Positioning paper bij de inauguratie van Vincent Voet als lector Circular Plastics.
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Lignocellulose biorefining is a promising technologyfor the sustainable production of chemicals and biopolymers.Usually, when one component is focused on, the chemical natureand yield of the others are compromised. Thus, one of thebottlenecks in biomass biorefining is harnessing the maximumvalue from all of the lignocellulosic components. Here, we describea mild stepwise process in a flow-through setup leading to separateflow-out streams containing cinnamic acid derivatives, glucose,xylose, and lignin as the main components from differentherbaceous sources. The proposed process shows that minimaldegradation of the individual components and conservation oftheir natural structure are possible. Under optimized conditions,the following fractions are produced from wheat straw based ontheir respective contents in the feed by the ALkaline ACid ENzyme process: (i) 78% ferulic acid from a mild ALkali step, (ii) 51%monomeric xylose free of fermentation inhibitors by mild ACidic treatment, (iii) 82% glucose from ENzymatic degradation ofcellulose, and (iv) 55% native-like lignin. The benefits of using the flow-through setup are demonstrated. The retention of the ligninaryl ether structure was confirmed by HSQC NMR, and this allowed monomers to form from hydrogenolysis. More importantly, thecrude xylose-rich fraction was shown to be suitable for producing polyhydroxybutyrate bioplastics. The direct use of the xylose-richfraction by means of the thermophilic bacteria Schlegelella thermodepolymerans matched 91% of the PHA produced with commercialpure xylose, achieving 138.6 mgPHA/gxylose. Overall, the ALACEN fractionation method allows for a holistic valorization of theprincipal components of herbaceous biomasses.
Accumulation of non-degradable plastic waste in the environment might be prevented by the use of biodegradable polyhydroxyalkanoate (PHA). In this study, the thermophile Schlegelella thermodepolymerans produced up to 80 wt% PHA based on dry cell mass. The largest PHA granules were found in the cells within 48 h using 20 g/L xylose, a C/N ratio of 100, an initial pH of 7, at 50 °C. The substrate consumption, pH changes, and cell growth were monitored, revealing the time dependency of PHA production in S. thermodepolymerans. The metabolic pathways from xylose to PHA were identified based on proteomic analysis, revealing involvement of classic phaCAB, de novo fatty acid biosynthesis, and fatty acid β-oxidation. In addition, it was shown that S. thermodepolymerans degraded extracellular PHA with a high efficiency at 50 °C.
