An improvement in fermentability of acid-hydrolysed hemicellulose from kenaf stem for xylitol production

Abstract

In recent years, there has been a growing interest in the use of agricultural biomass for fermentation purposes; however, efficient strategies to counter lignocellulose inhibition are warranted to enhance xylitol production performance. Dilute-acid hydrolysis has been studied to selectively release a significant portion of xylose from hemicellulose, while leaving cellulose and lignin intact. The formation of inhibitory compounds, however, could jeopardise the overall performance during fermentation to produce xylitol. In this study, the fermentability of nitric acid-hydrolysed kenaf stem was substantially improved, through either adaptive evolution of the recombinant Escherichia coli BL21 (DE3) or removal of fermentation inhibitors by detoxification with activated carbon. Both methods were compared to evaluate the superiority in fermentative performance. In the fermentation with detoxified hemicellulosic hydrolysate, the non-adapted strain produced the highest xylitol concentration of up to 6.8 g/L, with 61.5% xylose consumption. The yields of xylitol production involving detoxification were successfully enhanced by 22.6% and by 35.7% compared to those involving adaptive evolution and raw hydrolysate, respectively. The results reported herein suggest that the utilization of detoxified kenaf stem hydrolysate could be advantageous.

Short-Term Adaptation Strategy Improved Xylitol Production by Candida Guilliermondii on Sugarcane Bagasse Hemicellulosic Hydrolysate

“…An improvement in xylitol production by cell adaptation was also observed by Shah et al (2020) [33].…”

Short-term Adaptation Strategy Improved Xylitol Production by Candida guilliermondii on Sugarcane Bagasse Hemicellulosic Hydrolysate

“…After 24 h cultivation more than 80% of the xylose had been consumed by adapted recombinant S. cerevisiae, while non-adapted cells consumed only 45%. In another study, an increase in the total xylose consumption (from 26.3 to 62.7 %), was also observed for Escherichia coli adapted in increasing concentrations of kenaf hydrolysate [33].…”

“…Similar behavior was reported bySene et al (2001) [36] when adapting C. guilliermondii to increasing concentration factors of sugarcane bagasse hemicellulosic hydrolysate.An improvement in xylitol production by cell adaptation was also observed byShah et al (2020) [33].These authors carried out the adaptation of a recombinant strain of E. coli in increasing concentrations of kenaf hemicellulosic hydrolysate, and consequently of toxic compounds, observing at the end of the cultivation a two-fold increase in xylitol production and an improvement of 10.7 and 100% in the xylitol yield and volumetric productivity, respectively Sene et al (2001). [36] observed a 34% increase in xylitol production by C. guilliermondii adapted to sugarcane bagasse hemicellulosic hydrolysate four-fold concentrated in comparison to non-concentrated hydrolysate Wang et al (2011).…”

Xylitol: Bioproduction and Applications-A Review

“…Industrially, acid hydrolysis, particularly dilute-acid hydrolysis, is the most commonly employed method owing to its efficiency in hydrolyzing hemicellulose at a fast rate at less cost (Martin et al, 2013). Moraes et al (2020) have obtained 99% extraction of xylose by pretreating the biomass with 1% sulphuric acid at 120 • C. The use of nitric acid hydrolysis has been found to improve xylose extraction (Dalli et al, 2017b;Manaf et al, 2018;Shah et al, 2020). Acid pretreatment releases monomeric sugars from the hemicellulose thereby eliminating the need for a further hydrolysis step.…”