Search Results (3)

Here, a syntrophic process was developed to produce polyhydroxy-β-butyrate (PHB) from a gas stream containing CH₄ and CO₂ without an external oxygen supply using a combination of methanotrophs with the community of oxygenic photogranules (OPGs). The co-culture features of Methylomonas sp. DH-1 and Methylosinus trichosporium OB3b were evaluated under carbon-rich and carbon-lean conditions. The critical role of O₂ in the syntrophy was confirmed through the sequencing of 16S rRNA gene fragments. Based on their carbon consumption rates and the adaptation to a poor environment, M. trichosporium OB3b with OPGs was selected for methane conversion and PHB production. Nitrogen limitation stimulated PHB accumulation in the methanotroph but hindered the growth of the syntrophic consortium. At 2.9 mM of the nitrogen source, 1.13 g/L of biomass and 83.0 mg/L of PHB could be obtained from simulated biogas. These results demonstrate that syntrophy has the potential to convert greenhouse gases into valuable products efficiently. Full article

Wastewater generation is a worldwide problem, and its treatment is an important practice for maintaining public health and environmental protection. Oxygenic photogranules (OPGs) are a relatively novel type of biogranules that have the potential to substitute the conventional activated sludge (AS) process due to the production of in situ oxygen, better physical properties such as settling velocity and density, as well as carbon and nutrient removal efficiencies. The formation of the granules is attributed to many factors, among which the most influential are light intensity, ammonium nitrogen concentration, and the presence of filamentous cyanobacteria that, along with heterotrophic microorganisms situated in the granule’s core, create a self-sustainable system that combines denitrification, carbon removal, and oxygen production. Hydrostatic and hydrodynamic cultivations are two ways that allow for obtaining OPGs. These two cultivation methods lead to the formation of various types of granules which differ in both structures as well as physical properties. This review article aims to aggregate the available literature information regarding the methods of cultivation of OPGs, their formation mechanisms, and factors that influence the cultivation as well as an overview of studies that were conducted thus far concerning this type of biogranules. Additionally, further research directions are proposed in the article. Full article

The microalgae–bacteria consortium is a promising and sustainable alternative for industrial wastewater treatment, since it may allow good removal of organic matter and nutrients, as well as the possibility of producing products with added value from the algae biomass. This research investigated the best bacterial and microalgae inoculation ratio for system start-up and evaluation of removing organic matter (as chemical oxygen demand (COD)), ammoniacal nitrogen (NH₄⁺–N), nitrite nitrogen (NO₂⁻–N), nitrate nitrogen (NO₃⁻–N), phosphate phosphorus (PO₄³⁻–P) and biomass formation parameters in six photobioreactors with a total volume of 1000 mL. Reactors were operated for 14 days with the following ratios of pulp mill biomass aerobic (BA) and Scenedesmus sp. microalgae (MA): 0:1 (PBR1), 1:0 (PBR2), 1:1 (PBR3), 3:1 (PBR4), 5:1 (PBR5), and 1:3 (PBR6). Results show that COD removal was observed in just two days of operation in PBR4, PBR5, and PBR6, whereas for the other reactors (with a lower rate of initial inoculation) it took five days. The PBR5 and PBR6 performed better in terms of NH₄⁺–N removal, with 86.81% and 77.11%, respectively, which can be attributed to assimilation by microalgae and nitrification by bacteria. PBR6, with the highest concentration of microalgae, had the higher PO₄³⁻–P removal (86%), showing the advantage of algae in consortium with bacteria for phosphorus uptake. PBR4 and PBR5, with the highest BA, led to a better biomass production and sedimentability on the second day of operation, with flocculation efficiencies values over 90%. Regarding the formation of extracellular polymeric substances (EPS), protein production was substantially higher in PBR4 and PBR5, with more BA, with average concentrations of 49.90 mg/L and 49.05 mg/L, respectively. The presence of cyanobacteria and Chlorophyceae was identified in all reactors except PBR1 (only MA), which may indicate a good formation and structuring of the microalgae–bacteria consortium. Scanning electron microscopy (SEM) analysis revealed that filamentous microalgae were employed as a foundation for the fixation of bacteria and other algae colonies. Full article