Simultaneous posthydrolysis and liquid–liquid extraction: a SIMPLLE process to detoxify eucalyptus prehydrolysis liquor

• Published in: Biomass conversion and biorefinery Vol. 14; no. 22; pp. 29159 - 29173
• Main Authors: Almhofer, Lukas, Paulik, Christian, Bischof, Robert H.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2024; Springer Nature B.V
• Subjects: Aliphatic alcohols; Biotechnology; Carbohydrates; Design of experiments; Energy; Eucalyptus; Fermentation; High temperature; Inhibitors; Kraft process (woodpulp); Lignin; Liquid-liquid extraction; Liquor; Original Article; Raw materials; Renewable and Green Energy; Size exclusion chromatography; Solvents; Sugar; Size-exclusion chromatography; Solvent screening; Sugar recovery; Lignin solubility; Response surface methodology; Detoxification
• ISSN: 2190-6815; 2190-6823
• DOI: 10.1007/s13399-023-04570-6

The prehydrolysis liquor from the prehydrolysis Kraft process is rich in sugars and could thus serve as a sustainable feedstock for the production of various chemicals. However, its industrial utilization is impeded by the presence of fermentation inhibitors and extensive lignin precipitation, the latter receiving only little attention in the literature. In order to provide a feedstock suitable for biotechnological or chemical conversion, the prehydrolysis liquor from eucalyptus wood must be detoxified whilst preventing the precipitation of lignin. To increase the yield of monomeric sugars, acid posthydrolysis should be investigated. Various solvents and solvent mixtures were screened for the high temperature liquid–liquid extraction of isothermally separated prehydrolysis liquor. Their capability to prevent lignin precipitation and to extract fermentation inhibitors was assessed using mass balances and size-exclusion chromatography. Based on the solvent screening, a process for simultaneous posthydrolysis and liquid–liquid extraction of eucalyptus prehydrolysis liquor was proposed and investigated using statistic experimental design. Liquid–liquid extraction using aliphatic alcohols effectively prevents lignin precipitation, and the addition of 25% (w/w) tri- n -octylamine was found to increase the overall inhibitor extraction efficiency. The conditions for the simultaneous posthydrolysis were investigated using a Box-Behnken experimental design, allowing for a maximum monomeric sugar yield of 83.0% at a sugar purity of 91.6%. The simultaneous posthydrolysis and liquid-liquid extraction (SIMPLLE) process thus avoids industrial-level problems associated with lignin precipitation. It provides a carbohydrate-rich stream with low levels of fermentation inhibitors, enabling further conversion to value added products.