Microalgal-bacterial Consortia Research Articles

Cultivation of flocculated microalgal–bacterial consortia using fluidised carriers for wastewater treatment and renewable energy production

Microalgal–bacterial consortia (MBC) and microalgal consortia (MC) were cultivated with primary and final treated wastewaters, respectively, using a fluidised carrier. This study determines the main factors and operations required for flocculating suspended MBC (SMBC) and MC (SMC) in cultures. The flocculated SMBC and SMC with good settleability require the detachment of thickened MBC or MC on the carrier and suppressed SMBC and SMC formation by the original MBC and MC grown in the culture. Flocculation was achieved by controlling the carrier and culture replacements. A carrier replacement ratio of 0.04 d−1 and a culture replacement ratio of 0.95 d−1 minimised the dissolved organic carbon (15.3 mg-C/L) and SMBC residue (7.3 mg/L). Thus, treating primary treated wastewater with MBC formed using fluidised carriers is a promising strategy, enabling the use of whole cells in MBC for renewable energy production.

Conventional activated sludge vs. photo-sequencing batch reactor for enhanced nitrogen removal in municipal wastewater: Microalgal-bacterial consortium and pathogenic load insights

Municipal wastewater treatment plants are mostly based on traditional activated sludge (AS) processes. These systems are characterised by major drawbacks: high energy consumption, large amount of excess sludge and high greenhouse gases emissions. Treatment through microalgal-bacterial consortia (MBC) is an alternative and promising solution thanks to lower energy consumption and emissions, biomass production and water sanitation. Here, microbial difference between a traditional anaerobic sludge (AS) and a consortium-based system (photo-sequencing batch reactor (PSBR)) with the same wastewater inlet were characterised through shotgun metagenomics. Stable nitrification was achieved in the PSBR ensuring ammonium removal > 95 % and significant total nitrogen removal thanks to larger flocs enhancing denitrification. The new system showed enhanced pathogen removal, a higher abundance of photosynthetic and denitrifying microorganisms with a reduced emissions potential identifying this novel PSBR as an effective alternative to AS.

Native microalgal-bacterial consortia from the Ecuadorian Amazon region: an alternative to domestic wastewater treatment.

In low-middle income countries (LMIC), wastewater treatment using native microalgal-bacterial consortia has emerged as a cost-effective and technologically-accessible remediation strategy. This study evaluated the effectiveness of six microalgal-bacterial consortia (MBC) from the Ecuadorian Amazon in removing organic matter and nutrients from non-sterilized domestic wastewater (NSWW) and sterilized domestic wastewater (SWW) samples. Microalgal-bacterial consortia growth, in NSWW was, on average, six times higher than in SWW. Removal rates (RR) for NH4 +- N and PO4 3--P were also higher in NSWW, averaging 8.04 ± 1.07 and 6.27 ± 0.66mgL-1 d-1, respectively. However, the RR for NO3 - -N did not significantly differ between SWW and NSWW, and the RR for soluble COD slightly decreased under non-sterilized conditions (NSWW). Our results also show that NSWW and SWW samples were statistically different with respect to their nutrient concentration (NH4 +-N and PO4 3--P), organic matter content (total and soluble COD and BOD5), and physical-chemical parameters (pH, T, and EC). The enhanced growth performance of MBC in NSWW can be plausibly attributed to differences in nutrient and organic matter composition between NSWW and SWW. Additionally, a potential synergy between the autochthonous consortia present in NSWW and the native microalgal-bacterial consortia may contribute to this efficiency, contrasting with SWW where no active autochthonous consortia were observed. Finally, we also show that MBC from different localities exhibit clear differences in their ability to remove organic matter and nutrients from NSWW and SWW. Future research should focus on elucidating the taxonomic and functional profiles of microbial communities within the consortia, paving the way for a more comprehensive understanding of their potential applications in sustainable wastewater management.

Optimizing aeration intensity to enhance self-flocculation in algal-bacterial symbiosis systems

Effectuating optimal wastewater treatment via algae-bacterial symbiosis (ABS) systems necessitates the precise selection of aeration intensity. This study pioneers an in-depth investigation into the interplay of aeration intensity on the microalgal-bacterial consortia's self-flocculation efficacy and the overall treatment performance within ABS systems. The research provides evidence for a direct association between aeration intensity and biomass proliferation, indicating enhanced pollutant removal efficiency with escalated intensities (1.0 and 1.5 L min−1), though the variance lacks statistical significance. The peak self-flocculation efficacy of the microalgal-bacterial consortium (82.39% at 30 min) was manifested at an aeration intensity of 1.0 L min−1. The meticulous analysis of biomass properties showed the complexity of self-flocculation capacity in the consortium, which involves a dynamic interplay of several pivotal factors, including floc size, zeta potential, and EPS content. In situations where these factors pose conflicting influences, the determining factor emerges as the dominant influencer. In this study, the optimal aeration intensity was identified as 1 L min−1, shedding light on the critical threshold for ABS system operation. This study not only enriches the understanding of microalgal-bacterial wastewater treatment mechanisms but also fosters innovative strategies to enhance the performance of such systems.

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.

Bioelectricity production and shortcut nitrogen removal by microalgal-bacterial consortia using membrane photosynthetic microbial fuel cell

Membrane photosynthetic microbial fuel cell (MPMFC) utilizes O2, NO3− and NO2− as cathodic electron acceptors, enabling simultaneous treatment of nitrogen, CO2 and organic carbon in the cathode compartment. In this work, development of a novel cathodic process with in situ nitritation via microalgal photosynthesis during the light period is reported for achieving shortcut nitrogen removal (SNR) from ammonium-rich wastewater. Moreover, a tubular low-cost ceramic membrane was used to separate and recycle the microalgal-bacterial biomass to the cathode compartment during the continuous operation. The influence of NH4+ concentration and ratio of chemical oxygen demand to total nitrogen on the MPMFC performance was examined. Denitritation under dark and anoxic conditions occurred due to denitrifying bacteria (DNB) subsequent to nitritation under light and aerobic conditions by ammonia-oxidizing bacteria (AOB) in the consortia. Final concentrations of NH4+ and NO2− in the effluent of 0.10 mg NH4+-L−1 and 0.02 mg NO2−-L−1, respectively, were obtained using MPMFC which resulted in a nitrogen removal efficiency of 99 ± 0.5%. The maximum electricity production achieved using the MPMFC was 56 ± 0.1 mA. This study demonstrated that combining microalgal photosynthesis, nitritation and denitritation in the cathode compartment of MPMFC is advantageous for avoiding the cost due to external aeration and organic carbon source necessary for ammonium removal as well as utilization of NO2− or NO3− as an electron acceptor.

Microalgal-Bacterial Consortia as Future Prospect in Wastewater Bioremediation, Environmental Management and Bioenergy Production.

In the recent years, microalgae have captured researchers' attention as the alternative feedstock for various bioenergy production such as biodiesel, biohydrogen, and bioethanol. Cultivating microalgae in wastewaters to simultaneously bioremediate the nutrient-rich wastewater and maintain a high biomass yield is a more economical and environmentally friendly approach. The incorporation of algal-bacterial interaction reveals the mutual relationship of microorganisms where algae are primary producers of organic compounds from CO2, and heterotrophic bacteria are secondary consumers decomposing the organic compounds produced from algae. This review would provide an insight on the challenges and future development of algal-bacterial consortium and its contribution in promoting a sustainable route to greener industry. It is believed that microalgal-bacterial consortia will be implemented in the near-future for sub-sequential treatment of wastewater bioremediation, bioenergy production and CO2 fixation, promoting sustainability and making extraordinary advancement in life sciences sectors.

Microalgal-bacterial consortia unveil distinct physiological changes to facilitate growth of microalgae.

Physiological changes that drive the microalgal-bacterial consortia are poorly understood so far. In the present novel study, we initially assessed five morphologically distinct microalgae for their ability in establishing consortia in Bold's basal medium with a bacterial strain, Variovorax paradoxus IS1, all isolated from wastewaters. Tetradesmus obliquus IS2 and Coelastrella sp. IS3 were further selected for gaining insights into physiological changes, including those of metabolomes in consortia involving V. paradoxus IS1. The distinct parameters investigated were pigments (chlorophyll a, b, and carotenoids), reactive oxygen species (ROS), lipids and metabolites that are implicated in major metabolic pathways. There was a significant increase (>1.2-fold) in pigments, viz., chlorophyll a, b and carotenoids, decrease in ROS and an enhanced lipid yield (>2-fold) in consortia than in individual cultures. In addition, the differential regulation of cellular metabolites such as sugars, amino acids, organic acids and phytohormones was distinct among the two microalgal-bacterial consortia. Our results thus indicate that the selected microalgal strains, T. obliquus IS2 and Coelastrella sp. IS3, developed efficient consortia with V. paradoxus IS1 by effecting the required physiological changes, including metabolomics. Such microalgal-bacterial consortia could largely be used in wastewater treatment and for production of value-added metabolites.

Advances in Studies on Nitrogen and Phosphorus Removal by Microalgal-Bacterial Consortia

With the development of life and industry, the nutrients in sewage increased gradually. The emerging symbiotic system of algal and bacteria has remarkable effect in removing nutrients such as nitrogen and phosphorus. In this paper, the influence of nitrogen and phosphorus on bacteria-algal consortia and the absorption mechanism of nitrogen and phosphorus by the interaction of bacteria-algal consortia were analyzed, and a variety of methods for studying bacteria-algal consortia were summarized, mainly using isotope tracer technology to study the research results of bacteria and algae absorbing nitrogen and phosphorus in water. This method is of great significance for analyzing the mechanism of the treatment of nitrogen and phosphorus by the bacterial-algal symbiosis system from the microscopic point of view.

MICROALGAL-BACTERIAL CONSORTIA: AN ALLURING AND NOVEL APPROACH FOR DOMESTIC WASTEWATER TREATMENT

The algal-bacterial process has received more attention in the present scenario as a new low-cost method towards pollutant removal from wastewater because symbiotic relationship between algae and bacteria is efficient when compared to traditional secondary treatments. The present work evaluated the optimum concentration of microalgal-bacterial consortia for significant reductions in physicochemical parameters of raw domestic wastewater. In the study, three different concentrations (20%, 30% and 40%) of microalgal-bacterial consortia were studied at 8 hours and 16 hours HRT. Among the different concentrations of consortia studied, 30% consortia gave maximum removal efficiency at both the HRTs. The maximum removal efficiency of phosphate, ammonia, BOD and COD was about 99.79%, 94.85%, 89.02% and 88.96%, respectively, at 8 hours HRT. However, at 16 hours, HRT maximum removal efficiency observed was 97.40%, 94.05%, 83.52% and 88.40% for phosphate, ammonia, BOD and COD respectively. The study depicts that microalgal-bacterial consortia can efficiently remediate nutrients and organic matter from domestic wastewater in both cases when sunlight was ample and even with minimal / no sunlight; hence this system can work effectively throughout the day with much lesser HRT and higher removal efficiency.

Biocontrol of acute hepatopancreatic necrosis disease (AHPND) in shrimp using a microalgal-bacterial consortium

Co-culturing microalgae Picochlorum strain S1b with bacterium isolated from non-axenic S1b cultures (i.e., Labrenzia sp. strain #8, Muricauda sp. strain #50, or Arenibacter sp. strain #61) can provide growth inhibitory effects against Vibrio harveyi and/or Vibrio campbellii. To determine whether this strategy can also provide growth inhibitory effects against Vibrio parahaemolyticus and thus help control acute hepatopancreatic necrosis disease (AHPND) in shrimp, this study compared the ability of various microalgal-bacterial consortia (S1b+#8, S1b+#50, S1b+#61, and S1b+#8, #50, #61) to inhibit the growth of V. parahaemolyticus. The challenge tests were then performed to determine whether the identified microalga-bacterial consortium can increase the survival of shrimp infected with AHPND-causing V. parahaemolyticus. The results revealed that only S1b+#8, #50, #61 (S1b+all) significantly inhibited V. parahaemolyticus growth. For this consortium, both feeding (0.8% of shrimp body weight/day) and immersion (10–100 mL microalgal-bacterial co-culture/30 L tank water/day) methods conferred protective effects, thereby demonstrating that the S1b+all has the potential to improve AHPND control. Of the two methods, feeding was found to be more suitable for the outdoor cultivation of juvenile shrimp, whereas immersion was found to be suitable for the indoor cultivation of shrimp postlarvae.

Mechanisms of pharmaceutical and personal care product removal in algae-based wastewater treatment systems

The widespread distribution of pharmaceuticals and personal care products (PPCPs), particularly in the built environment, has led to increased concern about their effects on both human and ecosystem health. In this research, we investigated the role of algae species Scenedesmus obliquus and Chlorella vulgaris in governing PPCP transfer and transformation mechanisms in algae-containing environments. Lab-scale algal bioreactors were created under various conditions of light, water matrix, and sterilization method to isolate and elucidate reaction mechanisms affecting carbamazepine, ibuprofen, gemfibrozil, and triclosan. The parent compounds and their potential transformation products were analyzed in both the water and algae phases. The results showed that ibuprofen was primarily biotransformed due to synergistic relationships between the algae and the bacteria. Ibuprofen biotransformation products tentatively identified as hydroxy-ibuprofen, carboxy-ibuprofen, and 4-isobutylcatechol were detected in several samples. In all the reactors exposed to light, triclosan underwent both phototransformation and biotransformation. Triclosan biotransformation took place in Scenedesmus obliquus, as demonstrated by the presence of triclosan-O-sulfate in the algae extracts. No evidence of significant carbamazepine and gemfibrozil transfer or transformation was observed under the experimental conditions tested. These results suggest that microalgal–bacterial consortia can facilitate PPCP transformation in algae-based passive water treatment systems.

Wastewater polishing by consortia of Chlorella vulgaris and activated sludge native bacteria

The increase of human population and anthropogenic activities has resulted in an excessive discharge of wastes into water bodies, contributing to nutrients enrichment and consequent degradation of aquatic environments and freshwater resources. The need for cost-effective systems able to reduce nutrients concentration in wastewaters is therefore a major concern. Microalgal-bacterial consortia can be effectively applied in wastewater polishing, since co-cultivation of these microorganisms can promote mutual growth and nutrients removal from wastewaters. In this study, dual-species cultures of the microalga Chlorella vulgaris and a bacterium isolated from a municipal wastewater treatment plant (Enterobacter asburiae, Klebsiella sp. or Raoultella ornithinolytica) were performed. Studying these consortia aimed the evaluation of their potential in nutrients (nitrogen, phosphorus and chemical oxygen demand) removal from a synthetic medium that mimics a secondary-treated effluent (nitrogen, phosphorus and chemical oxygen demand loads of about 45 mg N L−1, 10 mg P L−1 and 300 mg O2 L−1, respectively). The results have shown that the consortia containing E. asburiae and R. ornithinolytica have significantly improved C. vulgaris growth: when in single cultures maximum cell concentration achieved by C. vulgaris was (8.27 ± 0.79) × 106 cells per mL, whereas in these consortia maximum cell concentrations achieved by C. vulgaris were (19.8 ± 2.0) × 106 and (14.4 ± 2.3) × 106 cells per mL, respectively. The three studied consortia have also contributed to higher nutrients removal, since the time required to achieve the limits in discharged effluents (established by European Union legislation) was reduced to at least half of the value determined for the single C. vulgaris culture. Due to the effectiveness demonstrated by the studied consortia, these microalgal-bacterial systems should be considered as a viable approach for application in the tertiary treatment step of wastewater treatment processes.

Microalgal-Bacterial Consortium in Polyaromatic Hydrocarbon Degradation of Petroleum Based Effluent

The recurrent and indiscriminate discharge of flow stations' crude oil effluent has led to an increased polyaromatic hydrocarbons (PAHs) level in the environment. PAHs are high-priority environmental pollutants of significant human health concerns, thus considerable effort has been made in this study to biodegrade these PAHs using microalgalbacterial consortia. Crude oil effluent samples collected from the saver pit at Egbaoma flow station in the Niger Delta region of Nigeria were analysed biochemically and microbiologically. Three species of bacteria and two species of microalgae isolated, characterized and screened emerged as best hydrocarbon utilizers. The consortia comprised of Chlorella minutissimma and Aphanocapsa sp. as microalgae inoculants, while Citrobacter sp. SB9, Pseudomonas aeruginosa SA3 and Bacillus subtilis SA7 as bacterial inoculants. Growth dynamics, pH and degradation of the effluents' PAH content were analyzed for a period of ten days. Consortium BCC (bacteria inoculants and Chlorella minutissimma), BCCA (all inoculants) and BCA (bacteria inoculants and Aphanocapsa sp.) had PAH degradation percentage of 92.09%, 67.76% and 47.19% and optical density (OD) of 0.1255°A, 0.0669°A and 0.0703°A from an initial OD of 0.0126°A respectively. Only BCA had an acidic pH after ten days. Effective synergism and excellent PAH degradation is achievable and highly recommendable with microalgal-bacterial consortium yet its success is highly dependent on the consortium assembling, therefore, proper selection of the microbes for biodegradation is paramount to the success and efficiency of the degradation process.

Mixotrophic metabolism of Chlorella sorokiniana and algal-bacterial consortia under extended dark-light periods and nutrient starvation.

Microalgae harbor a not fully exploited industrial and environmental potential due to their high metabolic plasticity. In this context, a better understanding of the metabolism of microalgae and microalgal-bacterial consortia under stress conditions is essential to optimize any waste-to-value approach for their mass cultivation. This work constitutes a fundamental study of the mixotrophic metabolism under stress conditions of an axenic culture of Chlorella sorokiniana and a microalgal-bacterial consortium using carbon, nitrogen, and phosphorous mass balances. The hydrolysis of glucose into volatile fatty acids (VFA) during dark periods occurred only in microalgal-bacterial cultures and resulted in organic carbon removals in the subsequent illuminated periods higher than in C. sorokiniana cultures, which highlighted the symbiotic role of bacterial metabolism. Acetic acid was preferentially assimilated over glucose and inorganic carbon by C. sorokiniana and by the microalgal-bacterial consortium during light periods. N-NH4 (+) and P-PO4 (-3) removals in the light stages decreased at decreasing duration of the dark stages, which suggested that N and P assimilation in microalgal-bacterial cultures was proportional to the carbon available as VFA to produce new biomass. Unlike microalgal-bacterial cultures, C. sorokiniana released P-PO4 (-3) under anaerobic conditions, but this excretion was not related to polyhydroxybutyrate accumulation. Finally, while no changes were observed in the carbohydrate, lipid and protein content during repeated extended dark-light periods, nutrient deprivation boosted both C-acetate and C-glucose assimilation and resulted in significantly high biomass productivities and carbohydrate contents in both C. sorokiniana and the microalgal-bacterial cultures.