Biotransformation of rice and sunflower side-streams by monosporic strains of Pleurotus sapidus in a biorefinery approach

BIDEGAIN M.A.; FERNÁNDEZ-LAHORE M; POSTEMSKY P.; OMARINI A.

Pavia

Workshop; Enzymes, biocatalysis and chemical biology: The new frontiers; 2018

EMBO

The application of white-rot fungi solid-state fermentation (SSF) of lignocellulosic biomass is enzyme-related bioprocess conceived as a sustainable way to deal with significant amounts of residues. Its advantages are a low environmental impact, a simple increase of scale and reasonable use of water. This study applies an innovative source of mycelia to increase the value of rice and sunflower discarded biomass. It consisted of the in vitro selection of monosporic strains (Mk) of Pleurotus sapidus able to degrade efficiently xenobiotic compounds. Afterward, selected Mks were studied for their performance to grow and produce laccase and peroxidase under laboratory and in pilot-scale experiments. P. sapidus Dk3174 was used as a source of spores. Isolation and selection of Mks were done by exposing spores to grow in RBBR enriched media. Qualitative oxidoreductase assay on plates was used to reveal enzyme traits and detect the best phenolic oxidizing strains. In vitro selection of 15 Mks growing on rice and sunflower side-streams evaluated: Mycelium growth traits and enzyme profile activity. Scale up the SSF compared enzyme traits in either MK6 vs. Dk3174 and Pasteurization vs. Sterilization decontamination treatments. As results, viable Mks were obtained from fructifications of Dk3174. Degradation of RBBR was used to identify those Mks with greater ligninolytic potential. Further selection was done according to the in vitro growth and enzymatic performance in media with 39% of rice or sunflower side-streams. Pilot-scale studies revealed that sterilized/pasteurized substrates employing the MK6 strain produced different enzymes titers and were comparable with the Dk strain. To conclude, Mk showed high variability of RBBR degradation, growth rate, biomass, and enzymes production. Mk6 was selected to perform enzyme production by scale-up the SSF. Laccase was the main responsible for the biomass degradation. SSF with Mks provided an interesting tool to produce high-value metabolites (enzymes) using a low-cost raw material under the concept of Biorefinery. It should be expected that the evolution of these technologies will collaborate in regional-based bioeconomies at the time that prosecutes a valorization of cereal and grains side-streams.