Dielectric barrier discharge plasma on water to decrease recalcitrance of lignocellulosic biomass

We have been studied a new pretreatment method that use Dielectric Barrier Discharge (DBD) plasma formed by water to decrease recalcitrance of enzymatic hydrolysis of lignocellulosic biomass. DBD plasma on water pretreatment produces a large volume of non-thermal plasma at atmospheric pressure allowed to operate at high alternating voltages without the occurrence of plasma arcs providing energy transfer in the form of micro-discharges distributed over the entire reaction volume. Prototype reactor was constituted of a vessel with up to 10% w/v of biomass in water. Plasma discharge was achieved with electrodes positioned near the water surface, powered by an electrical source of 14 kV, 50 hz, and 30 mA. The Influence of pretreatment time and pH were studied using sugarcane bagasse with following composition: cellulose, 43.1%; hemicelluloses, 28.7%; lignin, 23.3 % (w/w). After 2h plasma pretreatment time, pH 12 and 60^oC the biomass lignin content went down to 9.7% and hemicellulose to 16.1% (w/w). Blank experiments were run out in pH 12; in 2h and 60^oC without plasma discharge and did not lead to appreciable difference in biomass composition comparing to the raw sugarcane bagasse. Scanning Electronic Microscopy image demonstrated a cleaning effect on surface of plasma samples. Enzymatic hydrolysis (10 FPU/g biomass; 10% w/v; pH 4.8; 72h) of plasma pretreated material lead respectively to 3 and 6 folds increment on glucose yield compared to the blank samples and the raw sugarcane bagasse. It was concluded that DSB liquid plasma is a potential lignocellulosic biomass pretreatment method.