BACKGROUND: This study investigated the effect of surfactants on wheat straw biodegradation and the growth-associated generation of exo- and endo-phenolic compounds (EPC and IPC) and antioxidant activity expression by liquid-cultured Inonotus obliquus, an edible and medicinal mushroom, also known as a white rot fungus. Changes in the chemical composition and multiscale structure of wheat straw, in the production and activity of EPC and IPC and in individual flavonoids were analyzed. RESULTS: Fungal pretreatment decreased significantly the contents of all lignocellulose components, increased and enlarged substrate porosity and caused changes in the structure of wheat straw with the aid of Triton X-100. A gradual increase in EPC and IPC production was observed up to 6.4- and 1.5-fold for 9 days. The EPC obtained on day 9 showed the highest antioxidant activity (IC50 of 30.96 mg L-1 ) against 2,2-diphenyl-1-picrylhydrazyl radicals. High-performance liquid chromatographic results indicated the presence of high amounts of epicatechin-3-gallate (ECG; (374.9 mg g-1 ) and epigallocatechin-3-gallate (EGCG; 447.2 mg g-1 ) in the EPC; other polyphenols were also enhanced but to a lesser extent. Surfactant supplementation was effective in enhancing flavonoid production and in increasing antioxidant activity in EPC. CONCLUSIONS: The results indicated enhanced accumulation of phenolic compounds, particularly ECG and EGCG in Inonotus obliquus via biodegradation and bioconversion of lignocellulose residues. They also indicated enhancement in the production of several flavonoids and also an increase in antioxidant activity in the product by a surfactant-treated process, which may be a useful way of exploiting underused lignocellulosic residues to various high-added-value functional ingredients.
BACKGROUND: This study investigated the effect of surfactants on wheat straw biodegradation and the growth-associated generation of exo- and endo-phenolic compounds (EPC and IPC) and antioxidant activity expression by liquid-cultured Inonotus obliquus, an edible and medicinal mushroom, also known as a white rot fungus. Changes in the chemical composition and multiscale structure of wheat straw, in the production and activity of EPC and IPC and in individual flavonoids were analyzed. RESULTS: Fungal pretreatment decreased significantly the contents of all lignocellulose components, increased and enlarged substrate porosity and caused changes in the structure of wheat straw with the aid of Triton X-100. A gradual increase in EPC and IPC production was observed up to 6.4- and 1.5-fold for 9 days. The EPC obtained on day 9 showed the highest antioxidant activity (IC50 of 30.96 mg L-1 ) against 2,2-diphenyl-1-picrylhydrazyl radicals. High-performance liquid chromatographic results indicated the presence of high amounts of epicatechin-3-gallate (ECG; (374.9 mg g-1 ) and epigallocatechin-3-gallate (EGCG; 447.2 mg g-1 ) in the EPC; other polyphenols were also enhanced but to a lesser extent. Surfactant supplementation was effective in enhancing flavonoid production and in increasing antioxidant activity in EPC. CONCLUSIONS: The results indicated enhanced accumulation of phenolic compounds, particularly ECG and EGCG in Inonotus obliquus via biodegradation and bioconversion of lignocellulose residues. They also indicated enhancement in the production of several flavonoids and also an increase in antioxidant activity in the product by a surfactant-treated process, which may be a useful way of exploiting underused lignocellulosic residues to various high-added-value functional ingredients.