Poly-β-hydroxybutyrate (PHB) is a potential source of biodegradable plastics that are environmentally friendly due to their complete degradation to water and carbon dioxide. This study aimed to investigate PHB production in the cyanobacterium Synechocystis sp. PCC6714 MT_a24 in an outdoor bioreactor using urban wastewater as a sole nutrient source. The culture was grown in a thin-layer raceway pond with a working volume of 100 L, reaching a biomass density of up to 3.5 g L-1 of cell dry weight (CDW). The maximum PHB content was found under nutrient-limiting conditions in the late stationary phase, reaching 23.7 ± 2.2% PHB per CDW. These data are one of the highest reported for photosynthetic production of PHB by cyanobacteria, moreover using urban wastewater in pilot-scale cultivation which multiplies the potential of sustainable cultivation approaches. Contamination by grazers (Poterioochromonas malhamensis) was managed by culturing Synechocystis in a highly alkaline environment (pH about 10.5) which did not significantly affect the culture growth. Furthermore, the strain MT_a24 showed significant wastewater nutrient remediation removing about 72% of nitrogen and 67% of phosphorus. These trials demonstrate that the photosynthetic production of PHB by Synechocystis sp. PCC6714 MT_a24 in the outdoor thin-layer bioreactor using urban wastewater and ambient carbon dioxide. It shows a promising approach for the cost-effective and sustainable production of biodegradable carbon-negative plastics. KEY POINTS: • High PHB production by cyanobacteria in outdoor raceway pond • Urban wastewater used as a sole source of nutrients for phototrophic growth • Potential for cost-effective and sustainable production of biodegradable plastics.

• Klíčová slova
• Biodegradable plastics, Polyhydroxybutyrate, Raceway pond cultivation, Synechocystis, Urban wastewater,
• MeSH
• biologicky odbouratelné plasty * MeSH
• hydroxybutyráty MeSH
• odpadní voda MeSH
• oxid uhličitý MeSH
• polyestery MeSH
• rybníky MeSH
• Synechocystis * MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• biologicky odbouratelné plasty * MeSH
• hydroxybutyráty MeSH
• odpadní voda MeSH
• oxid uhličitý MeSH
• poly-beta-hydroxybutyrate MeSH Prohlížeč
• polyestery MeSH

The microalga Scenedesmus sp. (Chlorophyceae) was cultured in a raceway pond (RWP) placed in a greenhouse. The objective of this case study was to monitor the photosynthesis performance and selected physicochemical variables (irradiance, temperature, dissolved oxygen concentration) of microalgae cultures in situ at various depths of RWP. The data of actual photochemical yield Y(II), the electron transport rate monitored by in vivo chlorophyll fluorescence and photosynthetic oxygen production both in situ and ex situ revealed that (i) even in diluted cultures (0.6 g DW L-1), the active photic layer in the culture was only about 1 cm, indicating that most of the culture was "photosynthetically" inactive; (ii) the mechanism of non-photochemical quenching may not be fast enough to respond once the cells move from the surface to the deeper layers; and (iii) even when cells were exposed to a high dissolved oxygen concentration of about 200% sat and higher, the cultures retained a relatively high Y(II) > 0.35 when monitored in situ. The presented work can be used as exemplary data to optimize the growth regime of microalgae cultures in large-scale RWPs by understanding the interplay between photosynthetic activity, culture depth and cell concentration.

• Klíčová slova
• RWP, Scenedesmus, chlorophyll (Chl) fluorescence, electron transport, green microalgae, non-photochemical dissipation, oxygen production, photic layer, photosynthesis,
• Publikační typ
• časopisecké články MeSH

The present work characterizes a submerged aerated hollow fiber polyvinylidene fluorid (PVDF) membrane (0.03 μm) device (Harvester) designed for the ultrafiltration (UF) of microalgae suspensions. Commercial baker's yeast served as model suspension to investigate the influence of the aeration rate of the hollow fibers on the critical flux (CF, J c) for different cell concentrations. An optimal aeration rate of 1.25 vvm was determined. Moreover, the CF was evaluated using two different Chlorella cultures (axenic and non-axenic) of various biomass densities (0.8-17.5 g DW/L). Comparably high CFs of 15.57 and 10.08 L/m/2/h were measured for microalgae concentrations of 4.8 and 10.0 g DW/L, respectively, applying very strict CF criteria. Furthermore, the J c-values correlated (negative) linearly with the biomass concentration (0.8-10.0 g DW/L). Concentration factors between 2.8 and 12.4 and volumetric reduction factors varying from 3.5 to 11.5 could be achieved in short-term filtration, whereat a stable filtration handling biomass concentrations up to 40.0 g DW/L was feasible. Measures for fouling control (aeration of membrane fibers, periodic backflushing) have thus been proven to be successful. Estimations on energy consumption revealed very low energy demand of 17.97 kJ/m3 treated microalgae feed suspension (4.99 × 10-3 kWh/m3) and 37.83 kJ/kg treated biomass (1.05 × 10-2 kWh/kg), respectively, for an up-concentration from 2 to 40 g DW/L of a microalgae suspension.

• Klíčová slova
• energy, filtration, harvesting, membrane, microalgae,
• Publikační typ
• časopisecké články MeSH

The following series of articles form a special issue organized by the Algatech Center of the Institute of Microbiology CAS dedicated to the memory of Dr. Ivan Šetlík.

• MeSH
• biopaliva dějiny   MeSH
• dějiny 20. století MeSH
• dějiny 21. století MeSH
• fotosyntéza MeSH
• mikrobiologie dějiny   MeSH
• sinice genetika   metabolismus   účinky záření   MeSH
• Check Tag
• dějiny 20. století MeSH
• dějiny 21. století MeSH
• Publikační typ
• biografie MeSH
• historické články MeSH
• oslavné články MeSH
• Geografické názvy
• Československo MeSH
• Názvy látek
• biopaliva MeSH

• O autorovi
• Šetlík, Ivan