Mediterranean agro-industrial wastes as valuable substrates for lignocellulolytic enzymes and protein production by solid-state fermentation.

BACKGROUND: Mediterranean agro-food industries (such as wineries, breweries and olive mills) dispose of great amounts of waste. This generates environmental problems, and the waste has a low nutritional value for use as animal feed. In this sense, solid-state fermentation (SSF) can increase the nutritional value of these wastes and simultaneously produce lignocellulolytic enzymes.
RESULTS: All fermented wastes were enriched in protein by the three fungi studied. Aspergillus ibericus was the fungus with the biggest increase of protein, which ranged from 1.4 times to 6.2 times with respect to unfermented wastes. Likewise, A. ibericus achieved the maximum cellulase and xylanase activities. The relationships among substrates composition, fungi used and SSF performance were evaluated by principal components analysis. The high content of cellulose and hemicellulose favoured lignocellulolytic enzymes production, and the phenolics content was negatively correlated with enzymes production and with the increase of protein by SSF. Furthermore, the scanning electron microscopy analysis showed the growth of fungi over solid wastes, the formation of conidiophores and the changes in their structures.
CONCLUSION: The nutritional value of Mediterranean wastes was improved and other value-added products such as lignocellulolytic enzymes were produced in the same process, which could facilitate the efficient reuse of these wastes.