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Publication type: Master thesis
Title: Cultivation of PHB-producing cyanobacteria in wastewater on laboratory and pilot-scale
Authors: Mariotto, Marina
Advisors / Reviewers: Refardt, Dominik
Fritz, Ines
Egloff, Sophia
DOI: 10.21256/zhaw-25201
Extent: 29
Issue Date: 2022
Publisher / Ed. Institution: ZHAW Zürcher Hochschule für Angewandte Wissenschaften
Publisher / Ed. Institution: Winterthur
Language: English
Subjects: Wastewater treatment; Liquid digestate; Aquaculture water; Bioplastic; Biopolymer; Nitrogen mass balance
Subject (DDC): 579: Microbiology
Abstract: The cultivation of PHB-producing cyanobacteria is a promising process to optain the raw material for bio-based and biodegradable plastics. To commercialise photoautotrophic PHB production, the cultivation needs to be scaled up in open cultivation systems. Further, the use of wastewater as nutrient source improves the resource efficiency of the process, making it cheaper and more sustainable. Here, the feasibility of these steps was tested. First, the suitability of different PHB-producing cyanobacteria was compared in laboratory scale cultivations. Then, the species Synechococcus leopoliensis was cultivated in an open thin-layer photobioreactor (18 m2, 200 L), using a mineral medium, water from recirculating aquaculture systems and pre-processed liquid digestate as nutrient sources. Cultivations in all three media were successful. Cultivation in mineral medium resulted in both the highest final biomass yield (6 g L-1) and productivity (0.7 g L-1 d-1). Both wastewater-based media showed lower biomass yields and productivities (2 g L-1 and 0.25–0.3 g L-1 d-1). However, due to differences in the cultivation conditions (e.g. temperature, nutrient supply), final biomass yield and productivity do not represent the performance of the cultivations adequately. Therefore, relative parameters such as nitrogen and energy conversion ratios were applied. All cultivations in the open system were continued in the laboratory, where cultures were starved for 10 days under nutrient-depleted conditions (without nitrogen, phosphorus and both). This yielded comparatively low amounts of PHB (< 1 %dw). The comparison of the results suggest that PHB yields were influenced more by the initial cultivation condition than by the specific type of nutrient depletion. Thus, while the cultivation with waste streams in an open system is feasible, environmental parameters seem to influence PHB yields considerably and must be taken into account for the optimisation of the complete process.
License (according to publishing contract): CC BY 4.0: Attribution 4.0 International
Departement: Life Sciences and Facility Management
Appears in collections:Masterarbeiten Umwelt und natürliche Ressourcen

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