Exploring the natural fungal biodiversity of tropical and temperate forests toward improvement of biomass conversion

Abstract

In this study, natural fungal diversity in wood-decaying species was explored for biomass deconstruction. In 2007 and 2008, fungal isolates were collected in temperate forests mainly from metropolitan France and in tropical forests mainly from French Guiana. We recovered and identified 74 monomorph cultures using morphological and molecular identification tools. Following production of fungal secretomes under inductive conditions, we evaluated the capacity of these fungal strains to potentiate a commercial Trichoderma reesei cellulase cocktail for the release of soluble sugars from biomass. The secretome of 19 isolates led to an improvement in biomass conversion of at least 23%. Of the isolates, the Trametes gibbosa BRFM 952 (Banque de Ressources Fongiques de Marseille) secretome performed best, with 60% improved conversion, a feature that was not universal to the Trametes and related genera. Enzymatic characterization of the T. gibbosa BRFM 952 secretome revealed an unexpected high activity on crystalline cellulose, higher than that of the T. reesei cellulase cocktail. This report highlights the interest in a systematic high-throughput assessment of collected fungal biodiversity to improve the enzymatic conversion of lignocellulosic biomass. It enabled the unbiased identification of new fungal strains issued from biodiversity with high biotechnological potential.

Fig 1

Natural fungal diversity explored. The cladogram was constructed on the basis of ITS sequences, and pictures illustrate the main fungal classes represented.

Fig 2

Species distribution following hydrolysis of biomass. Hydrolysis of biomass was performed with fungal secretomes alone (y axis) and in supplementation with the T. reesei commercial cocktail (x axis). Fungal secretomes were from commercial cocktails (full circles), tropical isolates (open squares), or temperate isolates (open triangles). Names of the best-performing fungi and commercial cocktails are indicated.