interest for plant biorefining, which may contribute to their valorization, particularly for the less explored grapevine pruning residues. In addition, we described a temporal utilization of lignocellulolytic enzyme in N. parvum.