Effects of combined CaO-CO₂ detoxification treatment on the conversion of sugarcane bagasse enzymatic hydrolysate to xanthan gum

Abstract:

Replacing grain-derived carbon sources with non-grain biomass carbon sources for fermentation is a core research direction in the field of biomanufacturing. However, inhibitory byproducts present in the enzymatic hydrolysate of non-grain biomass severely restrict its practical application. We aim to reduce the dependence of xanthan gum fermentation on grain-based carbon sources, clarify the impacts of typical inhibitors from non-grain biomass enzymatic hydrolysate on xanthan gum synthesis, break through the existing application bottlenecks, and develop a green, low-loss and high-efficiency detoxification technology to overcome the inherent defects of traditional detoxification processes. In this study, we used sugarcane bagasse enzymatic hydrolysate as the fermentation carbon source, and the xanthan gum-producing strain Xanthomonas campestris 1.178 as the research object. We investigated the effects of furfural (FFR) and 5-hydroxymethylfurfural (HMF) on xanthan gum biosynthesis. To address the defects of high sugar loss and massive byproduct generation in the conventional CaO-H₃PO₄ detoxification process, we developed an innovative CaO-CO₂ combined detoxification process, and comparatively analyzed the physicochemical properties of xanthan gum produced via the two detoxification processes. We identified that acetic acid and isovaleric acid are the key inhibitory factors in sugarcane bagasse enzymatic hydrolysate that limit xanthan gum synthesis. After CaO-CO₂ treatment, we achieved retention rates of 98.23% for total sugar, 95.63% for reducing sugar, and 95.08% for glucose in the hydrolysate. We obtained a xanthan gum yield as high as 19.76 g/L, which was 19.75% higher than the yield from the CaO-H₃PO₄ treatment. The xanthan gum prepared in this study shared consistent infrared spectrum characteristics with commercially available xanthan gum, and we confirmed its excellent tolerance under low temperature, alkaline and high-salt conditions. The CaO-CO₂ detoxification process developed in this study realizes efficient conversion of sugarcane bagasse enzymatic hydrolysate to xanthan gum, and provides a brand-new green solution for the high-value utilization of non-grain biomass.