The objectives of this study were to investigate the medicinal mushroom Inonotus obliquus on the production of polysaccharides and changes of extracellular lignocellulolytic enzymes during submerged fermentation using alkali-treated birch sawdust as substrate. Meanwhile, in order to explore the degradation mode of lignocellulose in alkali-treated birch sawdust, degradation analysis of three components of lignocellulose was carried out. The fungus process in alkali-treated birch sawdust medium resulted in a higher degradation rate of cellulose, hemicellulose, and lignin of 39.24%, 51.00% and 31.3% after 11 days of submerged fermentation by the mycelium of I. obliquus, respectively. Maximal polysaccharide production and α-glucosidase inhibition rate determined in the alkali-treated birch sawdust medium were 6.93 mg/mL and 55.80%, while they were 4.98 mg/mL and 27.89% in the control. Moreover, high activities of laccase (51.95 IU/mL), CMCase (1.35 IU/mL), filter paper activity (0.50 IU/mL) and β-glucosidase (0.55 IU/mL) were observed in alkali-treated birch sawdust medium, respectively. The results demonstrated that the addition of alkali-treated birch sawdust could promote the yield and α-glucosidase inhibition activity of polysaccharides and induce the production of cellulase and xylanase, indicating that alkali pretreatment was conducive to utilization of birch sawdust by I. obliquus.
Keywords: Alkali treatment; Birch sawdust; Inonotus obliquus; Lignocellulolytic enzymes; Polysaccharides.
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