Using organosolv pretreatment with acid wastewater for enhanced fermentable sugar and ethanol production from rubberwood waste. (October 2022) - Nunui, Khanitta
Abstract: The intensive utilization of water in the pretreatment of substrates for lignocellulosic ethanol production negatively impacts its economic feasibility. This study aimed to develop a method of pretreatment using acid wastewater to enhance the conversion of rubberwood waste into fermentable sugar and ethanol. The water was replaced with acid wastewater in hydrothermal pretreatments with and without alkaline post-treatment, and organosolv pretreatment (wastewater:ethanol 50:50). The organosolv pretreatment at 190 °C maximized the fermentable sugar concentration (43.60 g/L) and yield (301.0 ± 13.3 kg/ton rubberwood waste) because of partial delignification and physical redistribution of the rubberwood waste matrix. It also demonstrated markedly better reduction of water utilization, wastewater generation, and energy consumption than other pretreatments. In addition, the hydrolysate derived from the organosolv pretreatment was chosen for ethanol production. Saccharomyces cerevisiae showed better ethanol conversion rate than Kluyveromyces marxianus when the hydrolysate predominantly contained glucose, resulting in an ethanol production of 0.14 g/g rubberwood waste. The pretreatment and fermentation were effective and exhibited the potential to guide lignocellulosic ethanol production in collaboration with latex factories (acid wastewater sources) in future practical applications. Graphical abstract: Image 1 Highlights: Rubberwood waste was feedstock for ethanol production. Acid wastewater can replace water in pretreatment process. Organosolv with acid wastewater effectively enhanced enzymatic hydrolysis. Organosolv demonstrated the lowest water and energy consumption. Saccharomyces cerevisiae achieved the highest ethanol yield.