Increased Content of Free Phenolic Compounds and Antioxidant Activity of Grape Pomace Cultivated with Three Different β-glucosidase Fungi Producers

In this research, we tried to recover the antioxidant activities of grape pomace by means of using solid-state cultivation (SSC) of Aspergillus niger BLAn1, Phanerochaete chrysosporium BLPc1, and Penicillium sp. BLPen1, three GRAS strains of fungi. We measured the enzymatic activities of β-glucosidase, responsible for liberating the aglycone forms of the phenolic compounds, as well as their total content. The highest β-glucosidase activities were approximately 17.2, 8.3, and 13.5 U · g-1 pomace for the 3 strains, respectively. The enzyme activity was considerably reduced with moisture-saturated air injection in the system. The total phenolic content obtained were 21.15, 12.13, and 10.08 mg GAE (Acid galic equivalent) · g-1 pomace, whereas the highest antioxidant activities released were 16.30, 11.35, and 10.57 mmol TEAC (Trolox equivalent antioxidant capacity) · g-1 pomace (by DPPH assay), and 158.61, 104.68, and 102.55 mmol TEAC · g-1 pomace (by ABTS assay), for BLAn1, BLPc1, and BLPen1, respectively. These results suggest that the enzyme hydrolysis of phenolic glycosides leads to increased concentrations of free phenolic compounds, enhancing radical- scavenging potential of pomace.