In the scope of BRISK2 European project, I had the opportunity to visit LNEG for two weeks between the end of October/early November 2018. The purpose of the visit was the production of purified hemicellulosic oligosaccharides from various biomasses. The Bioenergy team of LNEG has a long experience in fractionation processes of lignocellulosic biomass and is one the rare laboratories to process such fractionation in concentrated medium and at a kilo-lab scale. LNEG is also developing an expertise in characterization and purification techniques of biomass fractions.
During my stay, I performed several experiments of autohydrolysis of different types of biomasses (herbaceous, and woody materials) in a 2 L autoclave reactor (Picture 1). The reaction consists in heating biomass with liquid water under controlled heating conditions so that the water attacks the lignocellulose structure and partially dissolves it. In fact, during the reaction, the hemicellulose is solubilized and eventually hydrolysed into the liquid phase. After the reaction, the solid and liquid phases are separated using a hydraulic press to maximize the liquid recovery. The liquid phase is characterized by HPLC methods with and without post-hydrolysis treatment in order to fully quantify both the oligomeric and monomeric sugars. Then it was centrifuged, filtrated and concentrated by evaporation of water under reduced pressure. The solid biomass was dried and stored for future applications regarding biofuels production.
The purification of lignocellulose fractions is still a challenge at the moment. In this project, two purification techniques were tested on the liquid phase produced by autohydrolysis: membrane filtration and chromatographic separation. Membrane filtration was performed in a dedicated membrane filtration unit (Picture 2) and allowed to concentrate the hydrolysate and remove organic acids. Chromatographic separation was performed at a large scale (Pictures 3 & 4) using 50 mL of concentrated hydrolysate. It led to the separation of oligosaccharides and sugars and small molecules. All the fractions obtained were analysed by HPLC and spectrophotometry.
At the end of the visit, I had about ten hydrolysates and numerous samples to take back to LGPC where they will be analysed by complementary techniques and used as starting material for a new project on hemicellulose catalytic transformation.
Thanks to BRISK2, I had the chance to use LNEG facilities that are not available in LGPC and that will boost my research projects. The BRISK2 stay was also the opportunity to create a connection between LNEG and LGPC. A collaboration project was already submitted to the Pessoa program and fruitful exchanges are expected in a near future.