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

• Published in: Chemical and Biochemical Engineering Quarterly Vol. 29; no. 2; pp. 99 - 112
• Main Author: Haas, C.
• Format: Journal Article Paper
• Language: English
• Published: Croatian Association of Chemical Engineers 2015; Hrvatsko društvo kemijskih inženjera i tehnologa
• Subjects: batch fermentation; by-product; Cichorium intybus; Cupriavidus necator; food residue; fructose; hydrolysate; inulin; P3HB; Physiological aspects; Polyhydroxybutyrate; polymer characterisation; pre-treatment; Proteobacteria; Spain
• ISSN: 0352-9568; 1846-5153
• DOI: 10.15255/CABEQ.2014.2250

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(®-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.sup.-1] sugars and 0.7 g [L.sup.-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.sup.-1] with a PHB content of 66 % in dry mass within 5 days. C. necator DSM 531 yielded 3.5 g [L.sup.-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.sup.-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. Key words: Cichorium intybus, fructose, inulin, by-product, food residue, pre-treatment, hydrolysate, batch fermentation, Cupriavidus necator, P3HB, polymer characterisation