Effect of Fungal Solid-State Fermentation on the Profile of Phenolic Compounds and on the Nutritional Properties of Grape Pomace

Abstract

Grape pomace (GP) is considered a natural source of bioactive compounds. To improve the ex-tractability of bioactive compounds, in this work GP was biologically treated for 15 days with the white-rot fungus Trametes versicolor in laboratory jars and a tray bioreactor under solid-state fermentation (SSF) conditions. During SSF, the activity of lignolytic (laccase, manganese peroxi-dase) and hydrolytic (xylanase, cellulase, β-glucosidase and invertase) enzymes was measured, with the activity of laccase (2.66 U/gdb in jars and 0.96 U/gdb in the bioreactor) and xylanase (346.04 U/gdb in jars and 200.65 U/gdb in the bioreactor) being the highest. The effect of the com-plex enzyme system was reflected in the changes in the chemical composition of GP with in-creasing ash, crude protein and free fat content: 28%, 10% and 17% in the laboratory jars and 29%, 11% and 7% in the bioreactor, respectively. In addition, the biological treatment had a positive effect on the extractability of 13 individual phenolic compounds. Therefore, the applied SSF technique represents an effective strategy to improve the profile of phenolic compounds and the nutritional composition of GP, promoting their valorization and opening the door for potential application in the food industry and other sectors.