Sequential detoxification of oil palm fronds hydrolysate with coconut shell activated charcoal and pH controlled in bioreactor for xylitol production

Abstract

Acid hydrolysis pre-treatment on biomass produces furan derivatives, phenolics, and organic acids, which are harmful to the fermenting microorganisms. Removal of inhibitor compounds from the hydrolysate using coconut shell activated charcoal (CSAC) adsorption is essential to improve the quality of detoxified hydrolysate as a feedstock for xylitol production. This study investigated adsorption parameters of different pH (pH 1–7), temperature (17.5–92.5 °C), CSAC-to-hydrolysate loading (0.5–9.5% (w/v)) and contact time (30–142.5 min) using a central composite design (CCD) to evaluate the interactive effect of the adsorption process parameters on response variables. Under optimal adsorption process (pH 2.5, 55.6 °C, 5.3% (w/v) and 74 min), the results demonstrated loss of 10.4% sugar and 12.8 % of detoxified hydrolysate volume with 79.9% of furfural removal. Inhibition by acetic acid could be alleviated by pH control in bioreactor since the concentration of acetic acid was decreased by up to 73.7% at the end of OPF hydrolysate fermentation. The fermentability test using detoxified OPF hydrolysate by Kluyveromyces marxianus ATCC 36907 demonstrated 78% higher xylitol production compared to non-detoxified OPF hydrolysate. This finding corroborates that this sequential detoxification is a promising method to enhance the xylitol production using OPF hydrolysate.