Pretreatment of Laminaria japonica for bioethanol production with extremely low acid concentration

The conversion of cellulose hydrolysis was investigated in batch reactors from brown macro-algae under extremely low acid (ELA) pretreatment conditions. The brown macro-algae of Laminaria japonica were conducted for increasing glucan content as an aqua-biomass feedstock. The investigated ELA pretreatment conditions in this study were as follows; the reaction temperature of 150–180 °C, the reaction time of 5–20 min, and sulfuric acid concentrations of 0.02–0.14%. The maximum glucan content of 29.09%, which was four-fold higher than that of the raw L. japonica was obtained after the ELA pretreatment under the optimal condition with sulfuric acid of 0.06% at the temperature of 170 °C for 15 min. In addition, glucan content in solid residue, solid remaining, and the amount of decomposed products in hydrolyzate through ELA pretreatment of L. japonica were compared with those of hot water treatment. Significant enhancement on glucan fraction and enzymatic digestibility of the pretreated L. japonica could be achieved through the ELA pretreatment.