Fungal Pretreatment Improves Cellulosic Ethanol Yield

A team of Chinese scientists achieved higher cellulosic ethanol yield from biodegradation of poplar wood chips pretreated with white rot fungus compared to non-treated control, reports the journal Biotechnology for Biofuels.

Biological pretreatment with white rot fungi has been recognized as a potential method of enhancing the degradation of lignocellulose feedstock prior to fermentation of released sugar molecules into ethanol. Lignocellulose is a major component of woody biomass used as second generation biofuel feedstock. The lignin polymer strongly intermesh with cellulose, and hemicellulose components of lignocellulose is a tough barrier that prevents access to target sugar during fermentation process. Biological agents like white rot fungi that aid in wood decay process are known to possess natural enzymes capable of opening the complex structure of lignin molecules.

The Chinese scientists pretreated the milled triploid poplar wood with the white rot fungal isolate designated as Trametes velutina D10149 and incubated the mixture for 4 to16 weeks. Ethanol production was measured following simultaneous saccharification and fermentation (SSF) wherein enzymatic breakdown of cellulose and fermentation of sugar into ethanol were run at the same time. While fungal pretreatment did not significantly degrade the lignin, the ethanol yield from SSF was higher (21 to 75 percent) for pretreated samples compared to the untreated control (18 percent). The poplar sample biodegraded for 16 weeks after 24-hour SSF yielded a conversion rate of 34.8 percent. The researchers assumed that the modification of lignin structure during fungal treatment had played a key role in improving cellulose bioconversion rates.