Agricultural Coconut Cultivation Wastes as Feedstock for Lignocellulosic Ethanol Production by Kluyveromyces marxianus

This work presents a study using coconut cultivation wastes as carbon sources to produce lignocellulosic ethanol, such as green coconut shell (GCS), coconut-tree leaflet (CLL) and coconut-tree leaf stalk (CLS). The biomasses were submitted to hydrothermal (HPT) and acidic (APT) pretreatment. Enzymatic hydrolysis was performed using Cellic® Ctec2 supplemented with 10% Cellic® Htec, mainly based on the identification of glucose and xylose. It was found that enzymatic hydrolysis after HPT promoted better results when compared to APT. The glucose concentrations obtained for the biomasses submitted to the HPT were: 31.85 g/L for the GCS, 21.31 g/L for the CLL and 45.39 g/L for the CLS. For xylose, the higher concentration obtained was 7.93 g/L. During the fermentation step applying the yeast Kluyveromyces marxianus , ethanol concentrations (g/L) from HPT and APT hydrolyzed liquors were: 8.83 and 9.71 g/L for GCS, 10.26 and 7.01 g/L for CLL and 12.99 and 7.44 g/L for CLS, respectively. This study identified the energy potential of coconut residues in the production of biofuels, specifically ethanol, from K. marxianus , species which is little explored commercially and able to ferment glucose and xylose. Graphic Abstract