Investigation of crop straw for edible and medicinal fungi cultivation: Assessment of lignocellulose preprocessing and spent substrate biofuel properties

Abstract

Pretreatment with white-rot fungi has advantages of low inputs of energy and chemicals for reducing the recalcitrance of woody biomass for cellulosic ethanol production. This study investigated the effects of substrates ranging from wood to wheat straw on edible and medicinal fungi production, lignocellulose degradation, cellulose saccharification and ethanolic fermentation of the produced hydrolysates. Shiitake cultivation resulted in the most substantial degradation of lignin and xylan. Reishi produced a selective degradation pattern in terms of preferential xylan removal. Oyster had poor performance in lignocellulose degradation. Shiitake and reishi had high reactivity of S-lignin. The strong recalcitrance of >10 % wheat straw addition for mushroom cultivation might be attributed to the low S:G ratio of the substrates. Compared with the substrate comprising a single hardwood, 10 % wheat straw addition optimised the integration process, resulting in a generally comparable fruiting body yield and higher lignocellulose degradation. The shiitake-based and reishi-based spent mushroom substrates (SMSs) contained ∼21 % glucan, which released 84.4 % and 33.5 % of potentially achievable glucose upon enzymatic saccharification, respectively. The SMS hydrolysates ensured ethanol yields corresponding to 78.0 %–83.2 % of the theoretical value in fermentation. The lignocellulose degradation–derived by-products following the fungal pretreatment showed a notable difference compared with thermochemical methods and might cause inhibitory effects on yeast. This study provides valuable insights into the cause of crop straws’s inhibition of white-rot fungi production and reveals the potential of fungal pretreatment as a biorefinery approach producing food and biofuel.