Phytotoxicity reduction of walnut green husk by white-rot fungi under solid-state fermentation

Abstract Phytotoxicity reduction is one of the main aims of reusing walnut green husk (WGH) for cultivation purposes. This study was conducted to evaluate the efficiency of bio-detoxification by selected Trametes and Schizophyllum strains under solid-state fermentation. Ninety-two isolates of filamentous fungi were obtained from forest litter, and nine strains belonging to Trametes and Schizophyllum genus were selected due to their efficient laccase production and rapid growth using WGH and corncob (w/w, 1:1) as the carbon source under solid-state fermentation. Further, enzyme activities and phytotoxicity assays showed that water extract of WGH treated by Trametes strains 120301, 10288, and 10306 showed a vast lignocellulose enzyme system, higher laccase activity (about 620 U/g), and maximal germination rate (100%), compared with 20% germination rate of the untreated extract of WGH. Our results indicated that Trametes strains are suitable for the phytotoxicity reduction of WGH and laccase production, and showed the possible role of laccase in the detoxification of agricultural wastes rich in phenols such as WGH.