Simultaneous production of lignocellulolytic enzymes and extraction of antioxidant compounds by solid-state fermentation of agro-industrial wastes

Abstract

In recent years, the interest to find alternative extraction methods has increased. Extraction of natural phenolics by enzymes produced during solid-state fermentation (SSF) is a useful and novel technique environmentally friendly. On the other hand, agro-industrial wastes are an excellent source of natural antioxidants as phenolics.The aim of the work was to evaluate the increase of antioxidant compounds extraction from agro-industrial wastes after SSF and to relate it to the production of lignocellulolytic enzymes. Several filamentous fungi were evaluated as candidates to increase the extraction of antioxidant compounds by solid-state fermentation of wineries, olive mill and brewery wastes. Fermented and unfermented agro-industrial wastes were extracted with water and lignocellulolytic enzymes, total phenolic compounds and antioxidant activity were determined in the extract. The maximum xylanase and cellulase activities were achieved by A. ibericus strains using brewer´s spent grain (BSG) as substrate and ranged from 300 to 313 U xylanase/g and 51–62 U cellulase/g. The best producer of β-glucosidase was A. niger CECT2088 using BSG as substrate (94 ± 4 U/g). The results of extraction of phenolic compounds revealed a higher extraction by SSF in olive mill wastes followed by winery wastes. In the same form, the maximum increase of antioxidant activity was achieved by SSF of exhausted olive pomace by Rhizopus oryzae MUM 10.260, increasing 12.9-fold in relation to unfermented waste. In addition, the production of enzymes, the extraction of phenolic compounds and the increase of antioxidant activity were related by principal component analysis. The first component grouped the BSG along with maximum enzymes production, the second component related positively the production of enzymes and the extraction of phenolic compounds and the increase of antioxidant activity.SSF proved to be an innovative environmentally friendly process that can improve the extraction of antioxidant compounds and simultaneously to produce lignocellulolytic enzymes from different agro-industrial wastes.