Microalgae Bacteria Research Articles

Assessment of the oxygen dynamics in microalgae–bacteria systems through respirometry

AbstractBACKGROUNDA microalgae–bacteria consortium applied to the treatment of domestic wastewater can be an alternative to reduce the energy consumption of aerobic systems if the algal biomass produces enough oxygen for bacterial consumption. This study proposed to evaluate the microalgal production of photosynthetic O2 and consumption by heterotrophic organic matter‐removing and autotrophic nitrifying bacteria through respirometric tests.RESULTSAggregates composed of predominantly spherical green microalgae and bacteria were formed in a photosequencing batch reactor, with 6 h cycles, and fed with synthetic domestic wastewater. Biomass reached 800 mgVSS L−1 and chlorophyll‐a content of 4 mg gVSS−1. Photosynthetic oxygen production reached 33.4 mgO2 gSS−1 h−1. Through respirometric tests and oxygen mass balance, oxygen consumption rates by ordinary heterotrophic bacteria (5.9 mgO2 gSS−1 h−1), ammonia‐oxidizing bacteria (8.67 mgO2 gSS−1 h−1) and nitrite‐oxidizing bacteria (0.78 mgO2 gSS−1 h−1) were obtained.CONCLUSIONPhotosynthetic oxygen production was 28% higher than the total O2 required by bacteria. Under the conditions studied, an artificial oxygen supply would not be necessary since the algal biomass can supply the bacterial O2 demand. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Optimization of Recovery of Nutrients from Pig Manure Slurry through Combined Microbial Fuel Cell and Microalgae Treatment

Microbial fuel cells (MFCs) and microalgae–bacteria consortia represent two renewable and promising technologies of growing interest that enable wastewater treatment while obtaining high-value-added products. This study integrates MFCs and microalgae production systems to treat animal slurry, aiming to remove and recover organic and inorganic components while generating energy and producing biomass. The MFCs effectively eliminated Chemical Oxygen Demand (COD), organic nitrogen, and a portion of the suspended solids, achieving a maximum voltage of 195 mV and a power density of 87.03 mW·m−2. After pre-treatment with MFCs, the slurry was diluted to concentrations of 10%, 50%, and 100% and treated with microalgae–bacteria consortia. The results showed a biomass production of 0.51 g·L−1 and a productivity of 0.04 g·L−1·day−1 in the culture fed with 10% slurry, with significant removal efficiencies: 40.71% for COD, 97.76% for N-NH4+, 39.66% for N-NO2−, 47.37% for N-NO3−, and 94.37% for P-PO4−3. The combination of both technologies allowed for obtaining a properly purified slurry and the recovery of nutrients in the form of bioelectricity and high-value biomass. Increasing the concentration of animal slurry to be treated is essential to optimize and scale both technologies.

Microalgal–Bacteria Biofilm in Wastewater Treatment: Advantages, Principles, and Establishment

The attached microalgal–bacterial consortium (microalgae–bacteria biofilm, MBBF) has been increasingly recognized in wastewater treatment for its superior pollutant removal efficiency, resilience to toxic substances, and improved harvesting performance. This review initially discusses the advantages of MBBFs compared to activated sludge and suspended microalgal–bacterial consortia. These advantages stem from the coexistence of pollutant removal pathways for the bacteria and microalgae in MBBFs, as well as the synergistic interactions between the microalgae and bacteria that enhance pollutant removal and resilience capabilities. Subsequently, the establishment of the MBBF system is emphasized, covering the establishment process, influencing factors of MBBF formation, and the utilization of photobioreactors. Lastly, the challenges associated with implementing MBBFs in wastewater treatment are deliberated. This study aims to present a detailed and comprehensive overview of the application of MBBFs for wastewater treatment and biomass production.

Microalgae–bacteria interaction: a catalyst to improve maize (Zea mays L.) growth and soil fertility

AbstractBiofertilisers harbouring living organisms hold allure due to their prospective favourable influence on plant growth, coupled with a diminished environmental footprint and cost-effectiveness in contrast to conventional mineral fertilisers. The purpose of the present study was to evaluate the capacity of a specific microalga (MACC-612, Nostoc linckia) biomass and plant growth-promoting bacteria (PGPB) separately and together to improve crop growth and promote soil health. The research used a factorial design within a completely randomised block framework, featuring four replications for three consecutive years across different fields. The experiment utilised three levels of microalga (control, 0.3 g/L of N. linckia, MACC-612, and 1 g/L of N. linckia, MACC-612) and three levels of bacterial strains (control, Azospirillum lipoferum and Pseudomonas fluorescens). The result demonstrated that the use of N. linckia and PGPB separately or jointly as soil treatment resulted in a substantial improvement in chlorophyll, plant biomass, soil humus, and nitrogen, depending on the environmental conditions of the years. The combined use of N. linckia and PGPB results in an improvement in dry leaf weight by 35.6–107.3% at 50 days after sowing (DAS) and 29.6–49.8% at 65 DAS, compared to the control group. Furthermore, the studies show that the synergistic application of N. linckia at 0.3 g/L, in conjunction with A. lipoferum, significantly improved total nitrogen and (NO3− + NO2−)-nitrogen, registering increases of 20.7–40% and 27.1–59.2%, respectively, during the study period. The most effective synergistic combination was identified through the application of 0.3 g/L of N. linckia along with A. lipoferum. Hence, application of biofertilisers through synergistic combinations of two or more microorganisms, such as microalgae and bacteria, holds promise in improving crop chlorophyll, growth, and soil nitrogen.

Freshwater microalgae Nannochloropsis limnetica for the production of β-galactosidase from whey powder

This study investigated the first-ever reported use of freshwater Nannochloropsis for the bioremediation of dairy processing side streams and co-generation of valuable products, such as β-galactosidase enzyme. In this study, N. limnetica was found to grow rapidly on both autoclaved and non-autoclaved whey-powder media (referred to dairy processing by-product or DPBP) without the need of salinity adjustment or nutrient additions, achieving a biomass concentration of 1.05–1.36 g L−1 after 8 days. The species secreted extracellular β-galactosidase (up to 40.84 ± 0.23 U L−1) in order to hydrolyse lactose in DPBP media into monosaccharides prior to absorption into biomass, demonstrating a mixotrophic pathway for lactose assimilation. The species was highly effective as a bioremediation agent, being able to remove > 80% of total nitrogen and phosphate in the DPBP medium within two days across all cultures. Population analysis using flow cytometry and multi-channel/multi-staining methods revealed that the culture grown on non-autoclaved medium contained a high initial bacterial load, comprising both contaminating bacteria in the medium and phycosphere bacteria associated with the microalgae. In both autoclaved and non-autoclaved DPBP media, Nannochloropsis cells were able to establish a stable microalgae–bacteria interaction, suppressing bacterial takeover and emerging as dominant population (53–80% of total cells) in the cultures. The extent of microalgal dominance, however, was less prominent in the non-autoclaved media. High initial bacterial loads in these cultures had mixed effects on microalgal performance, promoting β-galactosidase synthesis on the one hand while competing for nutrients and retarding microalgal growth on the other. These results alluded to the need of effective pre-treatment step to manage bacterial population in microalgal cultures on DPBP. Overall, N. limnetica cultures displayed competitive β-galactosidase productivity and propensity for efficient nutrient removal on DPBP medium, demonstrating their promising nature for use in the valorisation of dairy side streams.

Electroactive bacteria–algae biofilm coupled with siphon aeration boosts high-salinity wastewater purification: A pilot study focusing on performance and microbial community

Constructed wetland–microbial fuel cells (CW–MFC) and aeration technology are typically used for the treatment of mariculture wastewater with a low carbon/nitrogen ratio and high-salinity. However, salt inhibition limits their efficiency. Here, based on CW–MFC, an electroactive bacteria–algae biofilm and siphon aeration technology were employed in a pilot study to validate their technical and economic feasibility. The system yielded average removal efficiencies of 80.99 % ± 1.3 %, 92.59 % ± 3.13 %, 94.03 % ± 5.11 %, 97.38 % ± 3.62 %, and 95.95 % ± 2.59 %, respectively, for chemical oxygen demand, total phosphorus, total nitrogen, sulfamethoxazole, and Cu2+, with an average voltage of 354 ± 23 mV. Nitrification and denitrification bacteria Vicingus (12.52 %), Marinobacter (7.93 %), Muricauda (10.86 %), and Xanthomarina (13.62 %); extracellular respiratory bacteria Geobacteraceae (9.47 %) and Pseudomonas (2.54 %); and microalgae bacteria Pseudooceanicola (12.45 %) and Hoeflea (7.45 %) were significantly enriched. The energy consumption per ton of sewage treatment was 0.0045 kWh·m−3, representing 47.87 % lower costs than those related to traditional aeration. These results proved the feasibility of CW–MFC coupled with electroactive bacteria–algae biofilm and siphon aeration tidal flow technology for mariculture wastewater treatment.

Removal of veterinary antibiotics in swine manure wastewater using microalgae–bacteria consortia in a pilot scale photobioreactor

Scenedesmus almeriensis microalgae–bacteria consortia were evaluated for the removal of a mixture of tetracycline (TET), ciprofloxacin (CIP), and sulfadiazine (SDZ) from the real liquid fraction of pig slurry in a pilot scale photobioreactor. After 15 days of operation, the reactor was spiked with a mixture of 100μg/L of each antibiotic. The experiment ran for 20 additional days. From the liquid phase, antibiotic removal were 77 ± 5 %, 90 ± 14 %, and 60 ± 27 % for TET, CIP, and SDZ, respectively. The antibiotics found in the solid phase were 979 ± 382 ng/g for TET and 192 ± 69 ng/g for SDZ; CIP was not detected in the biomass. The parameters analyzed before and after antibiotic addition showed that the antibiotics did not have a negative effect on the reactor biomass. The removal efficiencies of the analyzed parameters were 64.6 ± 0.6 % for TOC, 56.9 ± 0.6 % for IC, 63.9 ± 0.6 % for TN, 88.6 ± 0.9 % for N-NH4+, 64.9 ± 0.6 % for N-NO3−, and 30.1 ± 0.3 % for P-PO43−. This study demonstrated the good performance of microalgae-based technology for swine manure wastewater treatment, not only in terms of organic matter and nutrient removal, but also regarding the removal of antibiotics. The mass balance analysis of the entire process is presented. Additionally, the present study is a validation of previous laboratory scale batch studies operating in a quasi-continuous mode on veterinary antibiotics (VA) removal efficiencies and kinetics.

Effect of Environmental Factors on Nitrite Nitrogen Absorption in Microalgae–Bacteria Consortia of Oocystis borgei and Rhodopseudomonas palustris

The effects of temperature, salinity, and illumination on the nitrite uptake rate of the microalgae–bacteria consortia of Oocystis borgei and Rhodopseudomonas palustris were investigated. The absorption rates of nitrite and the contribution rate of each component in the consortia under different temperatures (15, 20, 25, 30, 35 °C), illuminations (0, 15, 25, 35, 45 μmol·m−2·s−1), and salinities (0, 5, 15, 25, 35‰) were determined by stable isotope labeling technique. The single and combined effects of three environmental factors on nitrite uptake by the microalgae–bacteria consortia were analyzed using single-factor and orthogonal experiments. The single-factor experiment showed that the microalgae–bacteria consortia could absorb nitrite efficiently when the temperature, salinity, and illumination were 20~30 °C, 0~15‰, and 25~45 μmol·m−2·s−1, respectively, with the highest absorption rates were 2.086, 3.058, and 2.319 μg∙g−1∙h−1, respectively. The orthogonal experiment showed that the most efficient environmental conditions for nitrite uptake were 30 °C, 5‰ salinity, 35 μmol·m−2·s−1 illumination, and the rate of nitrite uptake by the microalgae–bacteria consortia was 3.204 μg∙g−1∙h−1. The results showed that the nitrite uptake rate of the O. borgei–R. palustris consortia was most affected by temperature, followed by salinity, and least by illumination. Under the same conditions, the nitrite absorption capacity of the microalgae–bacteria consortia was greater than that of single bacteria or algae, and R. palustris played a major role in the nitrite absorption of the consortia. The O. borgei and R. palustris consortia still maintain high nitrite absorption efficiency when the environment changes greatly, which has broad application prospects in the regulation and improvement of water quality in shrimp culture.

From waste-activated sludge to algae: a self-reliant cultivation process in photoreactors using saline conditions.

In this study, microalgae-bacteria (MB) systems using saline conditions (3 and 5% salinity) were built in order to use waste-activated sludge (AS) as raw material for cultivating lipid-rich microalgae. Algae were observed to be flourishing in 60 days of operation, which totally used the N and P released from the sludge biomass. A prominent improvement of lipid content in MB consortia was obtained under algae growth and salinity stimulation, which occupied 119-136 mg/g-SS rather than a low content of 12.1 mg/g-SS in AS. Lipid enrichment also brought a 3.1-3.3 times total heat release (THR) in the MB biomass. The marine spherical algae Porphyridium, as well as filamentous Geitlerinema, Nodularia, Leptolyngbya were found to be the main lipid producers and self-flocculated to 23.0% (R1) and 33.5% (R2) volume under the effect of residue EPS. This study had a big meaning in not only waste sludge reduction but also in manufacturing useful bioenergy products.

Kinetics of the removal mechanisms of veterinary antibiotics in synthetic wastewater using microalgae–bacteria consortia

Kinetics of the removal mechanisms of veterinary antibiotics in synthetic wastewater using microalgae–bacteria consortia

Base type determines the effects of nucleoside monophosphates on microalgae–bacteria symbiotic systems

Microalgae are promising sources of clean energy. Bioflocculation by cocultured bacteria is an effective way to harvest microalgae. As a key foundation for microorganisms, phosphorus is theoretically effective in shaping microalgae production and flocculation. In this study, the impacts of 23 nucleoside monophosphates on Auxenochlorella pyrenoidosa growth, lipid synthesis, and self-settlement and on the symbiotic bacterial system were investigated. Adenosine monophosphate was the most effective in enhancing microalgae development (2.14–3.16 × 108 cells/mL) and lipid production (average 10.48%) and resulted in a low settling velocity. Samples were divided into two groups, purine and pyrimidine feeding, according to a random forest analysis (OOB = 0%, p < 0.001). Purine feeding resulted in the highest soluble extracellular protein and polysaccharide secretion (p < 0.01). KEGG ortholog count prediction of functional genes related to biofilm formation was conducted using PICRUSt2, and significant upregulation (FC ≥ 1.77, p < 0.05) of the extracellular polymeric substance formation functional group was observed in the adenosine and guanosine treatments. The symbiotic bacterial community structure differed substantially between purine- and pyrimidine-feeding systems. In summary, these results indicated that the effect of nucleoside monophosphates on the microalgae–bacteria system is determined by the base type (purine or pyrimidine) rather than the molecular structure (cyclic or noncyclic).

Advances in sustainable wastewater treatment: Microalgal–bacterial consortia process, greenhouse gas reduction and energy recovery technologies

AbstractBecause of the low energy consumption of aeration, strong nutrient removal capacity, low greenhouse gas emissions and high resource recovery potential, the wastewater treatment process using microalgal–bacterial consortia is considered as an excellent alternative to the traditional activated sludge wastewater treatment process. In this review, the wastewater treatment process based on microalgal–bacterial consortia and its greenhouse gas emission reduction mechanism are introduced. The potential advantages and constraints of the process in carbon neutral wastewater treatment were highlighted and critically discussed. The environmental impact of wastewater treatment, the research progress of environment‐friendly treatment technologies and the challenges faced by integrating these technologies are discussed. However, the wastewater treatment process based on microalgae–bacteria consortia still needs to be studied. In the future, it is necessary to optimize the scheme for quantifying the environmental impact of wastewater treatment and further expand the recycling rate and cost value of wastewater resources.

Nitrogen removal from wastewater by an immobilized consortium of microalgae-bacteria in hybrid hydrogels.

The high content of nitrogen in wastewater brings some operational, technical, and economical issues in conventional technologies. The aim of this study was to evaluate the nitrogen removal by hybrid hydrogels containing consortium microalgae-nitrifying bacteria in the presence of activated carbon (AC) used as an adsorbent of inhibitory substances. Hybrid hydrogels were synthesized from polyvinyl alcohol (PVA), sodium alginate (SA), biomass (microalgae-nitrifying bacteria), and AC. The hybrid hydrogels were evaluated based on the change in ammonium (NH4), nitrate (NO3), and chemical demand of oxygen (COD) concentrations, nitrification rate, and other parameters during 72 h. Results indicated that NH4 removal was more effective for hydrogels without AC than with AC, without significant differences regarding consortium biomass concentration (5 or 16%), presenting final concentrations of 3.13 and 3.75 mg NH4/L for hydrogels with 5 and 16% of the biomass, respectively. Regarding NO3 production, hydrogels without AC reached concentrations of 25.9 and 39.77 mg NO3/L for 5 and 16% of the biomass, respectively, while treatments with AC ended with 2.17 and 1.37 mg NO3/L. This confirms that hydrogels can carry out the nitrification process and do not need AC to remove potential inhibitors. The best performance was observed for the hydrogel with 5% of biomass without AC with a nitrification rate of 0.43 mg N/g TSS·h.

Future bioenergy source by microalgae–bacteria consortia: a circular economy approach

Future sustainable approach of bioenergy production that uses microalgae–bacteria consortium to produce bioelectricity and biofuel for industrial and daily activities.

Model for Microalgae-Bacteria Systems with Nitrification and Photoinhibition

Microalgae-bacteria (MAB) systems are a useful technology for treating domestic wastewater. They combine the oxygen producing capability of microalgae with the chemical oxygen demand (COD) and total nitrogen degradation efficiency of aerobic bacteria in a synergistic manner. This work proposes a new mathematical model that incorporates two recently observed phenomena: photoinhibition during bacterial nitrification and heterotrophic growth of microalgae in the dark. The model is corroborated with experimental data, showing good prediction capabilities.

Pollutants removal, microbial community shift and oleic acid production in symbiotic microalgae–bacteria system

The functional interaction between microorganisms is key in symbiotic microalga–bacteria systems; however, evaluations of fungi and pathogenic microorganisms are not clear. In this study, the roles of three groups (i.e., microalgae–activated sludge (MAS), Microalgae, and activated sludge) in pollutant removal and biomass recovery were comparatively studied. The data implied that microalgal assimilation and bacterial heterotrophic degradation were the major approaches for degradation of nutrients and organic matter, respectively. According to 16S rRNA and internal transcribed spacer sequencing, the relative abundance of Rhodotorula increased remarkably, favoring nutrient exchange between the microalgae and bacteria. The abundances of two types of pathogenic genes (human pathogens and animal parasites) were reduced in the MAS system. The oleic acid content in the MAS system (51.2 mg/g) was 1.7 times higher than that in the Microalgae system. The results can provide a basis for practical application and resource utilization of symbiotic microalgae–bacteria systems.

Influence of supplementary carbon on reducing the hydraulic retention time in microalgae-bacteria (MaB) treatment of municipal wastewater

Real municipal wastewater was treated using microalgae and bacteria (MaB) flocs with the goal to achieve the European standards (EUS91) in less than 2 days of hydraulic retention time (HRT). The pH in the control series (CS) was allowed to increase freely. In the inorganic carbon supplement (ICS) series, the pH was maintained below 8.0 by means of CO2 injection. The presence of CO2 regulated the nitrogen profiles, but the total removal did not improve. Nitrification was stronger and advanced more when CO2 was applied during 2 days of HRT with an average ammonium oxidation rate of 40.5 ± 4.9 %. The residual phosphate and nitrogen oxides were assimilated on the third day of treatment. Balancing the organic carbon (COD:NH4–N ratio of 15.9) suppressed the autotrophic activities (nitrification) and improved the biomass assimilation significantly. Batch experiments with balanced organic carbon could remove nitrogen and phosphorus with rates of 43.1 ± 5.1 mg N L−1 d−1 (88.3 ± 13.9 %) and 6.21 ± 0.07 mg PO4–P L−1 d−1 (98.2 ± 1.6 %) after 28 hours. Our results show that balanced MaB culture can satisfy the EUS91 limits within approximately 24 hours of treatment.

Optimization of Microalgae–Bacteria Consortium in the Treatment of Paper Pulp Wastewater

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.

Towards a mechanistic understanding of microalgae-bacteria interactions: integration of metabolomic analysis and computational models.

Interactions amongst marine microalgae and heterotrophic bacteria drive processes underlying major biogeochemical cycles and are important for many artificial systems. These dynamic and complex interactions span the range from cooperative to competitive, and it is the diverse and intricate networks of metabolites and chemical mediators that are predicted to principally dictate the nature of the relationship at any point in time. Recent advances in technologies to identify, analyze, and quantify metabolites have allowed for a comprehensive view of the molecules available for exchange and/or reflective of organismal interactions, setting the stage for development of mechanistic understanding of these systems. Here, we (i) review the current knowledge landscape of microalgal-bacterial interactions by focusing on metabolomic studies of selected, simplified model systems; (ii) describe the state of the field of metabolomics, with specific focus on techniques and approaches developed for microalga-bacterial interaction studies; and (iii) outline the main approaches for development of mathematical models of these interacting systems, which collectively have the power to enhance interpretation of experimental data and generate novel testable hypotheses. We share the viewpoint that a comprehensive and integrated series of -omics approaches that include theoretical formulations are necessary to develop predictive and mechanistic understanding of these biological entities.

Urban wastewater treatment by microalgae, bacteria and microalgae–bacteria system (Laboratory-scale study)

ABSTRACT Besides existing methods of urban wastewater treatment processing (WWTP), microalgae culture systems are one of the environmental friendly methods for improving urban wastewater treatment. In this research, the removal efficiency of N-nitrate and orthophosphate from urban wastewater were investigated using free and immobilized Chlorella vulgaris microalgae, Pseudomonas fluorescens bacteria and symbiosis of microalgae with bacteria. Pseudomonas fluorescens bacteria are a group of bacteria that stimulates plant growth. The performance of immobilized microalgae and immobilized bacteria in nitrate removal was better than that in free microalgae and free bacteria. The results showed that the maximum removal efficiency of N-NO3 was 87.06% in immobilized microalgae (MIM). In removing orthophosphate, free microalgae-bacteria (MBFr) and immobilized microalgae—bacteria (MBIm) had higher performance among other treatments with removal efficiency of 89.64% and 86.38%, respectively. According to significant reductions of orthophosphate on the second day of measurements, the residence time could be considered about two days.