Intensification of wheat straw autohydrolysis at minimal water input: Advancing a novel hemicellulose-first approach

Abstract

The autohydrolysis of wheat straw, as a key step in a hemicellulose-first concept, was investigated with a focus on separating xylose-based oligomers and water-soluble polymers. The feedstock preparation and the autohydrolysis with saturated steam (avoiding explosion and additional auxiliaries) are aligned to produce a hemicellulose hydrolysate rich in non-monomeric xylose at low liquid-to-solid ratios and mild reaction temperatures. Using a tailored experimental design and regression models, the influence and interactions of reaction temperature, reaction time, and dry mass content were systematically studied. For the first time, highly significant models for biomass solubility, yield of non-monomeric xylose, share of non-monomeric xylose and inorganics content of the hydrolysate were derived in conjunction. The findings highlight the crucial influence of dry mass content, particularly under conditions of low water input, with an optimal performance identified below 50 %. High arabinoxylan solubilization (77 %) and xylose recovery as non-monomers (85 %) were achieved at a liquid-to-solid ratio of 1.5, without the need for extensive biomass size reduction. At a wheat straw dry mass content of 40 % and a severity factor of 3.7 (170 °C, 40 min), the resulting hydrolysate dry mass contained 67 % arabinoxylan, 8.6 % glucan and only 6.8 % phenolic and 2.5 % inorganic compounds. The results offer valuable insights into systematic autohydrolysis interactions and provide a framework for minimizing water and energy demands - key challenges in terms of green chemistry and industrial applications.