By-products from Fungal Pretreatment of Corn Stalks Enhance Saccharification to Ethanol-fermentable Sugars

The removal of lignin by pretreatment of lignocellulosic biomass is the first phase in the production of cellulose-ethanol. This usually requires extreme use of heat and chemicals, and many of these extreme processes generate toxic/inhibitory compounds. Recently, the use of biological pretreatment using lignin-degrading fungi (usually white-rot fungi) is regaining interest as a milder, less toxic and less-costly pretreatment alternative. There are also indications that by-products produced from fungal pretreatment could enhance the second step of cellulose-ethanol production (the saccharification step, or the conversion of carbohydrates in the pretreated biomass to ethanol-fermentable sugars).

Researchers from Huazhong University of Science and Technology (Wuhan, China) report the pretreatment of corn stalk with a fungus, called Irpex lacteus, and found that its by-products stimulate saccharification. The pretreated biomass samples were exposed to water extracts containing by-products of fungal pretreatment, in combination with commercial saccharification enzymes (cellulases). The study showed that Irpex lacteus can be a promising white-rot fungus for lignocellulosic biomass pretreatment. About 82 percent of glucan hydrolysis yield was obtained after pretreatment. The results also showed that the saccharification efficiency of commercial cellulose preparations was higher when extracts of fungal pretreatment were added to the biomass. The reducing sugar yield was higher by 31 percent. The full results are published in the open-access journal, Biotechnology for Biofuels.