Simultaneous decolourisation and biohydrogen production from xylose by Klebsiella oxytoca GS-4-08 in presence of azo dyes with sulfonate and carboxyl groups

Biohydrogen production from the pulp and paper effluent containing rich lignocellulosic material could be achieved by the fermentation process. Xylose, an important hemicellulose hydrolysis product, is used less efficiently as a substrate for biohydrogen production. Moreover, azo dyes are usually added to fabricate anti-counterfeiting paper, which further increases the complexity of wastewater. This study is the first paper to report that xylose could serve as the sole carbon source for a pure culture-Klebsiella oxytoca GS-4-08 to achieve simultaneous decolourisation and biohydrogen production. With 2 g l(-1) of xylose as the substrate, a maximum xylose utilisation rate (URXyl) and a hydrogen molar yield (HMY) were obtained as 93.99% and 0.259 mol H2 mol(-1) xylose, respectively. Biohydrogen kinetics and e(-) equiv balance calculations indicated that MR penetrates and intracellularly inhibits on both pentose phosphate pathway and pyruvate fermentation pathway, while MO was independent of the glycolysis and biohydrogen pathway. The data demonstrate that biohydrogen pathways in the presence of azo dyes with sulfonate and carboxyl groups were different, but the azo dyes could be completely reduced during the biohydrogen production period whether with the presence of MO or MR. The feasibility of hydrogen production from industrial pulp and paper effluent by the strain was also proved if the xylose is sufficient, and not affected by toxic substances which usually exists in such wastewater except for chlorophenol. This study offers a promising energy-recycling strategy for treating pulp and paper wastewaters, especially for those containing azo dyes. The pulp and paper industry is a major industry in many developing countries and the global market of pulp and paper wastewater treatment is expected to increase by 60% between 2012 and 2020. Such wastewater contains large amount of refractory contaminants, such as lignin, whose reclamation is considered economic crucial and environmentally friendly. Furthermore, azo dyes are usually added in order to fabricate anti-counterfeiting paper, which further increases the complexity of the pulp and paper wastewater. The authors concluded that this work may offer a better understanding of biohydrogen production from xylose in the presence of azo dyes, and provide a promising energy-recycling method for treating pulp and paper wastewater, especially for those containing azo dyes.

Authors: Yu L, Cao MY, Wang PT, Wang S, Yue YR, Yuan WD, Qiao WC, Wang F, Song X. ;Full Source: Applied Environmental Microbiology. 2017 Mar 10. pii: AEM.00508-17. doi: 10.1128/AEM.00508-17. [Epub ahead of print] ;