Optimization and modeling of diananofiltration process for the detoxification of ligno-cellulosic hydrolysates - Study at pre-industrial scale

•Lignocellulosic hydrolysate detoxification is optimized by NF at spiral-wound scale.•Synthetic solution contains three sugars and five inhibitors.•Sugar sorption on NF membranes is highlighted and quantified.•Fermentation tests with P. stipitis are run on processed hydrolysates.•Diananofiltration with DK followed by concentration produces a fermentable solution.

In order to improve bioethanol production by yeast fermentation of lignocellulosic hydrolysates, sugar/inhibitor separation by nanofiltration was studied on a bench-scale unit equipped with a spiral-wound membrane. Therefore, a model solution containing 3 sugars and 4 inhibitors was treated with two previously selected membranes (NF270 from DOW Filmtec and DK from GE Osmonics). Both membranes led to high sugar rejection, especially at high permeate flux (>90% for glucose and arabinose and >85% for xylose). Although its water permeability was smaller, DK membrane was preferred for its higher transmission of the inhibitors, especially for the largest ones (vanillin and 5-hydroxymethyl furfural), ensuring a better detoxification level. Diafiltration was applied to improve sugar purity of the treated hydrolysate. With a diavolume equivalent to 1.25 times that of the feed, acetic acid concentration was divided by 5 and brought back to concentrations lower than 1 g L−1. A simulation model was proposed to predict the diavolume to apply, depending on the initial concentrations. Finally, processed hydrolysates were tested for the fermentation ability with a Pichia stipitis species. Fermentation tests showed that diafiltration followed by concentration led to retentates as fermentable as an equivalent pure sugars solution.