Pretreatment of lignocellulosic biomass using steam explosion or dilute acid results in production of prehydrolyzates (a liquid phase) mainly containing hemicellulose-derived sugars at low concentrations and inhibitory compounds. These inhibitory substances strongly affect enzymatic hydrolysis and reduce the productivity and yield of lignocellulosic ethanol fermentation. In addition, fermentation of low-concentration fermentable sugars in the prehydrolyzates leads to low ethanol concentration, which in turn leads to high operation cost of ethanol distillation. Therefore, in order to improve the effectiveness of prehydrolyzates fermentation, the prehydrolyzates should be detoxified to remove inhibitors and concentrated to increase sugar concentration prior to being used for ethanol fermentation.

Prof. WAN Yinhua and his colleagues at Institute of Process Engineering reported a one-step nanofiltration (NF) process for removal of inhibitors and concentration of fermentable sugars. The project was financially supported by the Chinese Academy of Sciences’ Knowledge Innovation Program (Grant No. KSCX1-YW-11D2).

They investigated concentration and purification of xylose and glucose in model solution containing furfural by using two commercial NF membranes (NF90 and NF270) and found that for both membranes, the retensions of the three solutes were significantly influenced by the operating conditions, such as feed pH and solutes concentration, permeation flux and temperature. NF90 was better than NF 270 in terms of sugars recovery. Concentration experiments with NF90 greatly increased the concentrations of xylose and glucose, while furfural concentration increased slightly. The authors proposed a NF process for simultaneous concentration and purification of lignocellulosic prehydrolyzates. It included concentrating prehydrolyzate with NF90 followed by diafiltration of the retentate to remove furfural. The experimental results show that NF could be a promising approach for concentration and purification lignocellulosic prehydrolyzates.

The research results were published in Bioresouce Technology (2011, 102: 7111-7118).

Corresponding author:

WAN Yinhua,

E-mail: yhwan@home.ipe.cn.