13-33: Simultaneous aldose isomerization and separation/concentration of ketose by reactive extraction

Biomass hydrolysates often suffer from relatively low sugar concentration as well as contamination, those limiting the efficiency of subsequent bioconversion of sugar, especially fermentation due to sugar degradation and ligin derivatives. However, the current methods for sugar concentration and toxins removal are either engery intensive, not economically friendly, or unfavorable in industrial scale.

Liquid-liquid extraction of sugars from ionic liquid and/or aqueous solution into an organic phase containing lipophilic boronic acid has been used to recover both glucose and xylose. However, the pH requirement of aqueous phase, which is pH 11, was much higher than the ones for biomass hydrolysats by using diluted acid or ionic pretreatment method. And also, the molar ratio of boronic acid to sugars was relative high, requiring lots of boronic acid.

In this research, a modified reactive extraction approach to extract ketose sugars by using liquid-liquid extraction, which is more favorable for downstream utilization and also more favorable extracted by using boronic acid, was proposed.

We also present here results achieved for sugar separation and concentration with isomerization of the aldose sugars to their ketose forms. We have conducted the isomerization and reactive extraction of sugar at pH 8.5, a pH lower than that used for aldose sugar extraction. We have optimized the ratio of boronic acid to aldose sugar under these isomerization and extraction conditions and compare our results to reactive extraction of aldose sugars at pH 11.