The promoting effect of byproducts from Irpex lacteus on subsequent enzymatic hydrolysis of bio-pretreated cornstalks

Background: Irpex lacteus, a versatile lignin-degrading fungus with various extracellular enzymes, has been widely used for biological pretreatment. However, most studies have focused on the change of substrate structure after biological pretreatment, and the effect of these changes on the enzymatic hydrolysis, but the effect of byproducts from biological pretreatment process on subsequent enzymatic hydrolysis is not well understood. Methods: We developed a biological pretreatment process with I. lacteus that can produce stimulatory byproducts that enhance the enzymatic hydrolysis of cornstalks. Results: The maximum hydrolysis yield of glucan (82%) was obtained after pretreatment for 28 days. The maximum reducing sugar yield decreased from 313.5 to 200.1 mg/g raw cornstalks after water-soluble byproducts of biological pretreatment were removed from pretreated cornstalks. The effect of byproducts on enzymatic hydrolysis was also investigated. We found that the hydrolysis efficiency of commercial cellulase preparation on cornstalks could be improved by water extracts from bio-pretreated cornstalks with hydrolytic enzyme activity and iron-reducing activity. Conclusion: The key finding suggested that byproducts from biological pretreatment play important roles in enhancing downstream hydrolysis, which might be attributable to hydrolytic enzymes and iron-reducing compounds produced by I. lacteus.