Márcia D. Zambon

Low liquid–solid ratio (LSR) hot water pretreatment of sugarcane bagasse

Low liquid–solid ratio (LSR) can be used to obtain high-content xylo-oligosaccharide (XOS) spend liquor by hot water pretreatment. Developing a technology based on low LSR results in more efficient water usage in the system and thus in lower capital and operating costs. Xylans from xylan rich agro-industrial waste are abundant hemicellulosic polymers with enormous potential for industrial applications. Currently, freeze-dried xylo-oligosaccharides are used as bio-based polymers and hydrolysates containing high xylose contents are converted to several chemical products. In this study, sugarcane bagasse was treated with water at low LSRs and mild temperatures in order to assess the effects of varying the pretreatment conditions on the xylo-oligosaccharide and xylose concentrations, and use a central composite experimental design to optimize the process parameters. The pretreatments were performed in the ranges temperature: 143.3–176.7 °C, time: 20–70 min and LSR: 1 : 1 to 11 : 1 (g g−1). The maximum concentrations of xylose and xylan were 13.76 and 36.18 g L−1 (equivalent to 48.29 g L−1 of xylan), respectively, which were achieved by treating bagasse at 170 °C for 60 min, with LSR of 3 g g−1. The amount of xylan removed under these conditions was almost 57%. The soluble xylan consisted mainly of xylo-oligosaccharides (74 wt% of the identified compound in the spent liquor).

Effect of acid concentration and pulp properties on hydrolysis reactions of mercerized sisal.

The influence of sulfuric acid concentration (H2SO4 5-25%, 100°C), crystallinity and fibers size on the hydrolysis reaction of sisal pulps were investigated, with the goal of evaluating both the liquor composition, as an important step in the production of bioethanol, and the residual non-hydrolyzed pulp, to determine its potential application as materials. Aliquots were withdrawn from the reaction media, and the liquor composition was analyzed by HPLC. The residual non-hydrolyzed pulps were characterized by SEM, their average molar mass and crystallinity index, and their size distribution was determined using a fiber analyzer. Sulfuric acid 25% led to the highest glucose content (approximately 10gL(-1)), and this acid concentration was chosen to evaluate the influence of both the fiber size and crystallinity of the starting pulp on hydrolysis. The results showed that fibers with higher length and lower crystallinity favored glucose production in approximately 12%, with respect to the highly crystalline shorter fibers.