Xylooligosaccharides production chain in sugarcane biorefineries: From the selection of pretreatment conditions to the evaluation of nutritional properties

Abstract

Xylooligosaccharides (XOs) are xylose oligomers that stimulate the growth of probiotic microorganisms and the production of substances with antimicrobial activity, such as bacteriocins. XOs are of great interest to the food and pharmaceutical industries and represent a promising product for the valorization of sugarcane bagasse in a biorefinery context. Here, the whole XOs production chain from sugarcane bagasse was studied, starting with biomass pretreatment, enzymatic hydrolysis of the hemicellulose fraction, purification and evaluation of nutritional properties of the final product. Hydrothermal and organosolv pretreatments stood out among four pretreatment alternatives, solubilizing hemicellulose mainly in the form of oligomers. Hydrothermal conditions for the highest XOs yield were determined (185 °C, 10 min, 1:10 solid:liquid ratio). Enzymatic conversion to XOs using an endoxylanase reached app. 90 %, for both hydrothermal and organosolv liquors. Prebiotic and antimicrobial properties of the XOs obtained after hydrothermal and organosolv pretreatments were evaluated. Both XOs presented probiotic activity, but substantially superior results were achieved for the hydrothermal pretreatment. XOs liquors were further purified using adsorption on activated charcoal and the purified XOs liquor significantly increased the cell concentration of probiotic lactic bacteria (L. acidophilus, L. reuteri and L. rhamnosus). The presence of bacteriocins with antimicrobial activity against Bacillus subtilis was also detected in culture plates (40 AU/mL). Although still requiring further optimization of purification steps, the results provide important information for developing sugarcane biorefineries producing XOs.