Changes in the metabolism of the microalga Chlorella vulgaris when coimmobilized in alginate with the nitrogen-fixing Phyllobacterium myrsinacearum (original) (raw)
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Canadian Journal of Microbiology, 2002
Three strains of the freshwater microalgae used for wastewater treatment, Chlorella vulgaris and Chlorella sorokiniana co-immobilized separately in alginate beads with the microalgae-growth-promoting bacterium Azospirillum brasilense Cd, resulted in significant changes in microalgal-population size, cell size, cell cytology, pigment, lipid content, and the variety of fatty acids produced in comparison with microalgae immobilized in alginate without the bacterium. Cells of C. vulgaris UTEX 2714 did not change in size, but the population size within the beads significantly increased. On the other hand, C. vulgaris UTEX 395 cells grew 62% larger, but their numbers did not increase. The population of C. sorokiniana UTEX 1602 increased, but not their cell size. The content of pigments chlorophyll a and b, lutein, and violoaxanthin increased in all microalgal species. The lipid content also significantly increased in all three strains, and the number of different fatty acids in the microalgae increased from four to eight. This study indicates that the microalgae-growth-promoting bacterium induced significant changes in the metabolism of the microalgae.
Shining a Light on Wastewater Treatment with Microalgae
Arabian Journal for Science and Engineering
Microalgae can produce biofuels, nutriceuticals, pigments and many other products, but commercialization has been limited by the cost of growing, harvesting and processing algal biomass. Nutrients, chiefly nitrogen and phosphorus, are a key cost for growing microalgae, but these nutrients are present in abundance in municipal wastewater where they pose environmental problems if not removed. This is not a traditional review article; rather, it is a fact-based set of suggestions that will have to be investigated by scientists and engineers. It is suggested that if microalgae were grown as biofilms rather than as planktonic cells, and if internal illumination rather than external illumination were employed, then the use of microalgae may provide useful improvements to the wastewater treatment process. The use of microalgae to remove nutrients from wastewater has been demonstrated, but has not yet been widely implemented due to cost, and because microalgae derived from wastewater treatment has not yet been demonstrated as a commercial source for value-added products. Future facilities are likely to be called Municipal Resource Recovery Facilities as wastewater will increasingly be viewed as a resource for water, biofuels, fertilizer, monitoring public health and value-added products. Advances in photonics will accelerate this transition.
Applied Microbiology and Biotechnology, 2013
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Interactions between Microalgae and Bacteria in their Phycosphere
한국생물공학회 학술대회, 2014
Milk whey processing wastewaters (MWPWs) are characterized by high COD and organic nitrogen content; the concentrations of phosphorus are also relevant. A microalgal-based process was tested at lab scale in order to assess the feasibility of treating MWPW without any dilution or pre-treatment. Different microalgal strains and populations were tested. Based on the obtained results, Scenedesmus acuminatus (SA) and a mixed population (PM) chiefly made of Chlorella, Scenedesmus, and Chlamydomonas spp. were grown in duplicate for 70 days in Plexiglas column photobioreactors (PBRs), fed continuously (2.5 L culture volume, 7 days hydraulic retention time). Nutrient removal, microalgae growth, photosynthetic efficiency, and the composition of microalgal populations in the columns were monitored. At steady state, the microalgal growth was similar for SA and PM. The average removal efficiencies for the main pollutants were: 93% (SA), 94% (PM) for COD; 88% (SA) and 90% (PM) for total N; and 69% (SA) and 73% (PM) for total P. The residual pollution levels in the effluent from the PBRs were low enough to allow their discharge into surface waters; such good results were achieved thanks to the synergy between the microalgae and bacteria in the CO 2 and oxygen production/consumption and in the nitrogen mineralization.
Microalgae and wastewater treatment
Organic and inorganic substances which were released into the environment as a result of domestic, agricultural and industrial water activities lead to organic and inorganic pollution. The normal primary and secondary treatment processes of these wastewaters have been introduced in a growing number of places, in order to eliminate the easily settled materials and to oxidize the organic material present in wastewater. The final result is a clear, apparently clean effluent which is discharged into natural water bodies. This secondary effluent is, however, loaded with inorganic nitrogen and phosphorus and causes eutrophication and more long-term problems because of refractory organics and heavy metals that are discharged. Microalgae culture offers an interesting step for wastewater treatments, because they provide a tertiary biotreatment coupled with the production of potentially valuable biomass, which can be used for several purposes. Microalgae cultures offer an elegant solution to tertiary and quandary treatments due to the ability of microalgae to use inorganic nitrogen and phosphorus for their growth. And also, for their capacity to remove heavy metals, as well as some toxic organic compounds, therefore, it does not lead to secondary pollution. In the current review we will highlight on the role of micro-algae in the treatment of wastewater.
The roles of algae in improving aquaculture water quality are well-established. However, the integration of algae in a recirculating aquaculture systems (RAS) is less popular mainly due to the large area required for photosynthesis. As science progresses, a growing number of reports are available on the benefits of algae to water quality and fish health. This motivated the author to investigate the effects of algae on a RAS stability, by measuring the water quality and the effects on bacterial community composition in a RAS. A review was conducted on nitrogen removal by algae and the operation of an algae reactor in a RAS. This showed that a RAS configuration influence algae performance by affecting nitrogen loading and nitrogen species (ammonium versus nitrate), cultivation methods (suspended versus attached) and environmental conditions (light, temperature, pH, oxygen, and carbon dioxide). Next, a periphytic microalga, Stigeoclonium nanum was cultured in suspension or immobilized. The growth and nitrogen uptake of S. nanum was higher when immobilized than when cultured in suspension. S. nanum preferred ammonia rather than nitrate as nitrogen species. Further effects of S. nanum on the RAS water quality (total ammonia nitrogen (TAN), nitrite, nitrate, and phosphate) were also investigated. No difference of TAN between the RAS with algae (RAS+A) and the RAS without algae (RAS-A) was observed. However, nitrite, nitrate and phosphate were significantly lower in the RAS+A than in the RAS-A. When the RAS systems were perturbed by an acute pH drop (from pH 7 to 4 over three hours), no significant difference was observed between the RAS+A and the RAS-A on the resistance towards the stressor. This was shown by an increase in the TAN and the nitrite concentration in both treatments after the perturbation. However, the algae helped the RAS+A to regain a low nitrite level faster than the RAS-A. The diversity of bacterial community between the RAS+A and the RAS-A was not different, while the composition of bacterial community was significantly different between the RAS+A and the RAS-A, thus influencing the functioning of the RAS.
Environmental Technology, 2017
The aim of this study was to evaluate the effect of light intensity and temperature on nutrient removal and biomass productivity in a microalgae-bacteria culture and their effects on the microalgae-bacteria competition. Three experiments were carried out at constant temperature and various light intensities: 40, 85 and 125 µE•m-2 •s-1. Other two experiments were carried out at variable temperatures: 23 ± 2 and 28 ± 2 ºC at light intensity of 85 and 125 µE•m-2 •s-1 , respectively. The photobioreactor was fed by the effluent from an anaerobic membrane bioreactor. High nitrogen and phosphorus removal efficiencies (about 99%) were achieved under the following operating 2 conditions: 85-125 µE•m-2 •s-1 and 22 ± 1 ºC. In the microalgae-bacteria culture studied, increasing light intensity favoured microalgae growth and limited the nitrification process. However, a non-graduated temperature increase (up to 32ºC) under the light intensities studied caused the proliferation of nitrifying bacteria and the nitrite and nitrate accumulation. Hence, light intensity and temperature are key parameters in the control of the microalgae-bacteria competition. Biomass productivity significantly increased with light intensity, reaching 50.5 ± 9.6, 80.3 ± 6.5 and 94.3 ± 7.9 mgVSS•L-1 •d-1 for a light intensity of 40, 85 and 125 µE•m-2 •s-1 , respectively.
The Intertrophic Relationship between Algae and Bacteria from the Activated Microalgae Granules
Revista de Chimie, 2019
Activated microalgae granules, as a technology at its initial steps, require sustained efforts for a better understanding of the intertrophic relationship between algae and bacteria. The activated algae granules samples from extensive lab-scale sequencing batch reactor experiments were selected for a total DNA extraction and analysis. A relative quantitative analysis of bacterial genes involved in nitrification, denitrification, phosphorus accumulation as well as genes belonging to microalgae was performed by real-time PCR / qPCR. Microscopic investigations of activated microalgae granule showed a gradual decrease of microalgae concentration, together with an increase in bacterial populations inside the granule.