Comparison of various organic acids for xylo-oligosaccharide productions in terms of pKa values and combined severity

Rou Cao,Yong Xu,Jianming Guo,Xinlu Liu

doi:10.1186/s13068-021-01919-9

Rou Cao, Yong Xu + Show 2 more

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https://doi.org/10.1186/s13068-021-01919-9

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Abstract

BackgroundMethods to produce XOS have been intensively investigated, including enzymatic hydrolysis, steam explosion, and acid hydrolysis. Acid hydrolysis is currently the most widely used method to produce XOS due to its advantages of fewer processing steps, stronger raw material adaptability, higher yield, and better reproducibility. Especially, organic acids such as acetic acid, formic acid and xylonic acid work better as compared with mineral acids. However, the catalytic mechanism of different organic acids has been little studied. In this paper, four different organic acids, including formic acid, glycolic acid, lactic acid, and acetic acid were selected to compare their hydrolytic effects.ResultsUsing pKa values as the benchmark, the yield of xylo-oligosaccharide (XOS) increased with the increasing value of pKa. The yield of XOS was 37% when hydrolyzed by 5% acetic acid (pKa = 4.75) at 170 ℃ for 20 min. Combined severity (CS), a parameter associated with temperature and reaction time was proposed, was proposed to evaluate the hydrolysis effect. The results of CS were consistent with that of pKa values on both the yield of XOS and the inhibitor.ConclusionThe results based on pKa values and combined severity, a parameter associated with temperature and reaction time, concluded that acetic acid is a preferred catalyst. Combining the techno-economic analysis and environmental benefits, acetic acid hydrolysis process has lower factory production costs, and it is also an important metabolite and a carbon source for wastewater anaerobic biological treatment. In conclusion, production of xylo-oligosaccharides by acetic acid is an inexpensive, environment-friendly, and sustainable processing technique.

Highlights

Methods to produce XOS have been intensively investigated, including enzymatic hydrolysis, steam explosion, and acid hydrolysis
Cao et al Biotechnol Biofuels (2021) 14:69 economic and environmental benefits requires the application potential of agricultural and forestry wastes to be further explored. This was demonstrated in a number of studies that used lignocellulose found in rich amounts in agricultural and forestry waste, and is a valuable resource for industrial application
The kinetics of acidolysis by various acids and degradation of wheat straw Four low molecular weight organic acids at 0.8 mol/L concentration were analyzed in this study

Summary

Introduction

Methods to produce XOS have been intensively investigated, including enzymatic hydrolysis, steam explosion, and acid hydrolysis. Acid hydrolysis is currently the most widely used method to produce XOS due to its advantages of fewer processing steps, stronger raw material adaptability, higher yield, and better reproducibility. Organic acids such as acetic acid, formic acid and xylonic acid work better as compared with mineral acids. As a type of functional oligosaccharide, XOS has attracted much attention due to its unique physiological properties It was demonstrated in a number of studies that XOS can promote the proliferation of beneficial bacteria [7], strengthen immunity [8], prevent constipation, and lower serum cholesterol [9] among other benefits. In 2018, the European Union officially approved XOS as a new food additive

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