Removal of phosphorus from oyster farm mud sediment using a photosynthetic bacterium, Rhodobacter sphaeroides IL106

A microcosm study of microbial community profiles during sediment remediation using pyrolyzed oyster shells

The accumulation of organic and inorganic components in sediments leads to a deterioration in the environment and an imbalance in the coastal ecosystem. Currently, capping is the most effective technology for remediating polluted sediment and restoring ecosystems. A microcosm experiment was designed using pyrolyzed oyster shell (POS). These were mixed in with coastal sediment or added as a capping layer. The results showed that POS effectively decreased pollutants, including PO₄-P and NH₄-N. Metagenomics analysis was performed using 16S rRNA gene sequencing and the most abundant phyla identified in the POS treated and untreated sediments were Proteobacteria, followed by Firmicutes, Bacteroidetes, Chloroflexi, Fusobacteria, Nitrospirae, and Spirochaetes. The relative abundance of Proteobacteria members of the Class Gammaproteobacteria significantly increased, but Deltaproteobacteria gradually decreased throughout the experiment in POS-covered sediment. This suggests that the POS effectively promoted a shift from anaerobic to facultative anaerobic or aerobic microbial communities in the sediment. Dominant species of facultative anaerobic or microaerophilic bacteria from the order Chromatiales and phylum Nitrospirae were observed in the POS-covered sediment. Based on these study results, it can be concluded that POS is an effective covering material for sediment remediation and restores the microbial communities in sediments.

Improving microbial bioremediation efficiency of intensive aquacultural wastewater based on bacterial pollutant metabolism kinetics analysis

How to effectively bioremediate aquacultural wastewater using microbes is an urgent issue for the application of aquaculture beneficial microorganisms. Purple non-sulfur bacteria (PNSB) are beneficial in preventing related pollution in aquaculture applications. An autochthonous PNSB Rhodobacter sphaeroides was employed in this study to explore an effective bioremediation strategy of aquacultural wastewater. The test bacterium showed high performance in the removal of ammonium (97.50% ± 0.78% of 42 mg L^-1 NH₄⁺-N) and phosphate (93.24% ± 0.71% of 50 mg L^-1 PO₄^3--P) in the synthetic wastewater, which are the two crucial indicators of the aquacultural wastewater bioremediation. The study also unveiled that the imbalanced ratio of nutrients in water was the principal reason for limiting the efficient bioremediation of shrimp-culture wastewater. Therefore, an effective microbial bioremediation strategy was proposed by comprehensively considering bacterial pollutant metabolism kinetics constants such as specific consumption yields of chemical oxygen demand (COD)/phosphorous and nitrogen/phosphorous. Finally, COD, total nitrogen (TN), total phosphorus (TP), and ammonium (NH₄⁺-N) in the wastewater were examined, and the results showed that they all decreased to the acceptable values. In conclusion, this study suggested a novel method for improved bioremediation efficiency of aquacultural wastewater, and the findings revealed that this strategy is promising due to its characteristics to be used in various aquaculture wastewater types.

Enhancement of COD, ammonia, phosphate and sulfide simultaneous removal by the anaerobic photosynthetic bacterium of Ectothiorhodospira magna in batch and sequencing batch culture

An anaerobic photosynthetic bacterium, with chemical oxygen demand (COD), ammonia nitrogen (NH₃-N), total phosphorus (TP) and sulfide (S^2-) simultaneous removal ability, strain SU6, was isolated and identified as belonging to Ectothiorhodospira magna. Its removal efficiencies were simultaneously evaluated in batch culture and influenced in sequencing batch culture. The maximum COD, NH₃-N, TP and S^2- removal rates of 93.04%, 86.70%, 37.55% and 99.99% were obtained in batch culture with an initial pH 8.0 at 35 °C after 72 h. The simultaneous removal efficiency was enhanced in sequencing batch culture, and 789.27 mg/L COD, 68.91 mg/L NH₃-N, 70.20 mg/L S^2- and 5.26 mg/L TP were removed by the end of the last cycle within 24 h. This was the first time of reporting contaminants' simultaneous removal by a pure-cultured photosynthetic bacterium. The experimental results demonstrate that E. magna can efficiently serve as a good candidate in anaerobic wastewater contaminants' simultaneous removal, and maybe as another model anaerobic photosynthetic microorganism for water purification investigations.

White and infrared light continuous photobioreactors for resource recovery from poultry processing wastewater - A comparison

Concentrated wastewaters from agricultural industries represent a key opportunity for the upcycling of organics, nitrogen and phosphorus to higher value products such as microbial protein. Phototrophic or photosynthetic microbes very effectively capture input organics and nutrients as microbial protein. This study compares purple phototrophic bacteria (PPB) and microalgae (photosynthesis) for this purpose, treating real, high strength poultry processing wastewater in continuous photo bioreactors utilising infrared (IR) and white light (WL) respectively. Both reactors could effectively treat the wastewaters, and at similar loading rates (4 kgCOD m^-3d^-1). The infrared reactor (IRR) was irradiated at 18 W m^-2 and the white light reactor (WLR) reactor at 1.5-2 times this. The IRR could remove up to 90% total chemical oxygen demand (TCOD), 90% total nitrogen (TN) and 45% total phosphorus (TP) at 1.0 d hydraulic retention time (HRT) and recover around 190 kg of crude protein per tonne of influent COD at 7.0 kWh per dry tonne^-1 light input, with PPB dominating all samples. In comparison, the WLR removed up to 98% COD, 94% TN and 44% TP at 43-90% higher irradiance compared to the PPB reactor. Microalgae did not dominate the WLR and the community was instead a mix of microbes (algae, bacteria, zooplankton and detritus - ALBAZOD) with a production of approximately 140 kg crude protein per tonne influent COD.

Nitrogen and phosphorus treatment of marine wastewater by a laboratory-scale sequencing batch reactor with eco-friendly marine high-efficiency sediment

We screened and identified a NH₃-N-removing bacterial strain, Bacillus sp. KGN1, and a [Formula: see text] removing strain, Vibrio sp. KGP1, from 960 indigenous marine isolates from seawater and marine sediment from Tongyeong, South Korea. We developed eco-friendly high-efficiency marine sludge (eco-HEMS), and inoculated these marine bacterial strains into the marine sediment. A laboratory-scale sequencing batch reactor (SBR) system using the eco-HEMS for marine wastewater from land-based fish farms improved the treatment performance as indicated by 88.2% removal efficiency (RE) of total nitrogen (initial: 5.6 mg/L) and 90.6% RE of total phosphorus (initial: 1.2 mg/L) under the optimal operation conditions (food and microorganism (F/M) ratio, 0.35 g SCOD_Cr/g mixed liquor volatile suspended solids (MLVSS)·d; dissolved oxygen (DO) 1.0 ± 0.2 mg/L; hydraulic retention time (HRT), 6.6 h; solids retention time (SRT), 12 d). The following kinetic parameters were obtained: cell yield (Y), 0.29 g MLVSS/g SCOD_Cr; specific growth rate (µ), 0.06 d^-1; specific nitrification rate (SNR), 0.49 mg NH₃-N/g MLVSS·h; specific denitrification rate (SDNR), 0.005 mg [Formula: see text]/g MLVSS·h; specific phosphorus uptake rate (SPUR), 0.12 mg [Formula: see text]/g MLVSS·h. The nitrogen- and phosphorus-removing bacterial strains comprised 18.4% of distribution rate in the microbial community of eco-HEMS under the optimal operation conditions. Therefore, eco-HEMS effectively removed nitrogen and phosphorus from highly saline marine wastewater from land-based fish farms with improving SNR, SDNR, and SPUR values in more diverse microbial communities.

ABBREVIATIONS

DO: dissolved oxygen; Eco-HEMS: eco-friendly high efficiency marine sludge; F/M: food and microorganism ratio; HRT: hydraulic retention time; ML(V)SS: mixed liquor (volatile) suspended solids; NCBI: National Center for Biotechnology Information; ND: not determined; qPCR: quantitative real-time polymerase chain reaction; RE: removal efficiency; SBR: sequencing batch reactor; SD: standard deviation; SDNR: specific denitrification rate; SNR: specific nitrification rate; SPUR: specific phosphate uptake rate; SRT: solids retention time; T-N: total nitrogen; T-P: total phosphorus; (V)SS: (volatile) suspended solids; w.w.: wet weight.

Bioremediation of cadmium- and zinc-contaminated soil using Rhodobacter sphaeroides

Bioremediation using microorganisms is a promising technique to remediate soil contaminated with heavy metals. In this study, Rhodobacter sphaeroides was used to bioremediate soils contaminated with cadmium (Cd) and zinc (Zn). The study found that the treatment reduced the overall bioavailable fractions (e.g., exchangeable and carbonate bound phases) of Cd and Zn. More stable fractions (e.g., Fe-Mn oxide, organic bound, and residual phases (only for Zn)) increased after bioremediation. A wheat seedling experiment revealed that the phytoavailability of Cd was reduced after bioremediation using R. sphaeroides. After bioremediation, the exchangeable phases of Cd and Zn in soil were reduced by as much as 30.7% and 100.0%, respectively; the Cd levels in wheat leaf and root were reduced by as much as 62.3% and 47.2%, respectively. However, when the soils were contaminated with very high levels of Cd and Zn (Cd 54.97-65.33 mg kg^-1; Zn 813.4-964.8 mg kg^-1), bioremediation effects were not clear. The study also found that R. sphaeroides bioremediation in soil can enhance the Zn/Cd ratio in the harvested wheat leaf and root overall. This indicates potentially favorable application in agronomic practice and biofortification. Although remediation efficiency in highly contaminated soil was not significant, R. sphaeroides may be potentially and practically applied to the bioremediation of soils co-contaminated by Cd and Zn.

Chromium removal from solution by five photosynthetic bacteria isolates

Biological method has been recognized as a low-cost and ecofriendly approach for removing heavy metals from aqueous wastes. In this study, the ability of five photosynthetic bacteria isolates (strains labeled SC01, HN02, SC05, JS01, and YN01) was examined for their ability to remove Cr from Cr-containing solutions. Furthermore, the possible removal mechanisms were elucidated by comparing chromium removal rates, antioxidant reaction, and accumulation of reactive oxygen species (ROS). Among the five bacteria, strains SC01 and SC05 presented the highest removal rates of chromium ions and the activity of cysteine desulfhydrase under Cr stress. They also showed lower levels of ROS and cell death than the other three bacteria strains under Cr stress. In addition, total bacteriochlorophyll content and activities of six antioxidant enzymes in SC01 were highest among these selected strains. On the contrary, strain HN02 presented the lowest level of Cr removal and the lowest activities of antioxidant enzymes. It also exhibited the highest level of ROS under Cr(VI) stress. Overall, these results show that the strains SC01 and SC05 have good Cr removal ability and could be used for removal of Cr in industrial effluents.

Bioremediation of lead contaminated soil with Rhodobacter sphaeroides

Bioremediation with microorganisms is a promising technique for heavy metal contaminated soil. Rhodobacter sphaeroides was previously isolated from oil field injection water and used for bioremediation of lead (Pb) contaminated soil in the present study. Based on the investigation of the optimum culturing conditions and the tolerance to Pb, we employed the microorganism for the remediation of Pb contaminated soil simulated at different contamination levels. It was found that the optimum temperature, pH, and inoculum size for R. sphaeroides is 30-35 °C, 7, and 2 × 10(8) mL(-1), respectively. Rhodobacter sphaeroides did not remove the Pb from soil but did change its speciation. During the bioremediation process, more available fractions were transformed to less accessible and inert fractions; in particular, the exchangeable phase was dramatically decreased while the residual phase was substantially increased. A wheat seedling growing experiment showed that Pb phytoavailability was reduced in amended soils. Results inferred that the main mechanism by which R. sphaeroides treats Pb contaminated soil is the precipitation formation of inert compounds, including lead sulfate and lead sulfide. Although the Pb bioremediation efficiency on wheat was not very high (14.78% root and 24.01% in leaf), R. sphaeroides remains a promising alternative for Pb remediation in contaminated soil.

Characterization of Rhodopseudomonas palustris strain 2C as a potential probiotic

Photosynthetic bacteria (PSB) are prokaryotes that first appeared on the earth 2 billion years ago. Being rich in nutrients and having unique biological transformational function, PSB have been used as medicinal ingredients and healthcare products. However, there is insufficient information about the probiotic properties of PSB. The aim of this study was to characterize the potential probiotic properties of Rhodopseudomonas palustris strain 2C. The tolerance of strain 2C to low pH, high bile salt and simulated gastrointestinal conditions was determined. The susceptibility of strain 2C to 11 antibiotics was screened. The in vitro antioxidative activity and acute toxicity of strain 2C were performed. The survival duration of strain 2C after it had been repeatedly ingested by Wistar rats was determined. Strain 2C was tolerant to low pH, high bile salt concentration, and simulated gastrointestinal conditions. Strain 2C was only resistant to two of the 11 tested antibiotics (penicillin and ampicillin), and it showed antioxidative activity in vitro. When ingested by rats, strain 2C did not cause any bacteria translocation or tissue damage. The survival duration of strain 2C depending on doses ingested by the rats, 3 days after the termination of intake, it could no longer be enriched from the feces. Taken together, these findings indicate that strain 2C may be a potential probiotic strain.

Coenzyme Q10 production in a 150-l reactor by a mutant strain of Rhodobacter sphaeroides

For the commercial production of CoQ(10), batch-type fermentations were attempted in a 150-l fermenter using a mutant strain of R. sphaeroides. Optimum temperature and initial aeration rate were found to be 30 degrees C and 2 vvm, respectively. Under optimum fermentation conditions, the maximum value of specific CoQ(10) content was achieved reproducibly as 6.34 mg/g DCW after 24 h, with 3.02 g/l of DCW. During the fermentation, aeration shift (from the adequate aeration at the early growth phase to the limited aeration in active cellular metabolism) was a key factor in CoQ(10) production for scale-up. A higher value of the specific CoQ(10) content (8.12 mg/g DCW) was achieved in fed-batch fermentation and comparable to those produced by the pilot-scale fed-batch fermentations of A. tumefaciens, which indicated that the mutant strain of R. sphaeroides used in this study was a potential high CoQ(10) producer. This is the first detailed study to demonstrate a pilot-scale production of CoQ(10) using a mutant strain of R. sphaeroides.

Phototrophic growth of Rubrivivax gelatinosus in poultry slaughterhouse wastewater

Rubrivivax gelatinosus was grown in Pfennig's synthetic medium (PM) and in treated wastewater from poultry slaughterhouse (TW) to assess growth profiles for biomass production. Cultures inoculated at 1% (v/v) were grown under anaerobiosis at 30+/-2 degrees C and 1400+/-200 lux for 12 days. Regular absorbance curves for R. gelatinosus were found both on PM and TW. On PM, the highest dry weight of biomass, 0.39 gL(-1), was achieved in the 216-h culture and the highest specific growth rate of 0.2960 h(-1) occurred in the 24-h culture. On TW, the highest biomass of 0.57 gL(-1) was also obtained in the 216-h culture and the highest specific growth rate, 0.1970 h(-1), was achieved in the 48-h culture. For productivity and chemical oxygen demand investigations, the cultivation was accomplished in the TW under anaerobiosis at 32+/-2 degrees C and 4000+/-500 lux, for 10 days. Productivity was 0.085 g biomass (d.w.) L(-1) day(-1), with a COD decrease of 91%.

Biosorption and Bioreduction of Trivalent Aurum by Photosynthetic Bacteria Rhodobacter capsulatus

Biosorption has been shown to be an eco-friendly approach to remove heavy metal ions. In this study, the photosynthetic bacteria Rhodobacter capsulatus was screened and found to have strong ability to adsorb Au(III). The maximum specific uptake of living cells was over 92.43 mg HAuCl(4)/g dry weight of cell in the logarithmic phase. Biosorpion ability would be enhanced by an acidic environment. As the main cations, during biosorption the quantity of Mg(2+) exchanged was more than Na(+). Biosorbed Au(III) could be reduced by carotenoid and enzymes embedded and/or excreted by R. capsulatus, which might be the mechanism of photosynthtic bacteria metal tolerance.

Recent development of anaerobic digestion processes for energy recovery from wastes

Anaerobic digestion leads to the overall gasification of organic wastewaters and wastes, and produces methane and carbon dioxide; this gasification contributes to reducing organic matter and recovering energy from organic carbons. Here, we propose three new processes and demonstrate the effectiveness of each process. By using complete anaerobic organic matter removal process (CARP), in which diluted wastewaters such as sewage and effluent from a methane fermentation digester were treated under anaerobic condition for post-treatment, the chemical oxygen demand (COD) in wastewater was decreased to less than 20 ppm. The dry ammonia-methane two-stage fermentation process (Am-Met process) is useful for the anaerobic treatment of nitrogen-rich wastes such as waste excess sludge, cow feces, chicken feces, and food waste without the dilution of the ammonia produced by water or carbon-rich wastes. The hydrogen-methane two-stage fermentation (Hy-Met process), in which the hydrogen produced in the first stage is used for a fuel cell system to generate electricity and the methane produced in the second stage is used to generate heat energy to heat the two reactors and satisfy heat requirements, is useful for the treatment of sugar-rich wastewaters, bread wastes, and biodiesel wastewaters.

Optimization of biological phosphorus removal from contaminated sediments with phosphate-solubilizing microorganisms

This study focused on the characteristics of phosphate-solubilizing microorganisms (PSMs) which can be applied for the removal of phosphorus from sediments to prevent eutrophication of lakes or ponds. A PSM isolated from rhizospheric soil and temporarily identified as Burkholderia glathei (MB 14) produced gluconate and acetate using glucose as a carbon source and its metabolic activity caused the pH of the liquid medium to decrease as low as 4.4. The molar ratio of solubilized PO4(3-)-P to total organic acids, gluconate and acetate, in the liquid medium was 1:2, which was lower than the theoretical molar ratio of 1:3 using Ca3(PO4)2 as a model phosphorus compound. In addition, biological PO4(3-)-P solubilization with MB 14 was more efficient than the direct addition of equivalent acid to the liquid medium. These results indirectly suggest that organic acids chelate Ca2+ during solubilization of PO4(3-)-P. The growth conditions for MB 14 that produced the maximum PO4(3-)-P solubilization were carbon sources of 8 g/l of glucose and 2 g/l of sucrose, and 0.1 g/l of arginine as a nitrogen source under an anoxic environment. The PSM species, MB 14, grown under these conditions was applied to treat contaminated dredged sediments in a bioslurry reactor. In 9 d, MB 14 solubilized 34.5% of total phosphorus in the contaminated dredged sediments.

Biosorption of cadmium ions using a photosynthetic bacterium, Rhodobacter sphaeroides S and a marine photosynthetic bacterium, Rhodovulum sp. and their biosorption kinetics

We examined the biosorption characteristics of cadmium ions onto a photosynthetic bacterium, Rhodobacter sphaeroides S and a marine photosynthetic bacterium Rhodovulum sp. PS88 in a batch culture system. Both photosynthetic bacteria are capable of cadmium removal with 30 g/l sodium chloride and divalent cations (Mg2+ and Ca2+) in the culture medium. In particular, the strain PS88 shows a high removal ratio and high specific removal rate of cadmium ions from the culture medium under aerobic-dark (heterotrophic) and anaerobic-light (photoheterotrophic) conditions. The adsorption of cadmium onto strains PS88 and S is dependent on the cadmium concentration, and follows the Freundlich adsorption isotherm. In addition, biosorption isotherms for cadmium show that the strain PS88 exhibits higher values of the empirical constant for the cadmium adsorption capacity, Kr, than that of the strain S under both aerobic-dark (K(f)=17.44) and anaerobic-light (K(f)=1.270) conditions.

Applications of photosynthetic bacteria for medical fields

The medical applications of photosynthetic bacteria are summarized. Photosynthetic bacteria can produce various types of physiological active substance such as vitamin B(12), ubiquinone (coenzyme Q10), 5-aminolevulinic acid (ALA), porphyrins and RNA. In particular, photosynthetic bacterial ALA was commercially applied to cancer diagnosis and treatment. Recently, ALA has been applied to the treatment of acne vulgaris and the suppression of the inflammatory response to coronary and iliac injuries. In addition, the recent applications of RNA from a marine photosynthetic bacterium as a medical supplement for immune improvement and suppression of infection are described. Furthermore, the feasible application of a biopolymer consisting of RNA from a photosynthetic bacterium as a drug delivery system (DDS) to cancer treatment is described.

Effect of pH change on the performance and microbial community of enhanced biological phosphate removal process

An acetate-rich wastewater, containing 170 mg/L of total organic carbon (TOC), 13 mg/L of N, and 15 mg/L of P, was treated using the enhanced biological phosphate removal (EBPR) process operated in a sequencing batch reactor. A slight change of pH of the mixed liquor from 7.0 to 6.5 led to a complete loss of phosphate-removing capability and a drastic change of microbial populations. The process steadily removed 94% of TOC and 99.9% of P from the wastewater at pH 7.0, but only 93% TOC and 17% of P 14 days after the pH was lowered to pH 6.5. The sludge contained 8.8% P at pH 7.0, but only 1.9% at pH 6.5. Based on 16S rDNA analysis, 64.8% of the clones obtained from the sludge at pH 7.0 were absent in the pH 6.5 sludge. The missing microbes, some of which were likely responsible for the phosphate removal at pH 7.0, included beta-Proteobacteria, Actinobacteria, Bacteriodetes/Chlorobi group, plus photosynthetic bacteria and Defluvicoccus of the alpha-Proteobacteria. Among them, the last two groups, which represented 9.3% and 10.1% of the EBPR sludge at pH 7.0, have rarely been reported in an EBPR system.