Effects of pretreatment methods on sugar conversion from bark-containing biomass and its application for green chemical production

Pretreatment of lignocellulosic biomass for bio-fuel production produces a large amount of fermentable sugars and degradation products. The pretreatment method significantly affects a characterization of conversion behavior of sugars and yield of degradation products during pretreatment. Therefore, application of sugars as green chemicals (arabinitol, furfural, itaconic acid, levulinic acid, and xylitol) or additional fermentable sugars for bio-fuel production depends on the pretreatment method and its conditions. The main objectives of this study are to investigate effective pretreatment method for obtaining fermentable sugars (in liquid fraction) from bark-containing biomass, and to suggest a possibility for advanced conversion process using fermentable sugars.

Small diameter log of mongolian oak (Quercus mongolica) including bark was ground, sieved through 40-mesh screens, and used in this study. The pretreatment of mongolian oak (glucan: 47.8%, xylan: 17.2%, arabinan: 1.7%, galactan: 1.7%, mannan: 1.4%) was conducted using autohydrolysis, dilute acid (DA), and sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL). After pretreatment, sugars and degradation products in the liquid fraction were analyzed by high performance liquid chromatography (HPLC) or gas chromatography (GC). As a result, total sugar (mainly xylose) and degradation product contents in the liquid fraction were higher by DA (>20%) than by others with comparatively mild conditions (<150°C). On the other hand, SPORL showed a low level of degradation product content (<0.2%). Based on these results, different second steps (enzymatic hydrolysis or chemical treatment) were applied to each sugar for green chemical production.