Sofie Thage Mortensen has conducted her Ph.D. thesis
in BioValue’s project 3.
Below is a short summary of her findings and information on the defense.


PhD title: Integration between enzyme technology and membrane separation in biorefinery processes

Lignocellulose is an abundant and renewable raw material with the potential to replace or supplement fossil resources as feedstock for production of various chemical products. However, in order to turn lignocellulosic biomass into valuable chemicals, several conversion and separation steps are required. The first step is biomass pretreatment, which typically results in a solid fraction rich in lignin and cellulose and a liquid fraction rich in hemicellulose, which may be partly or completely hydrolyzed to oligo- and monosaccharides (notably xylose).

The main objective of this thesis was the purification of xylose from glucose present in the biomass pretreatment liquors. The separation of xylose and glucose is challenging due to their similar structure, size and charge properties. In order to improve the separation potential, we proposed an enzymatic process for converting glucose to gluconic acid, a value-added biorefinery product widely used in the food and pharma industry, followed by separation of xylose from gluconic acid by nanofiltration.

In the first part of the PhD study, the efficiency of xylose purification by enzyme-assisted nanofiltration was evaluated based on a systematic parameter investigation on pure model solutions of xylose and gluconic acid. In the second part of the study, two different enzyme systems were investigated for the conversion of glucose to gluconic acid. The study showed that reactor configuration and substrate specificity had a crucial impact on the glucose conversion. As a final step, the enzyme system resulting in the highest xylose purification performance (when applied to pure model solutions of xylose and glucose) was investigated on genuine biomass liquors obtained from hydrothermal pretreatment of wheat straw, corn stover and Miscanthus stalks, respectively. When gel layer formation on the membrane surface was prevented, the biocatalytic productivity obtained for the three biomass liquors was the same as for the pure model solutions. However the downstream separation could potentially be enhanced, if new nanofiltration membranes, which are capable of maintaining their surface charge at high ionic strength, could be identified.

The knowledge gained during the PhD project could benefit industrial biorefinery processes, since biomass valorization could be maximized through integrated production of bioenergy and value-added co-products. Furthermore, the general principle of enzyme-assisted membrane separation could be applied to any process stream in which high purity of one component, present in a mixture of several compounds with similar chemical properties, is desired

We hope that you will participate at Sofie’s defense:

Time: Friday 7/7 2017 at 13 o’clock

Place: Room 003, building 229, DTU

Main supervisor: Associate professor Manuel Pinelo, Dept. of Chemical and Biochemical Engineering, Technical University of Denmark

Contact information: Sofie Thage Morthensen, e-mail: soth@kt.dtu.dk

Defense title: Integration between enzyme technology and membrane separation in biorefinery processes

Fotograf: Christian Ove Carlsson. Copyright: DTU Kemiteknik