Journal of Environmental Research

PHOTOTROPHIC PHB PRODUCTION WITH CYANOBACTERIA BY USING LOW SOLIDS DIGESTATE

4^th Edition of International Conference on Environmental Science & Technology
March 29-31, 2018 Vienna, Austria

K. Meixner, C. Troschl, I. Fritz and B. Drosg

BIOENERGY 2020+ GmbH, Austria University of Natural Resources and Life Sciences, Austria

ScientificTracks Abstracts: J Environ Res

Abstract

With rising environmental pollution caused by persistent and petroleum-based plastics, the interest in biodegradable materials like poly-��-hydroxybutyrate (PHB) increases. Currently, PHB production is based on heterotrophic bacteria, using organic carbon sources from crops. To avoid the competition to food and feed production cyanobacteria, metabolizing CO2 e.g. from exhaust gas, can be used. For cultivating cyanobacteria at larger scales high amounts of mineral nutrients are needed. Due to this reason alternative nutrient sources, such as digestate, are required. In this study photoautotrophic PHB production with cyanobacteria was investigated, with emphasis on increasing the ecological and economic efficiency of the process by using anaerobic digestate as nutrient source as well by using the residual biomass. The results obtained herein demonstrate that low solids digestate, produced by anaerobic digestion thin stillage, is suitable to produce PHB with Synechocystis salina. By using digestate supernatant diluted 1/3, biomass and PHB concentrations of 1.6 g/L and 89 mg/L, respectively, were achieved within 40 days in a tubular photobioreactor system with a working volume of 200L. In mineral medium, optimised with regard to biomass and PHB production in a single cultivation stage, biomass and PHB concentrations of 2.1 g/L and 123 mg/L were obtained. The PHB quality was hardly influenced when digestate was used as nutrient source. Additionally, anaerobic digestion of residual biomass yielded in 348 Nm�³ CH4/t VS, being comparable with maize silage, a frequently used substrate in biogas plants. Other options would be to use the residual biomass as animal feed or fertiliser, since it still contained lipids (14 mg/g TS), proteins (242 mg/g TS) and carbohydrates (6 mg/g TS). Based on these results it can be concluded that photoautotrophic PHB production has a high potential to be connected to already existing processes, at which digestate and CO2 accrue. Keywords - Biorefinery, digestate, polyhydroxy butyric acid, Synechocystis slina Recent Publications 1. Meixner K, Kovalcik A, Sykacek E, Gruber-Brunhumer M, Zeilinger W, Markl K, Haas C, Fritz I, Mundigler N, Stelzer, F, Neureiter, M, Fuchs W, Drosg B (2018) Cyanobacteria Biorefinery - Production of poly(3-hydroxybutyrate) with Synechocystis salina and utilisation of residual biomass. J Biotechnol. 2018; 265:46-53 2. Kovalcik A, Meixner K, Mihalic M, Zeilinger W, Fritz I, Fuchs W, Kucharczyk P, Stelzer F, Drosg, B (2017) Characterization of polyhydroxyalkanoates produced by Synechocystis salina from digestate supernatant. Int J Biol Macromol. 2017; 102:497-504 3. Meixner, K; Fritz, I; Daffert, C; Markl, K; Fuchs, W; Drosg, B (2016) Processing recommendations for using lowsolids digestate as nutrient solution for poly-betahydroxybutyrate production with Synechocystis salina. J BIOTECHNOL. 2016; 240: 61-67. 4. Wagner J, Bransgrove R, Beacham TA, Allen MJ, Meixner K, Drosg B, Ting VP, Chuck CJ (2016) Co-production of biooil and propylene through the hydrothermal liquefaction of polyhydroxybutyrate producing cyanobacteria. BIORESOURCE TECHNOL. 2016; 207: 166-174 5. Meixner K, Fuchs W, Valkova T, Svardal K, Loderer C, Neureiter M, Bochmann G, Drosg B (2015) Effect of precipitating agents on centrifugation and ultrafiltration performance of thin stillage digestate. SEP PURIF TECHNOL. 2015; 145: 154-160.

Biography

K. Meixner is PhD student at the Institute of Environmental Biotechnology of University of Natural Resources, Vienna. Her research foci are algae/ cyanobacteria biotechnology, biorefinery, biogas production and digestate treatment. Currently, she is “Junior Researcher” at the Austrian Research Competence Centre “Bioenergy2020+” for the area “bioconversion and biogas systems”.

Email:katharina.meixner@bioenergy2020.eu