Abstract
Sugarcane bagasse is an agricultural residue rich in xylose, which may be used as a feedstock for the production of high-value-added chemicals, such as xylonic acid, an organic acid listed as one of the top 30 value-added chemicals on a NREL report. Here, Zymomonas mobilis was engineered for the first time to produce xylonic acid from sugarcane bagasse hydrolysate. Seven coding genes for xylose dehydrogenase (XDH) were tested. The expression of XDH gene from Paraburkholderia xenovorans allowed the highest production of xylonic acid (26.17 ± 0.58 g L−1) from 50 g L−1 xylose in shake flasks, with a productivity of 1.85 ± 0.06 g L−1 h−1 and a yield of 1.04 ± 0.04 gAX/gX. Deletion of the xylose reductase gene further increased the production of xylonic acid to 56.44 ± 1.93 g L−1 from 54.27 ± 0.26 g L−1 xylose in a bioreactor. Strain performance was also evaluated in sugarcane bagasse hydrolysate as a cheap feedstock, which resulted in the production of 11.13 g L−1 xylonic acid from 10 g L−1 xylose. The results show that Z. mobilis may be regarded as a potential platform for the production of organic acids from cheap lignocellulosic biomass in the context of biorefineries.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
When sugarcane bagasse hydrolysate was used as a cheap feedstock, Z. mobilis was able to produce 11.13 g L−1 xylonic acid from 10 g L−1 xylose, showing that this bacterium may be regarded as a potential platform for the production of organic acids from lignocellulosic biomass
To investigate the ability of using lignocellulosic hydrolysate in the xylonic acid production by Z. mobilis, another fermentation was performed using C5 hydrolysate from sugarcane bagasse (8.5 g L−1 glucose, 100 g L−1 xylose, 20 g L−1 acetate, 1 g L−1 5hydroxymetilfurfural and 2 g L−1 furfural), which was added at 10% in defined medium
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. 7.7 g L−1 h−1 [26] were achieved by G. oxydans and P. sacchari, respectively This native production of xylonic acid is possible due to the presence of an alternative xylose oxidation pathway discovered in P. fragi [27]. 5-hydroxymethylfurfural as products of sugar degradation, being acetic acid ubiquitous in this material [40] Given these features, we sought in this work the engineering of Z. mobilis for the production of xylonic acid from sugarcane bagasse hydrolysate as an inexpensive lignocellulosic feedstock. When sugarcane bagasse hydrolysate was used as a cheap feedstock, Z. mobilis was able to produce 11.13 g L−1 xylonic acid from 10 g L−1 xylose, showing that this bacterium may be regarded as a potential platform for the production of organic acids from lignocellulosic biomass
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