Oil palm trunk biomass pretreatment with oxalic acid and its effect on enzymatic digestibility and fermentability

Oil palm trunk biomass (OPTB) is a promising lignocellulosic resource for bioconversion due to its abundant availability, low cost and high carbohydrates content. In the present work, oxalic acid was used to pretreat OPTB under different pretreatment conditions. We maintained the same pretreatment severity value by manipulating the reaction time over a range of oxalic acid concentrations. The impact of oxalic acid pretreatment was evaluated in terms of xylose recovery, enzymatic digestibility as well as fermentability of Actinobacillus succinogenes 130Z for the production of industrially valuable succinic acid. Our findings demonstrated that oxalic acid at 4% (w/v) concentration showed superior effectiveness in solubilising hemicellulose from OPTB, achieving 60.3% xylose recovery. During enzymatic hydrolysis, again, the OPTB pretreated with 4% (w/v) oxalic acid exhibited the highest enzymatic digestibility of 63.4% yielding 39.1 g of sugar per 100 g OPTB. However, it was found that high concentration of oxalic acid (3-4%, w/v) inhibited A. succinogenes 130Z fermentation. The results reported herein suggest that the pretreatment using low oxalic acid (1%, w/v), though requiring longer reaction time, is preferable for an improved succinic acid production from OPTB. (C) 2019 Elsevier Ltd. All rights reserved.