Enhanced enzymatic hydrolysis of pine wilt disease-damaged wood by torrefaction

Pines occur widely on approximately 1,507,118 ha of land representing 23.5% of Korea’s forest area and 15.1% of the country’s land mass. The serious losses from pine wilt disease, reported in Busan in 1988, are a serious threat to Korea’s pine forests.

In this study, we evaluated the potential of pine wilt disease-damaged wood as a biomass feedstock for the production of bioethanol. Torrefaction pretreatment was used to facilitate the conversion of pine wilt disease damaged-wood into fermentable sugar (glucose). Non-damaged wood (Pinus densiflora) and pine wilt disease-damaged wood were torrefied under different conditions (severity log Ro, 3.64 - 4.82), namely 200 - 240 °C (reaction temperatures) for 5 - 10 min (residence time), grinded and then used as a substrate in hydrolysis experiments. The bioconversion was performed at flask-scale using a mixture of cellulase and β-glucosidase enzymes.

The non-damaged wood and pine wilt disease-damaged wood exhibited different chemical compositions and properties. Substrate properties such as ratio of cellulose, hemicellulose, lignin were correlated against the torrefaction pretreatment and enzyme hydrolysis. During torrefaction pretreatment, the cellulose, hemicellulose, and lignin contents in pine wilt disease-damaged wood changed rapidly compared to those in non-damaged wood. The maximum glucose yield (67.8%) was obtained after enzymatic hydrolysis for 96 h of pine wilt disease-damaged wood (severity log Ro, 4.23). Pine wilt disease-damaged wood is a potentially useful biomass resource for the production of biofuels.