Co-elicitation of lignocelluloytic enzymatic activities and metabolites production in an Aspergillus-Streptomyces co-culture during lignocellulose fractionation

Lignocellulose, the most abundant biomass on Earth, is a complex recalcitrant material mainly composed of three fractions: cellulose, hemicelluloses and lignins. In nature, lignocellulose is efficiently degraded for carbon recycling. Lignocellulose degradation involves numerous microorganisms and their secreted enzymes that act in synergy. Even they are efficient, the natural processes for lignocellulose degradation are slow (weeks to months). In this study, the objective was to study the synergism of some microorganisms to achieve efficient and rapid lignocellulose degradation. Wheat bran, an abundant co-product from milling industry, was selected as lignocellulosic biomass. Mono-cultures and co-cultures involving one A.niger strain fungi never sequenced before (DSM 1957) and either one of three different Streptomyces strains were tested in order to investigate the potentiality for efficient lignocellulose degradability. Comparative genomics of the strain Aspergillus niger DSM 1957 revealed that it harboured the maximum of AA, CBM, CE and GH among its closest relative strains. The different co-cultures set-up enriched the metabolic diversity and the lignocellulolytic CAZyme content. Depending on the co-cultures, an over-expression of some enzymatic activities (xylanase, glucosidase, arabinosidase) was observed in the co-cultures compared to the mono-cultures suggesting a specific microbial cross-talk depending on the microbial partner. Moreover, metabolomics for each mono and co-culture was performed and revealed an elicitation of the production of secondary metabolites and the activation of silent biosynthetic cluster genes depending on the microbial co-culture. This opens opportunities for the bioproduction of molecules of interest from wheat bran.