Preliminary results and status of Project 3, March 2017
In Project 3 we work to understand biomass fractionation and upgrading through development of innovative methods leading to improved process economy.
We map the chemical and physical biomass properties in response to pretreatment severity in order to determine the compact cell wall recalcitrance that underpins slow/incomplete cellulose digestibility in biomass. One of these physical biomass properties are e.g. biomass-water interactions which has shown to be correlated to cellulase digestibility of the biomass. Understanding which underlying mechanisms governs this and whether chemical or alternative enzymatic treatments are able to affect the biomass/water interaction e.g. in lignin dewatering steps are of interest for improving biorefining processes and process economy. Across the project, we work with a range of pretreated biomasses based on wheat straw, corn stover and miscanthus stalks which have been thoroughly analyzed for sugar and lignin composition incl. the use of comprehensive microarray polymer profiling.
In project 3 we optimize and develop novel methods to upgrade the value of the sugars from enzymatic saccharification of biomass. Using enzyme-assisted nanofiltration, we are able to convert glucose to value-added product gluconic acid by the enzymes glucose oxidase and catalase while using a negatively charged nanofiltration membrane to further purify xylose from the gluconic acid (Fig. 1). In another setup, we have from a glucose and xylose mix produced gluconic acid and lactic acid via enzymatic cofactor-dependent catalysis of glucose to gluconic acid and pyruvate to lactic acid, respectively, while separating xylose, gluconic acid and lactic acid in downstream nanofiltration steps. To produce cleaner sugar streams, we furthermore investigate the purification of biomass hydrolysate streams by removal of salts and degradation products in membrane filtration steps and study fouling effects.
Figure 1: Enzyme-assisted nanofiltration using the enzymes glucose oxidase (GOD) and catalase (CAT) to firstly produce gluconic acid from glucose and secondly by separating gluconic acid from xylose exploiting the different charges of the products.