Production of PHB from Chicory Roots – Comparison of Three Cupriavidus necator Strains

C. Haas, V. Steinwandter, E. Diaz De Apodaca, B. Maestro Madurga, M. Smerilli, T. T. Dietrich and M. Neureiter

Abstract
Chicory roots from hydroponic salad cultivation are an abundant food residue in Navarra (Spain) that are underutilized to date. Aiming at a holistic utilization of resources, we report here the first process using chicory root hydrolysate for the production of poly([R]-3-hydroxybutyrate) (PHB). The polymer can be used for packaging material made for the locally produced vegetables. In the first step, we developed a pre-treatment process to obtain a hydrolysate, which contained 34 g L–1 sugars and 0.7 g L–1 total Kjeldahl nitrogen. This hydrolysate was used as fermentation substrate for three PHB-producing strains. Cupriavidus necator DSM 428 reached a dry biomass concentration of 11.3 g L–1 with a PHB content of 66 % in dry mass within 5 days. C. necator DSM 531 yielded 3.5 g L–1 dry biomass containing 46 % PHB within the same period. C. necator DSM 545 was superior over the other two in that 14.0 g L–1 of biomass containing 78 % PHB after only 3 days were obtained. These results show that even within the same species, the productivities on natural substrates are very different. The produced polymers were extracted using chloroform, and several thermo-physical parameters are in good accordance with published data. Overall, our holistic approach and the encouraging results prove that chicory roots are a viable fermentation substrate for PHB-production.

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Keywords
Cichorium intybus, fructose, inulin, by-product, food residue, pre-treatment, hydrolysate, batch fermentation, Cupriavidus necator, P3HB, polymer characterisation