Alkaline pre-treatment of gelidium latifolium and caulerpa racemosa for bioethanol production

Abstract

Raw material pre-treatment becomes an important step in the bioetanol production from macroalgae. It's help to breakdown sulfated groups and lignin, facilitate the hydrolysis process to increase reducing sugars. Gelidium latifolium and Caulerpa racemosa are red and green algae which used for bioethanol production in this study. The carbohydrate content was 23.81% and 30.54% respectively. The study aims to evaluate the effect of alkaline pre-treatment to the chemical characteristics of macroalgae, productivity of sugar and bioethanol. The alkaline used was sodium hydroxide (NaOH) with a concentration of 0.05 and 0.1 N, soaking time for 3 days at room temperature. From the result, it was known that water and alkaline pre-treatment increased cellulose content for both macroalgae, as well as yield of reducing sugars. The highest reducing sugar for G. latifolium was 5.26% w/v obtained from 0.1 N NaOH pre-treatment. While for C. racemosa it was 7.67% w/v obtained from the one which submerged on water. G. latifolium treated with 0.05 N NaOH has the highest ethanol content of 6.3 ml/L with 21.94% fermentation efficiency and 37.30% substrate efficiency. On the other hand, the highest ethanol production for C. racemosa obtained from water immersion of 7 ml/L with 17.26% fermentation efficiency and 15.41% substrate efficiency.