Sugar monomer and oligomer solubility: data and predictions for application to biomass hydrolysis

Oligomer solubility could potentially play an important role in controlling the rates and yields in the thermochemical hydrolysis of hemicellulose as a pretreatment for subsequent enzymatic conversion of cellulose. However, limited data or models are available to describe the aqueous solubility of sugar monomers and oligomers. In this work, we measured the solubilities of sugars common to many biomass feedstocks in the temperature range of 25-30 degrees C. Then we reviewed solubility models for sugars from the open literature. Finally, we applied models to test their ability to describe this and other data reported in the literature. It was found that the solubility of sugar monomers was not well described by the ideal solubility law or other more complex models. However, with an empirical adjustment to the enthalpy of fusion, the ideal solubility law was able to approximately predict the solubility of cello-oligomers. Based on these results, solubilities for low molecular weight xylo-oligomers are predicted to investigate their possible importance in pretreatment and define further experimental measurements needed to improve our understanding of sugar and oligomer solubility.