Algae-bacteria Consortia Research Articles

Urban wastewater treatment at ambient conditions using microalgae-bacteria consortia in a membrane high-rate algal pond (MHRAP): The effect of hydraulic retention time and influent strength

The effects of hydraulic retention time (HRT) and influent wastewater strength on microalgae-bacteria performance were studied in two sets of experiments in a 6-day biomass retention time membrane high-rate algal pond (MHRAP) pilot plant to assess its pollutants removal potential. In the first set of experiments, the MHRAP was continuously fed with effluent from primary settling and operated at 6-, 4- and 2-days HRT and in the second set, the MHRAP was operated at 4-, 2-, and 1-day HRT using pre-treatment effluent. Results showed a complex interaction between algae-bacteria consortium, ambient conditions and MHRAP operation. In set 1, the highest total nitrogen (T-N) and total phosphorus (T-P) removal efficiencies were reached with 6-day HRT (23.6±0.6 % and 32±4 %, respectively), partially due to free ammonia nitrogen stripping and phosphorus precipitation, because of abiotic factors, which reduces the activity of nitrite-oxidizing bacteria and led to partial-nitrification. On the other hand, the 4 and 2-day HRT T-N and T-P removal efficiencies were reduced (below 10 % and 5 %, respectively) because the abiotic factors limited the physicochemical processes, and less biomass was taken up. In set 2, a suitable equilibrium between the microalgae and bacterial communities at 2-days HRT achieved high T-N (91±5 %) and T-P (71±8 %) removal efficiencies. Mass balances indicated that the nitrogen was mostly removed by nitrification-denitrification (87 % of T-N) and T-P predominant removal mechanism was precipitation. The COD removal efficiencies were higher than 86 % in both sets, since the particulate COD and colloids were removed by ultrafiltration. The obtained results showed that MHRAP technology would allow reducing COD and nutrient loads in the effluent under certain operating conditions, demonstrating the potential for resource recovery and wastewater treatment of microalgae-bacteria consortia.

N-acyl homoserine lactones (AHLs) enhanced removal of cadmium and other pollutants by algae-bacteria consortia

Signal transduction is an important mode of algae-bacteria interaction, in which bacterial quorum sensing (QS) may affect microalgal growth and metabolism. Currently, little is known whether acyl homoserine lactones (AHLs) released by bacteria can affect the pollutant removal by algae-bacteria consortia (ABC). In this study, we constructed ABC using Chlorella vulgaris (Cv) with two AHLs-producing bacteria and investigated their performance in the removal of multiple pollutants, including chemical oxygen demand (COD), total nitrogen (TN), phosphorus (P), and cadmium (Cd). The AHLs-producing bacteria, namely Agrobacterium sp. (Ap) and Ensifer adherens (Ea), were capable of forming a symbiosis with C. vulgaris. Consortia of Cv and Ap with ratio of 2:1 (Cv2-Ap1) showed the optimal growth promotion and higher removal of Cd, COD, TN, and P compared to the C. vulgaris monoculture. Cv2-Ap1 ABC removed 36.1–47.5% of Cd, 94.5%–94.6% COD, 37.1%–56.0% TN, and 90.4%–93.5% P from the culture medium. In addition, increase of intracellular neutral lipids and extracellular protein, as well as the types of functional groups on cell surface contributed to Cd removal and tolerance in the Cv2-Ap1 ABC. Six AHLs were detected in the Cv2-Ap1 culture. Among these, 3OC8-HSL and 3OC12-HSL additions promoted the ABC growth and enhanced their Cd accumulation. These findings may contribute to further understanding of AHL-mediated communication between algae and bacteria and provide support bioremediation efforts of metal-containing wastewater.

Microbial succession and enrichment of antibiotic resistance genes during algal-bacterial biofilm purification of aquaculture wastewater

This study involved the establishment of algal-bacterial biofilms on the surface of carbon fiber-based artificial aquatic plants, utilizing algal-bacterial symbiosis for the purification of aquaculture wastewater. The algae-bacteria consortium exhibited strong photosynthetic activity, as indicated by the chlorophyll a + b content (0.918 ± 0.029 mg/g carbon fiber (CF)). Particularly, during the initial 7 days, algal-bacterial biofilm displayed robust water purification activity and capacity, with a significant reduction in total phosphorus (TP) of 39.44 % ± 2.43 % observed. The microbial community of the biofilm was diverse, primarily dominated by Proteobacteria, Cyanobacteria, Actinomycetota, and Planctomycetota. Among these, Proteobacteria were in the highest abundance ranging from 39.18 % to 40.61 %. Changes in Cyanobacteria, driven by nutrient level alterations, not only impacted species abundance but also posed a risk of promoting the spread of antibiotic resistance genes (ARGs). Through the complex interactions among biological communities, 15 types of ARGs have been enriched on the algal-bacterial biofilm, among which Multidrug, Bacitracin, Aminoglycoside, and Glycopeptid have a higher abundance. Contigs and network analysis indicate that Nannocystis, Sphingorhabdus, and Polynucleobacter are the key hosts and it is found that their abundance will increase during the purification of water quality by the algal-bacterial biofilm. This study highlighted the risk of ARG transmission in aquaculture effluent treatment with algal-bacterial biofilms.

Algae-Mediated Removal of Prevalent Genotoxic Antibiotics: Molecular Perspective on Algae-Bacteria Consortia and Bioreactor-Based Strategies.

Antibiotic pollution poses a potential risk of genotoxicity, as antibiotics released into the environment can induce DNA damage and mutagenesis in various organisms. This pollution, stemming from pharmaceutical manufacturing, agriculture, and improper disposal, can disrupt aquatic ecosystems and potentially impact human health through the consumption of contaminated water and food. The removal of genotoxic antibiotics using algae-mediated approaches has gained considerable attention due to its potential for mitigating the environmental and health risks associated with these compounds. The paper provides an in-depth examination of the molecular aspects concerning algae and bioreactor-driven methodologies utilized for the elimination of deleterious antibiotics. The molecular analysis encompasses diverse facets, encompassing the discernment and profiling of algae species proficient in antibiotic degradation, the explication of enzymatic degradation pathways, and the refinement of bioreactor configurations to augment removal efficacy. Emphasizing the significance of investigating algal approaches for mitigating antibiotic pollution, this paper underscores their potential as a sustainable solution, safeguarding both the environment and human health.

Highly efficient and rapid removal of Malathion using non-aerated algae bacteria consortia: Performance, kinetic, and microbial mechanisms

The frequent use of pesticides in human activities introduce Malathion into water， which caused serious environmental pollutants. However, the treatment of these wastewaters is expensive and inefficiency. In this study, two photo-sequencing batch reactors (PSBRs) were established to treat Malathion-containing wastewater using algae bacteria consortia (ABC) in aerated (R1) and non-aerated (R2) conditions, respectively. The removal rates of Malathion by ABC in R1 and R2 after stabilization were 83.6 % and 71.9 %, respectively. The microbial community analysis results indicated that Burkholderia was the dominant population in ABC, which was response for the main Malathion degradation. Furthermore, the investigation of degradation pathways of Malathion discovered that the ABC converted Malathion into inorganic phosphorus. The conversion rates of inorganic phosphorus in the two reactors were 16.9 % and 21.6 %. The results demonstrated that non-aerated ABC have a strong potential adaption on Malathion stress and can removal Malathion from wastewater economically and efficiently.

Treatment of atrazine-containing wastewater by algae-bacteria consortia: Signal transmission and metabolic mechanism

Atrazine is a toxic endocrine disruptor. Biological treatment methods are considered to be effective. In the present study, a modified version of the algae-bacteria consortia (ABC) was established and a control was simultaneously set up to investigate the synergistic relationship between bacteria and algae and the mechanism by which atrazine is metabolized by those microorganisms. The total nitrogen (TN) removal efficiency of the ABC reached 89.24% and the atrazine concentration was reduced to below the level recommended by the Environment Protection Agency (EPA) regulatory standards within 25 days. The protein signal released from the extracellular polymeric substances (EPS) secreted by the microorganisms triggered the resistance mechanism of the algae, and the conversion of humic acid to fulvic acid and electron transfer constituted the synergistic mechanism between the bacteria and algae. The mechanism by which atrazine is metabolized by the ABC mainly consists of hydrogen bonding, H–pi interactions, and cation exchange with atzA for hydrolysis, followed by a reaction with atzC for decomposition to non-toxic cyanuric acid. Proteobacteria was the dominant phylum for bacterial community evolution under atrazine stress, and the analysis revealed that the removal of atrazine within the ABC was mainly dependent on the proportion of Proteobacteria and the expression of degradation genes (p < 0.01). EPS played a major role in the removal of atrazine within the single bacteria group (p < 0.01).

Effect of the N-hexanoyl-L-homoserine Lactone on the Carbon Fixation Capacity of the Algae-Bacteria System.

Algae-bacteria systems are used widely in wastewater treatment. N-hexanoyl-L-homoserine lactone (AHL) plays an important role in algal-bacteria communication. However, little study has been conducted on the ability of AHLs to regulate algal metabolism and the carbon fixation ability, especially in algae-bacteria system. In this study, we used the Microcystis aeruginosa + Staphylococcus ureilyticus strain as a algae-bacteria system. The results showed that 10 ng/L C6-HSL effectively increased the chlorophyll-a (Chl-a) concentration and carbon fixation enzyme activities in the algae-bacteria group and algae group, in which Chl-a, carbonic anhydrase activity, and Rubisco enzyme increased by 40% and 21%, 56.4% and 137.65%, and 66.6% and 10.2%, respectively, in the algae-bacteria group and algae group, respectively. The carbon dioxide concentration mechanism (CCM) model showed that C6-HSL increased the carbon fixation rate of the algae-bacteria group by increasing the CO2 transport rate in the water and the intracellular CO2 concentration. Furthermore, the addition of C6-HSL promoted the synthesis and secretion of the organic matter of algae, which provided biogenic substances for bacteria in the system. This influenced the metabolic pathways and products of bacteria and finally fed back to the algae. This study provided a strategy to enhance the carbon fixation rate of algae-bacteria consortium based on quorum sensing.

Insight into the formation mechanism of algal biofilm in soy sauce wastewater

Microalgal-biofilm-based wastewater treatment refers to a microalgae-dominated biofilm community in non-axenic systems, in which co-existing bacteria and microbial extracellular polymeric substances (EPS) are crucial for the formation of algal biofilm. However, algae-bacteria consortium biofilm-forming mechanism has rarely been studied in wastewaters including soy sauce wastewater (SW). In this study, we conducted algal biofilm cultivation in raw SW (RSW) and sterilized SW (SSW), and determined the characteristics of algal biofilm and its EPS in the two SW treatments. The results demonstrated that the co-existing bacteria in the algal biofilm system significantly enhanced attached biomass and nutrient removal from RSW, compared to SSW without bacteria. The enhancement may be attributed to EPS excreted by dominated Acinetobacter and Comamonas (both Proteobacteria) in the co-existing bacteria community. The algae-bacteria consortium from algal biofilm in RSW excreted the contents of relatively high tightly bound EPS (TB-EPS) and its proteins (TB-PN), which were conducive to forming the algal biofilm. The high TB-EPS content was related to soluble microbial by-product-like substances (mainly proteins), and its high TB-PN content was mainly caused by the increases in hydrophobic glycine and serine contents for stable biofilm formation. Based on these results, we enhanced our understanding of the formation mechanism of algal biofilm in SW remediation, which provided the theoretical basis for biofilm formation by algae-bacteria synergism.

Respirometric assessment of bacterial kinetics in algae-bacteria and activated sludge processes

Algae-bacteria (AB) consortia can be exploited for effective wastewater treatment, based on photosynthetic oxygenation to reduce energy requirements for aeration. While algal kinetics have been extensively evaluated, bacterial kinetics in AB systems are still based on parameters taken from the activated sludge models, lacking an experimental validation for AB consortia. A respirometric procedure was therefore proposed, to estimate bacterial kinetics in both activated sludge and AB, under different conditions of temperature, pH, dissolved oxygen, and substrate availability. Bacterial activities were differently influenced by operational/environmental conditions, suggesting that the adoption of typical activated sludge parameters could be inadequate for AB modelling. Indeed, respirometric results show that bacteria in AB consortia were adapted to a wider range of conditions, compared to activated sludge, confirming that a dedicated calibration of bacterial kinetics is essential for effectively modelling AB systems, and respirometry was proven to be a powerful and reliable tool to this purpose.

Piggery wastewater treatment with algae-bacteria consortia: Pilot-scale validation and techno-economic evaluation at farm level

The efficiency of an outdoor pilot-scale raceway pond treating the wastewaters generated by a large-scale piggery farm in Northern Italy was evaluated. The biomass productivity over 208 days of experimentation was 10.7 ± 6.5 g TSS·m−2·d−1, and ammoniacal nitrogen, orthophosphate, and COD average removal efficiencies were 90%, 90%, and 59%, respectively. Results were used to perform a comprehensive techno-economic analysis for integrating algae-based processes in farms of different sizes (100–10000 pigs). The amount of N disposed of on agricultural land could be reduced from 91% to 21%, increasing the fraction returned to the atmosphere from 2.4% to 63%, and the fraction in the biomass from 6.2% to 16%. For intensive farming, the release of 110 t N·ha−1·y−1 contained in the digestate could be avoided by including algae-bacteria processes. The biomass production cost was as low as 1.9 €·kg−1, while the cost for nitrogen removal was 4.3 €·kg N−1.

Piggery Wastewater Treatment with Algae-Bacteria Consortia: Pilot-Scale Validation and Techno-Economic Evaluation at Farm Level

Piggery Wastewater Treatment with Algae-Bacteria Consortia: Pilot-Scale Validation and Techno-Economic Evaluation at Farm Level

Characterization of Variovorax Strain C6d Isolated from the Algae-bacteria Consortia

The rhizosphere microorganisms can form beneficial, pathogenic, or neutral relationships. These relationships can promote plant growth and productivity. Among them, a number of Variovorax isolates from the rhizosphere were isolated. Bacteria Variovorax strain C6d (AB552893) was isolated from the non axenic culture of Chlorella spp., C6. The cell was Gram-negative, motile, non-spore-forming, short and rod-shaped (0.5-1.0x1.5-2.0µm). Colonies were in white colour after 7 days on 10-fold diluted Nutrient Broth. The strain was able to tolerate NaCL to 1.0% but not to 4.0% of NaCl. It grew quite well at temperatures ranging from 10°C to 37°C, yet did not show any growth at 4°C and 42°C. The dominant isoprenoid quinone was ubiquinone 8 (Q8). The major fatty acid composition of this strain was summed feature 3, 16:0 and 18:1:w7. The DNA G+C content of strain C6d was 70.4 mol%.

Effects of algal-bacterial ratio on the growth and cadmium accumulation of Chlorella salina-Bacillus subtilis consortia.

Algae-bacteria consortia have been proven effective in the removal of metal pollutants, but the effects of algal-bacterial ratio in the metal accumulation and resistance by this symbiotic system have not been systematically investigated. In this study, we set up consortia with various ratios of Chlorella salina-Bacillus subtilis, determined their growth, Cd accumulation, levels of intracellular glutathione (GSH), extracellular polysaccharide, phosphorus (P) in the culture medium, and functional groups of consortia after Cd treatments (0.1, 0.5, 1 mg L-1 ) for 7 days. With the addition of B. subtilis in the C. salina culture, the dry weight and specific growth rate of the consortia significantly increased compared with C. salina alone, reaching 68.33 mg and 0.382 (mg L-1 ) d-1 respectively at the 1:4 algal-bacterial ratio with 1 mg L-1 Cd treatment. Maximum Cd removal (51.66%) was also observed upon the same Cd exposure and algal-bacterial ratio. Cadmium was mostly taken up into cells at 1 mg L-1 Cd whereas its adsorption dominated the accumulation when Cd was 0.1 and 0.5 mg L-1 . The amounts of extracellular polysaccharides, GSH, and P of the symbiotic system were also increased by the bacterial addition. Besides, Fouriertransform infrared (FTIR) spectroscopy analysis showed that functional groups like N-H, O-H, and P-O-C were involved in the Cd complexation. Taken together, a higher bacterial ratio promoted the Cd accumulation and detoxification by the C. salina-B. subtilis consortia through intra- and extracellular processes.

Development of a kinetic model to describe six types of symbiotic interactions in a formate utilizing microalgae-bacteria cultivation system

This study investigated an algae/formate-utilizing-bacteria system that has been developed for carbon capture. This photomixotrophic consortium consumed formate to support bacterial growth so that the resulting respiration CO2 could be simultaneously used by algae to avoid CO2 gas-lipid mass transfer limitation. To understand biomass growth and population interactions in this unique system, a kinetic model has been developed to describe algae and bacteria multiplication, formate and nitrogen utilizations, CO2 mass transfer, O2 generation and consumption, lighting condition and shading effect. The simulation indicated that this ecosystem could form six types of interactions (mutualism, commensalism, parasitism, neutralism, amensalism, and competition) depending on the light intensity and nutrient availability. The simulation of both batch culture and chemostat, along with parameter sensitivity tests and experimental observations, offered insights into optimal applications of algae-bacteria consortium based photobiorefinery.

Comparative Treatment Efficiency and Fatty Acid Synthesis of Chlorella vulgaris: Immobilization Versus Co-cultivation

Microalgae consists a promising feedstock for biofuel production due to their high growth rates and lipid content. Microalgal wastewater remediation can achieve both organic matters removal and biodiesel production, leading to economic benefits. In this study, immobilized microalgae and algae-bacteria consortia were used to treat synthetic fracturing wastewater. Organic matter removal, biomass production and lipid synthesis by co-culture of Chlorella vulgaris and Bacillus bacteria were investigated in comparison with an algae immobilization system during the process. The chemical oxygen demand removal rate and lipid concentration of the co-culture were both lower than those of the immobilized C. vulgaris, while algal biomass under the two cultivation conditions was similar. The immobilized algae provided higher amount of fatty acids, especially mono-unsaturated fatty acids, than the algae-bacteria consortia. Most of the fuel properties of biodiesel produced in both immobilized and co-cultured C. vulgaris complied with the specifications for standard biodiesel. The comparative results of enzyme activity showed that immobilization can enhance the activity of acetyl-CoA carboxylase, the key enzyme for fatty acids synthesis, leading to the formation of more fatty acids and lipids. Furthermore, immobilization decreased the ADP-glucose pyrophosphorylase activity and inhibited starch formation. Immobilization favors lipid production and removal of organics by C. vulgaris.

Algae-Bacteria Consortia as a Strategy to Enhance H2 Production.

Biological hydrogen production by microalgae is a potential sustainable, renewable and clean source of energy. However, many barriers limiting photohydrogen production in these microorganisms remain unsolved. In order to explore this potential and make biohydrogen industrially affordable, the unicellular microalga Chlamydomonas reinhardtii is used as a model system to solve barriers and identify new approaches that can improve hydrogen production. Recently, Chlamydomonas–bacteria consortia have opened a new window to improve biohydrogen production. In this study, we review the different consortia that have been successfully employed and analyze the factors that could be behind the improved H2 production.

Cultivation of an Algae-Bacteria Consortium in a Mixture of Industrial Wastewater to Obtain Valuable Products for Local Use

Profitability of biofuel production from microalgae is difficult to achieve but co-locating production with wastewater treatment plants is a possible avenue help to reduce costs. A microalgae culturing project was conducted using wastewater from an industrial park to obtain valuable metabolites from the biomass to eventually use them locally. Different growth conditions were tested with a mixture of wastewater as the culture medium and a native microalgae-bacteria consortium isolated locally. The results showed that this consortium grows well in wastewater and that different fatty acids profiles are produced under the different growth conditions. The optimal culture conditions to produce biomass and extracted lipids are in mixotrophic mode under an irradiance of 200 μmol m−2 s−1 with an injection of 1% of CO2. High amounts of other fatty acids were also produced and could potentially be used to make other co-products. In addition to reducing wastewater treatment costs, the manufacture of biosurfactants could bring additional income to the overall microalgae production process.

Assessment of the Dynamics of Microbial Community Associated with Tetraselmis suecica Culture under Different LED Lights Using Next-Generation Sequencing.

Tetraselmis is a green algal genus, some of whose species are important in aquaculture as well as biotechnology. In algal culture, fluorescent lamps, traditional light source for culturing algae, are now being replaced by a cost-effective light-emitting diodes (LEDs). In this study, we investigated the effect of LED light of different wavelengths (white, red, yellow, and blue) on the growth of Tetraselmis suecica and its associated microbial community structures using the next-generation sequencing (NGS). The fastest growth rate of T. suecica was shown in the red light, whereas the slowest was in yellow. The highest OTUs (3426) were identified on day 0, whereas the lowest ones (308) were found on day 15 under red light. The top 100 OTUs associated with day 0 and day 5 cultures of T. suecica under the red and yellow LED were compared. Only 26 OTUs were commonly identified among four samples. The highest numbers of unique OTUs were identified at day 0, indicating the high degree of initial microbial diversity of the T. suecica inoculum. The red light-unique OTUs occupied 34.98%, whereas the yellow-specific OTUs accounted for only 2.2%. This result suggested a higher degree of interaction in T. suecica culture under the red light, where stronger photosynthesis occurs. Apparently, the microbial community associated with T. suecica related to the oxygen produced by algal photosynthesis. This result may expand our knowledge about the algaebacteria consortia, which would be useful for various biotechnological applications including wastewater treatment, bioremediation, and sustainable aquaculture.

Interaction between Chlorella vulgaris and nitrifying-enriched activated sludge in the treatment of wastewater with low C/N ratio

Abstract Wastewater treatment based on algae-bacteria consortia is expected to find use among other biological processes. In this report, the effects of the inoculation ratios of a Chlorella vulgaris and nitrifier-enriched-activated-sludge (NAS) consortium on nutrient removal, carbon capture, and metabolite generation were investigated under autotrophic conditions. The maximum NH4+-N removal (100%) was observed within 7 days in a photo-bioreactor containing 10% C. vulgaris: 90% NAS (w/w); this consortium is referred to as B10. The maximum PO43--P removal (87.5%) was observed in a pure culture of C. vulgaris after 14 days. Due to the fast nitrification achieved using B10, this system showed the highest nitrate accumulation value of 19.73 mg NO3−-N/L at the end of the experiment. The DO concentration in B10 reached 4 mg/L due to the photosynthetic activity of C. vulgaris, providing appropriate conditions for the NAS. Among all the tested consortium ratios, B90 (90%:10% C. vulgaris/NAS, w/w) showed the highest carbon capture (156 mg), while B10 captured only 43.2 mg of carbon. Furthermore, metabolite analysis showed a positive correlation between the proportion of C. vulgaris and the generation of metabolites in the cultures. A trade-off was observed between nutrient removal and carbon capture in C. vulgaris and NAS co-cultures. Overall, our study shows that the aeration system in conventional nitrification processes could be replaced by a cleaner process based on microalgae, resulting in enhanced nutrient removal, increased carbon capture, reduced metabolite generation, and a decrease in excess sludge production.

Performance of Chlorella sorokiniana-activated sludge consortium treating wastewater under light-limited heterotrophic condition

Light limitation often occurs in algae-bacteria consortium. Chlorella sorokiniana is special for heterotrophic growth in the dark, autotrophic or mixotrophic growth in the light. Wastewater treatment by Chlorella sorokiniana-activated sludge consortium under dark heterotrophic conditions (24 h dark, dark period of 12 h/12 h light/dark) was systematically evaluated for the first time. The performance closely depended on sludge/algae ratio with best initial ratio of 1:2 (R2). Compared to activated sludge (R0), R2 showed enhanced NH4+-N and P removal (by 6% and 10%, respectively), similar COD removal, and better settleability. Notably, less O2 consumption of R2 than activated sludge made energy-saving possible. Further analysis found that interaction made sludge/algae ratio reversal to be 3:1. The promoting interaction between algae and bacteria was associated with up-regulated cofactors and vitamins, while defensive interaction came from secondary metabolites of terpenoids and polyketides. Despite oxidative stress in the dark consortium, photosynthesis of algae reactivated when switched into light. The performance order was light consortium > dark consortium > activated sludge. Nitrosomonas and Dechloromonas were enriched for nutrients removal. The results reveal the superiority of algae-bacteria consortium over activated sludge whether with or without light.