Optimization of Activated Carbon Adsorption for Detoxification of Sugarcane Bagasse Hydrolysate by Response Surface Methodology to Enhance Ethanol Production

Abstract

Lignocellulosic biomass has significant potential as a renewable resource for biofuel production. Bioethanol is a widely used biofuel derived from agricultural residues such as cassava, rice straw, sugarcane, and sorghum. In this study, sugarcane bagasse was used as the raw material for ethanol production by Pichia stipitis TISTR5806. The objective was to examine the effect of activated carbon in removing inhibitory compounds from hydrolysate to enhance ethanol fermentation. Sugarcane bagasse was pretreated with 2.0% v/v diluted sulfuric acid at 121°C for 60 minutes to obtain hydrolysate. Acid hydrolysis generates monomeric sugars and inhibitory compounds, including furfural, 5-hydroxymethylfurfural (5-HMF), phenolics, and organic acids. To mitigate the inhibitory effects and improve ethanol production, this study employed activated carbon for compound removal. A central composite design was used to determine the optimal detoxification conditions for activated carbon, varying its concentration (1–5% w/v), reaction temperature (30–60°C), and reaction time (20–60 minutes). The optimal conditions were identified as 3.0% w/v activated carbon, a reaction temperature of 45°C, and a reaction time of 40 minutes. Under these conditions, activated carbon removed 23.93% of total furans and 61.72% of phenolics. The ethanol yield from the untreated hydrolysate was 0.21 gproduct/gsubstrate, corresponding to a theoretical yield of 42.44%, with an ethanol production rate of 0.09 g/L·h. In contrast, the detoxified hydrolysate yielded 0.26 gproduct/gsubstrate, achieving a theoretical yield of 51.30% and an ethanol production rate of 0.28 g/L·h. These results indicate that sugarcane bagasse is a promising substrate for ethanol production and that activated carbon effectively removes inhibitory compounds from hydrolysate, thereby enhancing fermentation efficiency.