Cornelia Haas studied molecular biology and biological chemistry at the University of Vienna, Columbia University in the City of New York and the Dublin Institute of Technology. Currently she is doing her PhD project on the production of PHB from alternative feedstocks at the University of Natural Resources and Life Sciences Vienna. She has (co-)authored several papers and presented her work at the Renewable Resources and Biorefinery Conference in Spain (2014).
We developed a cell-recycle membrane bioreactor for the high-cell-density production of poly(3-hydroxybutyrate) (PHB). This fermentation strategy is feasible for low carbon concentrations in the feed stream, as often found in agricultural residues. Cupriavidus necator DSM 545 was continuously supplied with medium containing 50 g/L of glucose. A constant working volume inside the bioreactor was maintained by an external polysulfone microfiltration membrane module. The PHB-production phase was started after 8 hours by supplying nitrogen-free medium. After another 32 hours, 52 g/L dry biomass were accumulated containing 92% PHB, resulting in a high productivity of 1.2 g PHB/Lh.
Cellulose is the most abundant macromolecular on earth observed in large quantity from nature which is predominantly generated by vascular plant and algae, but also by bacteria. Bacterial cellulose (BCel) exhibits the unique physical properties at nanoscale network (i.e. high water content and high tensile strength), and does not require extra processing steps to remove impurities such as lignin, pectin, and hemicellulose. Previous study demonstrated that BCel can be produced semi-continuously utilizing PCS rotating disk bioreactor (PCS-RDB). In this study, different additives including avicel, carboxymeylcellulose, agar and sodium alginate were added into culture medium in PCS-RDB to improve the productivity of BCel and its material property. The produced BCel was analyzed using fourier transform infrared spectroscopy (FTIR), scan electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and dynamic mechanical analysis (DMA). The results demonstrated that both CMC and avicel addition can increase the productivity of BCel in PCS-RDB. The highest BCel production reached 0.64 g/slice when 0.8% of avicel was added. The FTIR and XRD results indicated that CMC and avicel might be incorporated into BCel during production, and disordered BCel structure to decrease its crystallinity. The SEM result showed that the incorporated additives may attach on BCel fibers and increase fiber size. In future work, dynamic mechanical analysis (DMA) should be finish to confirm the effects of different additives addition in mechanical property.