Development of a sustainable bioprocess based on green technologies for xylitol production from corn cob

Abstract

In this work, a sustainable and environmental friendly strategy for the biotechnological production of xylitol was proposed and optimized. For this purpose, corn cob was hydrothermally pretreated at high solid loadings (25%) for an efficient solubilization of xylan in hemicellulose derived compounds, xylooligosaccharides and xylose. Xylose enriched streams were obtained from the enzymatic saccharification of the whole slurry (solid and liquid fraction) resulting from the autohydrolysis pretreatment. The xylitol production in a simultaneous saccharification and fermentation (SSF) process, by the recombinant Saccharomyces cerevisiae PE-2-GRE3 strain, was optimized using different enzyme and substrate (pretreated corn cob solid) loadings by an experimental design. This study demonstrated a significant effect of substrate loading on the production process achieving a maximal concentration of 47 g/L with 6.7 % of pretreated corn cob and 24 FPU/g of enzyme loading, with partial detoxification of the hydrolysate. Furthermore, the 1.42-fold increase in xylitol titer and 1.56-fold increase in productivity achieved in a SSF using an acetic acid free-hydrolysate evidenced the negative effect of acetic acid on the yeast-based xylitol production process. The combination of these green technologies and the optimization of the proposed strategy enhanced the overall xylitol production through the valorization of corn cob.

Production of xylitol by Saccharomyces cerevisiae using waste xylose mother liquor and corncob residues

“…Our data showed that although DX7 had much stronger XR activity than X3, xylitol production capacity of X3 was much greater than that of DX7 in WXML fermentation. We suspect the cause is based on their different metabolic characteristics, particularly the accumulation of acetate (Figs 4 and 5), which is toxic to yeasts (Semchyshyn et al ., 2011; Orlandi et al ., 2013) and shows negative effect on the yeast‐based xylitol production process (Baptista et al ., 2020). The acetate produced by DX7 kept accumulating after 36 h of fermentation, while the acetate produced by X3 did not accumulate and actually decreased after 36 h (Fig.…”

“…glucose or glycerol) because they are cheaper than xylose is also a common strategy to achieve high yields of xylitol with low production cost (Dasgupta et al ., 2017; Hua et al ., 2019; Park et al ., 2019; Xu et al ., 2019). Recently, the SSF process was also used in xylitol production from corn cob whole slurry (Baptista et al ., 2018; Baptista et al ., 2020). The high yield was gotten, while the final xylitol titer was limited by the xylose concentration in the substrate.…”

“…The final optimized strain was then tested for successful growth and xylitol production by fed‐batch fermentation using WXML as the substrate and glucose as the co‐substrate. Additionally, we applied the simultaneous saccharification and fermentation (SSF) method, a process often used in the fermentation of cellulosic ethanol (Loaces et al ., 2017) and recently used in xylitol production (Baptista et al ., 2018; Baptista et al ., 2020), to use DCCR and cellulase to produce the glucose in one system instead of separately adding glucose as a co‐substrate in the xylitol fermentation process. Our work demonstrates a promising strategy of using wastes and by‐products to increase xylitol production while decreasing the pollution resulting from the commercial production of xylitol.…”

Rational engineering of industrial S. cerevisiae: towards xylitol production from sugarcane bagasse

“…One of the challenges of using sugarcane hydrolysate in whole-cell fermentation resides in the inhibitory nature of several pretreatment by-products. While such hemicellulosic feedstock has been tested for xylitol production using yeast Candida guilliermondii [53,54], approaches using recombinant S. cerevisiae have been limited to either corn cob [15,17,18,55], rice straw or woody biomass [16,56] as natural xylose sources. Using sugarcane biomass to produce high added-value chemicals with S. cerevisiae is a prospect for future biorefineries [57], and our experiments join this discussion.…”

Xylitol: Bioproduction and Applications-A Review

“…Here, the biomass is treated at high pressure and temperature of around 200 • C due to which the acetyl groups in the hemicellulose get hydrolyzed to release acids that break bonds between the carbohydrates and lignin. Baptista et al (2018Baptista et al ( , 2020) have used the auto-hydrolysis method to pretreat corncob and have reported the highest titer of xylitol production using recombinant Saccharomyces cerevisiae.…”