Search

[Display omitted] • Pumice and smectite are robust carriers for cell immobilization recycling. • Bacteria-pumice and bacteria-smectite nanocomposites are efficient for recycling. • Continuous production of microbial products from wastes was achieved. • Secondary treatment is unneeded in treating waste using the proposed nanocomposites. Recycling waste into commercial products is a profitable strategy but the lifetime of immobilized cells for long-term waste treatment remains a problem. This study presents alternative cell immobilization methods for valorizing food waste (FW) and oily food waste (OFW) to microbial carotenoids and proteins. Carriers (pumice or smectite), magnetite nanoparticles, and isolated photosynthetic bacteria were integrated to obtain magnetically recoverable bacteria-pumice and bacteria-smectite nanocomposites. After recycling five batches (50 d), chemical oxygen demand removal from FW reached 76% and 78% with the bacteria-pumice and bacteria-smectite nanocomposite treatments, respectively, and oil degradation in OFW reached 71% and 62%, respectively. Destructive changes did not occur, suggesting the durability of nanocomposites. The used nanocomposites had no impact on the lifespan of Moina macrocopa or water quality as assessed by toxicity analysis. Bacteria-pumice and bacteria-smectite nanocomposites are efficient for food waste recycling and do not require secondary treatment before being discharged into the environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Efficient N and P removal was realized by the microalgae-assisted HNAD system. • The biological removal process contributed 55.3–71.8 % of nitrogen removal. • BIPP undertook approximately 45.6–51.8% of phosphorus removal. • Microalgae might induce the development of photosynthetic bacteria in biofilm. • The microalgae-assisted HNAD system was energy self-sustaining. A microalgae-assisted heterotrophic nitrification-aerobic denitrification (HNAD) system for efficient nutrient removal from high-salinity wastewater was constructed for the first time as a cost-effective process in the present study. Excellent nutrient removal (∼100.0 %) was achieved through the symbiotic system. The biological removal process, biologically induced phosphate precipitation (BIPP), microalgae uptake, and ammonia stripping worked together for nutrient removal. Furthermore, the biological removal process achieved by biofilm contributed to approximately 55.3–71.8 % of nitrogen removal. BIPP undertook approximately 45.6–51.8 % of phosphorus removal. Batch activity tests confirmed that HNAD fulfilled an extremely critical role in nitrogen removal. Microalgal metabolism drove BIPP to achieve efficient phosphorus removal. Moreover, as the main HNAD bacteria, OLB13 and Thauera were enriched. The preliminary energy flow analysis demonstrated that the symbiotic system could achieve energy neutrality, theoretically. The findings provide novel insights into strategies of low-carbon and efficient nutrient removal from high-salinity wastewater. [ABSTRACT FROM AUTHOR]

[Display omitted] • New mechanistic model for purple phototrophic bacteria (PPB) is developed. • A novel empirical constant is introduced for parallel metabolic growth. • Most impactful parameters are identified by sensitivity analysis. • Kinetic parameters are calibrated through dedicated experiments. • Likely-to-occur perturbations are simulated to assess process performance. Purple phototrophic bacteria (PPB) show an underexplored potential for resource recovery from wastewater. Raceway reactors offer a more affordable full-scale solution on wastewater and enable useful additional aerobic processes. Current mathematical models of PPB systems provide useful mechanistic insights, but do not represent the full metabolic versatility of PPB and thus require further advancement to simulate the process for technology development and control. In this study, a new modelling approach for PPB that integrates the photoheterotrophic, and both anaerobic and aerobic chemoheterotrophic metabolic pathways through an empirical parallel metabolic growth constant was proposed. It aimed the modelling of microbial selection dynamics in competition with aerobic and anaerobic microbial community under different operational scenarios. A sensitivity analysis was carried out to identify the most influential parameters within the model and calibrate them based on experimental data. Process perturbation scenarios were simulated, which showed a good performance of the model. [ABSTRACT FROM AUTHOR]

[Display omitted] • Microalgal-bacterial granules sludge formation can be accelerated by light condition. • MBGS exhibited 10% greater TIN removal under high light, surpassing other groups. • Salinity stress enriched salt-tolerant and functional bacteria in the reactor. • Light and salinity jointly hinder NOB activity. Photosynthetic microorganisms in microalgal-bacterial granular sludge offer advantages in wastewater treatment processes. This study examined the effects of light intensity and salinity on microalgal-bacterial granular sludge formation and microbial changes. Activated sludge was inoculated into three bioreactors and operated in batch treatment mode for 100 days under different light intensities (0, 60, and 120 μmol m−2 s−1) and staged increases in salinity concentration (0, 1, 2, and 3%). Results showed that microalgal-bacterial granular sludge was successfully formed within 30 days, and high light exposure increased algal particle stability and inorganic nitrogen removal (63, 66, 71%), while chemical oxygen demand removal (>95%) was similar across groups. High-throughput sequencing results showed that the critical algae were Chlorella and diatoms, while the main bacteria included Paracoccus and Xanthomarina with high extracellular polymeric substance production. This study aims to enhance the comprehension of MBGS processes in saline wastewater treatment under varying light intensities. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Piggery wastewater load governed wastewater treatment and biomethane quality. • A CH 4 concentration of 90.8% was achieved with 4 times diluted piggery wastewater. • Volatile fatty acids promoted CO 2 capture in Calvin cycle and thus biogas upgrading. • Purple phototrophic bacteria supported higher biogas quality than microalgae. Abstract The potential of purple phototrophic bacteria (PPB) for the simultaneous treatment of piggery wastewater (PWW) and biogas upgrading was evaluated batchwise in gas-tight photobioreactors. PWW dilution was identified as a key parameter determining the efficiency of wastewater treatment and biomethane quality in PPB photobioreactors. Four times diluted PWW supported the most efficient total organic carbon (TOC) and total nitrogen removals (78% and 13%, respectively), with CH 4 concentrations of 90.8%. The influence of phosphorous concentration (supplementation of 50 mg L−1 of P-PO 4 3−) on PPB-based PWW treatment coupled to biogas upgrading was investigated. TOC removals of ≈60% and CH 4 concentrations of ≈90.0% were obtained regardless of phosphorus supplementation. Finally, the use of PPB and algal-bacterial consortia supported CH 4 concentrations in the upgraded biogas of 93.3% and 73.6%, respectively, which confirmed the potential PPB for biogas upgrading coupled to PWW treatment. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • PSB wastewater treatment and resource recovery technology was reviewed. • PSBs classification, metabolism, and the market application were described. • The feasibility, procedures, bioreactors of this technology were summarized. • Feasibility and potential of PSB non-toxic wastewater treatment was evaluated. • Issues that concern the industrialization at the plant scale were listed. Abstract Generating or recycling water and resources from wastewater other than just treating wastewater is one of the most popular trends worldwide. Photosynthetic bacteria (PSB) wastewater treatment and resource recovery technology is one of the most potential methods. PSBs are non-toxic and contain lots of value-added products that can be utilized in the agricultural and food industries. They are effective to degrade pollutants and synthesize useful biomass, thus realizing wastewater treatment, bioresource production, and eliminating waste sludge. If all the nutrients in wastewaters could be bio-converted by PSB, then pollutant reductions and economic benefits would be achieved. This review paper firstly describes and summarizes this technology, including PSBs classification, metabolism, and the market application. The feasibility, technical procedures, bioreactors, pollutant removal, and bioresource production are also summarized, compared and evaluated. Issues that concern the advantages and industrialization of this technologies at the plant scale are also discussed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Photosynthetic bacteria and microalgae provided similar wastewater treatment. • Phototrophic bacteria exhibited higher organic carbon removal than microalgae. • HRT governed pollutant removal and biomass productivity in both photobioreactors. • Microalgae and bacteria population structure were determined by HRT. Abstract This study evaluated the performance of two open-photobioreactors operated with microalgae-bacteria (PBR-AB) and purple photosynthetic bacteria (PBR-PPB) consortia during the treatment of diluted (5%) piggery wastewater (PWW) at multiple hydraulic retention times (HRT). At a HRT of 10.6 days, PBR-AB provided the highest removal efficiencies of nitrogen, phosphorus and zinc (87 ± 2, 91 ± 3 and 98 ± 1%), while the highest organic carbon removals were achieved in PBR-PPB (87 ± 4%). The decrease in HRT from 10.6, to 7.6 and 4.1 day caused a gradual deterioration in organic carbon and nitrogen removal, but did not influence the removal of phosphorus and Zn in both photobioreactors. The decrease in HRT caused a severe wash-out of microalgae in PBR-AB and played a key role in the structure of bacterial population in both photobioreactors. In addition, batch biodegradation tests at multiple PWW dilutions (5, 10 and 15%) confirmed the slightly better performance of algal-bacterial systems regardless of PWW dilution. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The first report of effects of light-dark cycles on PSB wastewater treatment. • Varying light-dark cycles achieved higher substances yields at given energy. • 24 h light/24 h dark cycle led the best biomass production and NH 3 -N removal. • 3 h light/3h dark cycle led the highest protein and coenzyme Q 10 production. Abstract Photosynthetic bacteria (PSB) wastewater treatment is a novel method with great potential for resource recovery. Light-dark cycle is important for photosynthetic microorganisms, but its impact on PSB wastewater treatment is still unclear. This study evaluated the effects of four light-dark cycles on PSB biomass, valuable substances production, and pollutant removal. Results indicate that the highest biomass concentration was obtained under 24 h light/24 h dark cycle. The highest concentrations of protein and coenzyme Q 10 were obtained under 3 h light/3h dark cycle (826.73 and 88.8 mg/g, respectively). Pigment production were stable under all light-dark cycles tested. Light-dark cycles had little effect on COD and TP removal, while 24 h light/24 h dark cycle resulted in the highest NH 3 -N removal. ATP and RuBisCO concentrations followed similar trends under different light-dark cycles. These results revealed that PSB could provide more biomass and valuable substances with given energy by changing light-dark cycles. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • This paper reports for the first time the light-aerobic condition for PSB-MBR. • The best performances were achieved under light-aerobic condition. • The highest abundance of Proteobacteria was obtained under light-aerobic condition. • The microbial diversity was lower when light and oxygen co-existed. Abstract The combined photosynthetic bacteria (PSB) and membrane bioreactor (MBR) technology has the great advantage of simultaneously realizing wastewater purification and bio-resource recovery and has attracted increasing attention in recent years. Light-oxygen conditions are the most vital factor in wastewater treatment. The special light-aerobic condition was first applied to PSB-MBR wastewater treatment, and it was compared with three typical light-oxygen conditions. The results showed that the highest chemical oxygen demand (COD) removal efficiency (96.28%) and the highest biomass production (1.12 g/L/d) were simultaneously obtained under light-aerobic condition. This phenomenon overcame the limitations whereby optimal pollutant removal and bio-resource recovery could not be achieved at the same time. An analysis of the microbial community showed that different light-oxygen conditions caused large variations in the microbial community composition of PSB-MBR. The microbial diversity was lower when light and oxygen co-existed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Urea and Nitrite tested (vs nitrate) between 8.5 and 120 mM on Arthrospira sp. PCC 8005. • Modified cultivation approach avoids inhibitory effects of urea. • Evaluation performed under batch and continuous feeding. • Modified biochemical and proteomic profile exhibited by urea fed cultures. • Higher protein and pigment content quantified in urea fed cells. Abstract This study was conducted with the aim of embedding circular economies (waste recycling) with photosynthetic biorefineries, for production of commercially viable by-products. Since nitrogen source constitute the major input costs for commercial Arthrospira sp. production, the use of nitrogen rich wastewater for Arthrospira sp. cultivation could significantly reduce their production costs. This study evaluated the effects of high concentrations (8.5–120 mM) of alternative nitrogen sources (urea, ammonium and nitrite) on the biochemical, pigment and proteomic profile of Arthrospira sp., under batch and continuous conditions. Arthrospira sp. cells fed with urea were quantified with modified biochemical and proteomic profile compared to the nitrate fed cells. No inhibitory effect of urea was observed on the biomass even at 120 mM. Nitrite fed cells exhibited comparable biochemical and proteomic profiles as nitrate fed cells. These results clearly indicated at the possibility of using urea rich wastewater streams for profitable cultivation of Arthrospira sp. [ABSTRACT FROM AUTHOR]

Anoxygenic phototrophic bacteria (APB) pay a key role in biogeochemical cycles, and it can convert light energy to chemical energy by photosynthesis process. Photosynthetic microbial fuel cell (photo-MFC) is regarded as a promising energy-harvesting technology, which is also applied to environment treatment in recent years. The previous studies show that photo-MFC with APB have higher power putout than other bioelectrochemical systems. However, photo-MFC with APB is not reviewed due to some limited factors in the development process. In this review, photo-MFC with APB is treated according to its electron transfer pathways, the current understanding, APB strains, application, influence of substrates, and economic assessment. Meanwhile, knowledge of photosynthesis components and electron transfer pathways of APB is crucial for developing new energy and easing the serious energy crisis. Moreover, some new insights (the optimization of light source and self-sustaining bioelectricity generation) are proposed for the future explorations. [ABSTRACT FROM AUTHOR]

Resource recovery, preferably as high value products, is becoming an integral part of modern wastewater treatment, with conversion to heterotrophic or phototrophic/photosynthetic microbes a key option to minimise dissipation, and maximise recovery. This study compares the treatment capacities of purple phototrophic bacteria (PPB) and microalgae of five agri-industrial wastewaters (pork, poultry, red meat, dairy and sugar) to recover carbon, nitrogen, and phosphorous as a microbial product. The mediators have different advantages, with PPB offering moderate removals (up to 74% COD, 80% NH 4 -N, 55% PO 4 -P) but higher yields (>0.75 gCOD removed gCOD added −1 ) and a more consistent, PPB dominated (>50%) product, with a higher crude protein product (>0.6 gCP gVSS −1 ). The microalgae tests achieved a better removal outcome (up to 91%COD, 91% NH 4 -N, 73%PO 4 -P), but with poorer quality product, and <30% abundance as algae. [ABSTRACT FROM AUTHOR]

Refractory membrane concentrate generated from the membrane bioreactor (MBR) process remains a big challenge. With high pollution loads, high salinity and low biodegradability, membrane concentrates are difficult to be treated by conventional biological treatments. In this work, photosynthetic bacteria (PSB) were employed to handle this problem. The results showed that PSB could simultaneously remove COD, NH 3 -N, NO 3 − -N, salinity and chroma from the membrane concentrate. The removal efficiency of COD, NH 3 -N, NO 3 − -N, salinity and chroma reached 24.0%, 78.0%, 81.6%, 57.0% and 60.0% respectively. Dark-aerobic condition was more beneficial for pollutants removal. The tolerance mechanism of PSB in treating membrane concentrate was then analyzed. The contents of protein and carotenoid in PSB increased by 38.7% and 20.7% due to the defense stress effects. The content of bacteriochlorin decreased by 42.9% while the content of coenzyme Q 10 was stable at 8.4–8.8%. [ABSTRACT FROM AUTHOR]

In order to achieve simple pollutant removal and simultaneous resource recovery in high-COD-non-toxic wastewater treatment, a one-step photosynthetic bacteria (PSB) method was established using batch study experiment. The effluent COD met the national discharge standard, and biomass with rich protein and high-value substances was efficiently produced. It eliminated the demand of post-treatment for conventional PSB treatment. Results showed that Rhodopseudomonas effectively treated brewery wastewater and achieved biomass proliferation. Yeast extract was the best additive for PSB growth and the effluent COD was below 80 mg/L with 400 mg/L yeast extract, meeting the national discharge standard. In addition, the PSB biomass increased by 2.6 times, and the cells were rich in protein, polysaccharide, carotenoids, bacteriochlorophyll and coenzyme Q10, reaching 420.9, 177.6, 2.53, 10.75 and 38.6 mg/g respectively. This work demonstrated the great potential of PSB for high-COD non-toxic wastewater treatment in one-step process. [ABSTRACT FROM AUTHOR]

Effect of substrate concentration on photo-fermentative hydrogen production was studied with a self-designed 4 m 3 pilot-scale baffled photo-fermentative hydrogen production reactor (BPHR). The relationships between parameters, such as hydrogen production rate (HPR, mol H 2 /m 3 /d), hydrogen concentration, pH value, oxidation–reduction potential, biomass concentration (volatile suspended solids, VSS) and reducing sugar concentration, during the photo-fermentative hydrogen production process were investigated. The highest HPR of 202.64 ± 8.83 mol/m 3 /d was achieved in chamber #3 at a substrate concentration of 20 g/L. Hydrogen contents were in the range of 42.19 ± 0.94%–49.71 ± 0.27%. HPR increased when organic loading rate was increased from 3.3 to 20 g/L/d, then decreased when organic loading rate was further increased to 25 g/L/d. A maximum HPR of 148.65 ± 4.19 mol/m 3 /d was obtained when organic loading rate was maintained at 20 g/L/d during continuous bio-hydrogen production. [ABSTRACT FROM AUTHOR]

This work proposed a novel approach to achieve an extremely high protein content in photosynthetic bacteria (PSB) using biogas slurry as a culturing medium. The results showed the protein content of PSB could be enhanced strongly to 90% in the biogas slurry, which was much higher than reported microbial protein contents. The slurry was partially purified at the same time. Dark-aerobic was more beneficial than light-anaerobic condition for protein accumulation. High salinity and high ammonia of the biogas slurry were the main causes for protein enhancement. In addition, the biogas slurry provided a good buffer system for PSB to grow. The biosynthesis mechanism of protein in PSB was explored according to theoretical analysis. During biogas slurry treatment, the activities of glutamate synthase and glutamine synthetase were increased by 26.55%, 46.95% respectively. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) is an important parameter in photosynthetic bacteria (PSB) wastewater treatment. This study set different DO levels and detected the pollutants removal, PSB growth and pigments production. Results showed that DO significantly influenced the performances of PSB wastewater treatment process. The highest COD (93%) and NH 3 -N removal (83%) was achieved under DO of 4–8 mg/L, but DO of 2–4 mg/L was recommended considering the aeration cost. PSB biomass reached 1645 mg/L under DO of 4–8 mg/L with satisfying co-enzyme Q10 content. The biomass yield was relatively stable at all DO levels. For bacteriochlorophyll and carotenoids, DO > 1 mg/L could satisfy their production. On the other hand, DO < 0.5 mg/L led to the highest dehydrogenase activity. According to the different purposes, the optimal treatment time was different. The most pigments production occurred at 24 h; biomass reached peak at 48 h; and the optimal time for pollutants removal was 72 h. [ABSTRACT FROM AUTHOR]

The future wastewater treatment requires high-efficiency and energy-saving technology. Anoxygenic photosynthetic bacteria (APB) is deemed as an eco-friendly microorganism, which could be employed in wastewater treatment. Here, monochromatic near-infrared (MNIR) light emitting diode (LED) was used, and three key factors (light quality, light intensity and photoperiod) of it were analyzed by a response surface methodology (RSM) in APB wastewater treatment. The results showed that light quality was the biggest impact factor in APB wastewater treatment, and nearly 58.07% of NH 4 + -N and 70.62% of chemical oxygen demand (COD) could be removed based on 46.4% of that theoretically possible. The light quality’s study revealed that APB had the highest NH 4 + -N and COD removal, biomass production, and bacteriochlorophyll a production with 850 nm IR LED. Moreover, the application of optimal MNIR LED could not only save energy, but also avoid algae bloom of photo-bioreactors (PBR). [ABSTRACT FROM AUTHOR]

[Display omitted] • Nano-SnO 2 and cell immobilization technology were applied to PFHP process. • Immobilized cells produced more H 2 than free cells. • Nano-SnO 2 addition could promote PFHP performance. • The CHY increased by 18.54% with the addition of nano-SnO 2. • The light conversion efficiency increased by 12.41% with nano-SnO 2 addition. Bacterial immobilization is a common method in anaerobic fermentation, since of the maintenance of high bacterial activity, insurance of high density microbial during continuous fermentation, and quick adaptability to the environment. While, the bio-hydrogen production capacity of immobilized photosynthetic bacteria (I-PSB) is seriously affected by the low light transfer efficiency. Hence, in this study, photo-catalytic nano-particles (PNPs) was added into the photo-fermentative bio-hydrogen production (PFHP) system, and its enhancement effects of bio-hydrogen production performance were investigated. Results showed that the maximum cumulative hydrogen yield (CHY) of I-PSB with 100 mg/L nano-SnO 2 (154.33 ± 7.33 mL) addition was 18.54% and 33.06% higher than those of I-PSB without nano-SnO 2 addition and control group (free cells), and the lag time was the shortest indicating a shorter cell arrest time, more cells and faster response. Maximum energy recovery efficiency and light conversion efficiency were also found to be increased by 18.5% and 12.4%, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • PPB can be efficiently grown as biofilm in outdoor flat plate reactors. • Attached growth did not compromise treatment performance nor productivities. • The product quality in the biofilm was much higher than in the suspended biomass. • Biomass productivities of 16 ± 2.2 gCOD·m−2·d−1 were achieved during attached growth. • The harvested biofilm could be used as feed. Purple phototrophic bacteria (PPB) can produce single-cell protein from wastewater at high yields. Growing in a biofilm vs suspended can improve product quality and consistency. This study compares suspended and attached growths of enriched PPB cultures in an outdoor flat plate photobioreactor treating poultry-processing wastewater. Attached growth had lower VFA removal efficiencies (95 ± 2.7 vs 84 ± 6.4 %) due to light limitations and low substrate diffusion rates. Nevertheless, similar overall treatment performances and productivities were achieved (16 ± 2.2 and 18 ± 2.4 gCOD·m−2·d−1 for attached and suspended) at loading rates of 1.2–1.5 gCOD·L−1·d−1. Biofilms had higher quality than suspended biomass, with lower ash contents (6.9(0.6)% vs 57(16)%) and higher PPB abundances (0.45–0.67 vs 0.30–0.45). The biofilm (20–50 % of the total biomass) might be used as feed and the suspended fraction as fertiliser, improving the economics of the process. Semi-continuous PPB growth outdoors as biofilm is technically feasible, obtaining a superior product without jeopardising performance. [ABSTRACT FROM AUTHOR]

Anaerobic membrane bioreactors have attracted increasing interest in the field of wastewater treatment. However, significant amounts of organic matter, nitrogen and sulphide in the effluent may limit its reuse. A photosynthetic bacteria-based membrane bioreactor is proposed for the further treatment of this effluent. A pilot-scale unit was run outdoor for over 900 h to assess the process performance at short hydraulic retention time. After an initial biomass development, simultaneous removal of soluble organic matter and nitrogen was achieved (65% and 39%, respectively). In addition, a significant concentration of sulphate was detected in the permeate, revealing an evident sulphide oxidation. Despite the accumulation of biopolymer clusters in the biological suspension, membrane fouling was effectively mitigated by air-aided backwashing, allowing a sustainable operation. Several strains of bacteria were identified including the photoheterotrophic bacteria Rhodopseudomonas sp. and the nitrifying and denitrifying bacteria Chryseobacterium sp. [ABSTRACT FROM AUTHOR]

Photosynthetic hydrogen production from organic wastewaters using immobilized mixed culture with photosynthetic bacteria (PSB) was studied. A PSB consortium was immobilized by alginate matrix to form granules. The so-yielded granules exhibited minimal diffusional resistances to substrates and to illumination penetration but still produced more hydrogen from synthetic wastewater than the free cells at identical experimental conditions. Optimal granule size, cell loadings, and cell ages for granules and the minimum substrate concentration and maximum illumination intensity requited to maximize hydrogen production were studied. The applied alginate matrix can provide shield to embedded cells from external challenges, likely the produced proton gradients from the surroundings. [ABSTRACT FROM AUTHOR]

Huge amount of aging biogas slurry is in urgent need to be treated properly. However, due to high NH 3 -N concentration and low C/N ratio, this aging biogas slurry is refractory for traditional methods. Its denitrification has become a big challenge. In this paper, photosynthetic bacteria (PSB) were employed to handle this problem. The results showed denitrification of aging biogas slurry by PSB treatment was promising. The highest removal efficiency of NH 3 -N reached 99.75%, much higher than all other treatments. The removal of NH 3 -N followed pseudo zero order reaction under dark-aerobic condition. The better inoculation rate for NH 3 -N removal was 30%; and aerobic condition was more beneficial for NH 3 -N removal than anaerobic condition because of different metabolic pathways. [ABSTRACT FROM AUTHOR]

Photofermentative hydrogen production from crop residues, if feasible, can lead to complete conversion of organic substances to hydrogen (and carbon dioxide). This mini review lists the studies on photofermentative hydrogen production using crop residues as feedstock. Pretreatment methods, substrate structure, mechanism of photosynthetic bacteria growth and metabolism were discussed. Photofermentative hydrogen production from pure culture, consortia and mutants, and the geometry, light sources, mass transfer resistances and the operational strategies of the photo-bioreactor were herein reviewed. Future studies of regulation mechanism of photosynthetic bacteria, such as highly-efficient strain breeding and gene reconstruction, and development of new-generation photo-bioreactor were suggested. [ABSTRACT FROM AUTHOR]

In this study, photosynthetic bacteria (PSB) were first harvested by MBR with pendulum type oscillation (PTO) hollow fiber module in succession and on a large scale. Based on unique properties of PSB, PSB/MBR was successfully applied for high-salinity wastewater treatment. Compared with control PSB-MBR (CMBR), PSB/PTO-MBR exhibited more excellent organics removal, which was mainly attributed to much higher biomass production for utilization. Meanwhile, the influence of light irradiation and aeration on activity of PSB was investigated in detail. Results showed that PTO-MBR with 12 h light irradiation proved to be a promising and economical alternative. The cycle of dark/light and anoxic had a positive effect on PSB cultivating. Moreover, PTO-MBR exhibited much higher flux than CMBR even if large amounts of biomass existed, which demonstrated that the strong shear stress on interface of liquid-membrane played important roles on membrane fouling reduction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrolysis temperature strongly affects C, N release, and solids destruction. • Thermal hydrolysis in batch mode is most efficient at 180 °C and 15 min. • Temperature increases the maximum BMP obtaining up to 380 LCH 4 /kgVS. • 83% and 71 % of solid destruction and N recovery, respectively, are obtained. • The impact of TH + AD on the release step may be energy positive. Purple phototrophic bacteria (PPB) are a novel driver to recover organics and nutrients from wastewater by assimilative growth. Depending on the source, assimilated resources from the PPB biomass can still be recovered after a releasing step. Anaerobic digestion (AD) releases carbon and nutrients, but the release is incomplete. Thermal hydrolysis (TH) as a pretreatment before AD improves the digestibility, release, and subsequent recovery potentials. This work determines the effects of TH in batch and continuous modes regarding methane potential, nutrients' release efficiencies, volatile solids destruction, degradability, and hydrolysis rates. Continuous runs over 165 days (d) confirmed enhanced recovery potentials, achieving up to 380 LCH 4 /kgVS (83 % solids destruction) and 73 % N release, respectively. The TH pretreatment is energy-intensive, but with appropriate heat recovery and increased methane production in the AD of the pretreated biomass, a combined configuration is energy positive. [ABSTRACT FROM AUTHOR]

Two strains of photosynthetic bacteria, Rhodobacter blasticus and Rhodobacter capsulatus , were used in this work to investigate the feasibility of using photosynthetic bacteria for the treatment of anaerobically digested swine wastewater. The effects of crucial factors which influence the pollutants removal efficiency were also examined. Results showed that anaerobically digested swine wastewater could be treated effectively by photosynthetic bacteria. The treatment efficiency was significantly higher by the mixed photosynthetic bacteria than that by any unitary bacterium. The optimal treatment condition by mixed bacteria was inoculation of 10.0% (v/v) of the two bacteria by 1:1, initial pH of 7.0 and initial chemical oxygen demand of 4800 mg L −1 . Under these conditions, the removal rate of chemical oxygen demand was 83.3%, which was 19.3% higher than when using Rhodobacter blasticus or 10.6% higher than when using Rhodobacter capsulatus separately. This mixed photosynthetic bacteria achieved high chemical oxygen demand removal and cell yields. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-culture of proper PSB and microalgae enhanced biomass and oil productivities. • Inoculation ratio affected the growth and oil productivity of co-culture. • PSB promoted the microalgal metabolism of organic carbon utilization. • PSB decreased the carbon dioxide utilization and photosynthesis of microalgae. Microalgae-photosynthetic bacteria (PSB) co-culture, which is promising for wastewater treatment and lipid production, is lacking of study. In this work, the combinations of 3 microalgae and 3 PSB strains were firstly screened and then different inoculation ratios of the co-cultures were investigated. It was found the best promotion was Chlorella pyrenoidosa/Rhodobacter capsulatus co-culture (1:1), where the biomass productivity, acetate assimilation rate and lipid productivity were 1.64, 1.61 and 2.79 times than that of the sum of pure microalgae and PSB cultures, respectively. Meanwhile, the inoculation ratio significantly affected the growth rate and lipid productivity of co-culture systems. iTRAQ analysis showed that PSB played a positive effect on acetate assimilation, TCA cycle and glyoxylate cycle of microalgae, but decreased the carbon dioxide utilization and photosynthesis, indicating PSB promoted the microalgae metabolism of organic carbon utilization and weakened inorganic carbon utilization. These findings provide in-depth understanding of carbon utilization in microalgae-PSB co-culture. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SCP yield was enhanced by PSB with fermentation liquid as carbon source. • Carbon source regulation promoted the growth and viability of PSB effectively. • PSB was favor to utilize the VFAs in fermentation liquid, especially acetic acid. • Carbon metabolic pathways involved in the SCP biosynthesis were improved. • Environmental behavior was stimulated to maintain high activity of PSB. Single cell protein (SCP) production by photosynthetic bacteria (PSB) is dependent on the bioavailability of carbon source, while sufficient volatile fatty acids (VFAs) in food waste fermentation liquid might be a potential alternative. It is unclear how the fermentation liquid affects the SCP biosynthesis and the related metabolic mechanism. This work demonstrated that the SCP production could be improved effectively (2088.4 mg/L) with high conversion capacity of carbon source (0.99 mg-biomass/mg-COD) by regulating carbon source level. PSB preferred to utilize the VFAs in food waste fermentation liquid. The carbon metabolic pathways (e.g., the transformation of VFAs to acetyl-CoA, and tricarboxylic acid cycle) involved in the SCP production were enhanced under optimal condition. Moreover, optimal carbon source regulation could significantly stimulate the environmental behaviour of PSB (e.g., two-component system, quorum sensing, and ATP-binding cassette transporter) involved in adaptation to external stimulus and maintaining high bacterial activity, resulting in SCP yield promotion. [ABSTRACT FROM AUTHOR]

Schematic diagram of how PSB biodegrade 4-CP with the synergistic effect of varied microorganisms such as the phyla of Proteobacteria , Firmicutes and Bacteroidetes. [Display omitted] • Photosynthetic bacteria (PSB) have a good patience of salinity. • PSB subculturing in absence of NaCl can save 50% inoculation time. • PSB cometabolic system with exogeneous carbon sources for 4-CP degradation. • A new 4-CP degradation way in PSB system is proposed. 4-chlorophenol (4-CP) as a toxic persistent pollutant is quite difficult treatment by using traditional biological processes. Herein, photosynthetic bacteria (PSB) driven cometabolic biodegradation system associated with exogeneous carbon sources (e.g. , sodium acetate) has been demonstrated as an effective microbial technique. The biodegradation rate (r i) can be at 0.041 d−1 with degradation efficiency of 93% in 3094 lx. Through the study of subculturing PSB in absence of NaCl, it was found that 50% inoculation time can be saved but keeping a similar 4-CP biodegradation efficiency in scale-up salinity system. A new plausible biodegradation pathway for 4-CP in 4th G PSB cometabolic system is proposed based on the detected cyclohexanone generation followed by ring opening. It is probably ascribed to the increasement of Firmicutes and Bacteroidetes at phyla level classified based on microbial community. This study contributes to a new insight into cometabolic technology for chlorophenol treatment in industrial hypersaline wastewater. [ABSTRACT FROM AUTHOR]

A consensus is lacking whether monochromatic rather than broad-spectrum illumination is more efficient for photosynthetic microbe production platforms. Light wavelength and intensity were tuned to pigment composition for growth of the Cyanobacterium Synechocystis PCC 6803. Phycocyanin (PC)-targeting LEDs (620 nm) provided more than 6 times the peak efficiency of white LEDs, with peak efficiency growth rates of 0.063 h −1 at 81 μE m −2 s −1 and 0.039 h −1 at 126 μE m −2 s −1 for red and white LEDs, respectively. Chlorophyll a (Chl a )-targeting LEDs (680- and 440-nm) performed poorly. Indeed, 10 times greater mass abundance was observed for PC than Chl a . PC levels did not change while Chl a levels decreased when Synechocystis transitioned from white light at 50 μE m −2 s −1 to 250 μE m −2 s −1 with 620 nm, 680 nm, or white LEDs. This work demonstrates that light wavelengths and intensity need to be optimized for each strain. [ABSTRACT FROM AUTHOR]

Flux Balance Analysis was performed with the Genome Scale Metabolic Model of a fast growing cyanobacterium Synechococcus sp. PCC 7002 to gain insights that would help in engineering the organism as a production host. Gene essentiality and synthetic lethality analysis revealed a reduced metabolic robustness under genetic perturbation compared to the heterotrophic bacteria Escherichia coli . Under glycerol heterotrophy the reducing equivalents were generated from tricarboxylic acid cycle rather than the oxidative pentose phosphate pathway. During mixotrophic growth in glycerol the photosynthetic electron transport chain was predominantly used for ATP synthesis with a photosystem I/photosystem II flux ratio higher than that observed under autotrophy. An exhaustive analysis of all possible double reaction knock outs was performed to reroute fixed carbon towards ethanol and butanol production. It was predicted that only ∼10% of fixed carbon could be diverted for ethanol and butanol production. [ABSTRACT FROM AUTHOR]

Suboptimal light and chemical distribution (CO 2 , O 2 ) in photobioreactors hinder phototrophic microalgal productivity and prevent economically scalable production of biofuels and bioproducts. Current strategies that improve illumination in reactors negatively impact chemical distribution, and vice versa. In this work, an integrated illumination and aeration approach is demonstrated using a gas-permeable planar waveguide that enables combined light and chemical distribution. An optically transparent cellulose acetate butyrate (CAB) slab is used to supply both light and CO 2 at various source concentrations to cyanobacteria. The breathable waveguide architecture is capable of cultivating microalgae with over double the growth as achieved with impermeable waveguides. [ABSTRACT FROM AUTHOR]

The electrochemical activity of two seawater microbial consortia were investigated in three-electrode bioelectrochemical cells. Two seawater inocula – from the Sunshine Coast (SC) and Gold Coast (GC) shores of Australia – were enriched at +0.6 V vs. SHE using 12/12 h day/night cycles. After re-inoculation, the SC consortium developed a fully-reversible cathodic/anodic current, with a max. of −62 mA m −2 during the day and +110 mA m −2 at night, while the GC exhibited negligible daytime output but +98 mA m −2 at night. Community analysis revealed that both enrichments were dominated by cyanobacteria, indicating their potential as biocatalysts for indirect light conversion to electricity. Moreover, the presence of γ-proteobacterium Congregibacter in SC biofilm was likely related to the cathodic reductive current, indicating its effectiveness at catalysing cathodic oxygen reduction at a surprisingly high potential. For the first time a correlation between a dual microbial community and fully reversible current is reported. [ABSTRACT FROM AUTHOR]

[Display omitted] • Genetic engineering affects light transfer efficiency, enzyme activity and bacteria. • Immobilization maintains high microbial cell density and stable H 2 production. • Nanomaterials enhance nitrogenase activity, leading to higher H 2 yield. • Integrated process is promising for enhancing H 2 production. Clean energy like hydrogen can be a promising strategy to solve problems of global warming. Photo-fermentation (PF) is an attractive technology for producing biohydrogen from various biowastes cost-effectively and environmentally friendly. However, challenges of low light conversion efficiency and small yields of biohydrogen production still limit its application. Thus, advanced strategies have been investigated to enhance photo-fermentative biohydrogen production. This review discusses advanced technologies that show positive outcomes in improving biohydrogen production by PF, including the following. Firstly, genetic engineering enhances light transfer efficiency, change the activity of enzymes, and improves the content of ATP, ammonium and antibiotic tolerance of photosynthetic bacteria. Secondly, immobilization technology is refined. Thirdly, nanotechnology makes great strides as a scientific technique and fourthly, integration of dark and photo-fermentation technology is possible. Some suggestions for further studies to achieve high levels of efficiency of photo-fermentative biohydrogen production are mentioned in this paper. [ABSTRACT FROM AUTHOR]

This study aimed at enhancing the bacterial biomass and pigments production in together with pollution removal in photosynthetic bacteria (PSB) wastewater treatment via using different photoperiods. Different light/dark cycles and light/dark cycle frequencies were examined. Results showed that PSB had the highest biomass production, COD removal and biomass yield, and light energy efficiency with light/dark cycle of 2 h/1 h. The corresponding biomass, COD removal and biomass yield reached 2068 mg/L, 90.3%, and 0.38 mg-biomass/mg-COD-removal, respectively. PSB showed higher biomass production and biomass yield with higher light/dark cycle frequency. Mechanism analysis showed within a light/dark cycle from 1 h/2 h to 2 h/1 h, the carotenoid and bacteriochlorophyll production increased with an increase in light/dark cycle. Moreover, the pigment contents were much higher with lower frequency of 2–4 times/d. [ABSTRACT FROM AUTHOR]

Electrode materials play a vital role in biofilm formation and electron conduction for efficient functioning of fuel cells. In the present study, graphite polymer composite electrode (GPF) was evaluated as anode for photo-bioelectrocatalytic fuel cell (PhFC; biophotovoltaic system) and compared with much studied graphite electrode (Gc) with photosynthetic bacteria as biocatalyst under anoxygenic condition. The electrogenic activity noticed in GPF (584 mV; 2.67 mA) was slightly lower than Gc (604 mV; 2.92 mA; OL2/HRT2). Consequently, COD removal observed by GPF (87.3%) was lower than Gc (91.8%). The increase in bacterial chlorophyll pigment showed a positive influence on electrogenic activity for both the electrodes. The polarization resistance (OL2 and HRT2 condition) was significantly higher for GPF (330 Ω) as compared to Gc (110 Ω). It is interesting to note that the performance of GPF is slightly lower than Gc based PhFC. The findings have opened avenues for composite materials for PhFC. [ABSTRACT FROM AUTHOR]

This study is aimed at enhancing biomass and pigments production together with pollution removal in photosynthetic bacteria (PSB) wastewater treatment via different light sources. Red, yellow, blue, white LED and incandescent lamp were used. Results showed different light sources had great effects on the PSB. PSB had the highest biomass production, COD removal and biomass yield with red LED. The corresponding biomass, COD removal and biomass yield reached 2580 mg/L, 88.6% and 0.49 mg-biomass/mg-COD-removal, respectively. The hydraulic retention time of wastewater treatment could be shortened to 72 h with red LED. Mechanism analysis showed higher ATP was produced with red LED than others. Light sources could significantly affect the pigments production. The pigments productions were greatly higher with LED than incandescent lamp. Yellow LED had the highest pigments production while red LED produced the highest carotenoid/bacteriochlorophyll ratio. Considering both efficiency and energy cost, red LED was the optimal light source. [ABSTRACT FROM AUTHOR]

A future hydrogen economy requires the sustainable production of renewable hydrogen. One method to produce hydrogen from stored renewable energy could be through reformation of bioethanol. However, chemically catalyzed reformation processes, although well studied, still present a number of significant technical challenges. Here, bioreformation of ethanol to hydrogen by photofermentation with the photosynthetic bacterium Rhodopseudomonas palustris is described. Cultures were shown to tolerate up to 2% ethanol. An RSM (response surface methodology) was carried out in which three key factors, light intensity, and ethanol and glutamate concentrations were varied. The results showed that nearly 2 mol of H 2 could be obtained from one mole of ethanol, 33% of that theoretically possible. [ABSTRACT FROM AUTHOR]

This study investigated the feasibility of using photosynthetic bacteria (PSB) to produce biomass and carotenoid while treating wastewater. The effects of light intensity on the biomass, carotenoid and bacteriochlorophyll accumulation in together with pollutant removal were studied. Results showed that it was feasible to use PSB to treat wastewater as well as to produce biomass or carotenoid. 2000 lux was an optimal intensity for biomass production and COD removal, and the corresponding values were 2645 mg/L and 94.7%. 8000 lux was an optimal light intensity for carotenoid production (1.455 mg/L). Mechanism analysis displayed that the greater the bacteriochlorophyll and carotenoid were secreted, the lower the light conversion efficiency turned out to be. The highest light conversion efficiency was achieved at 500 lux; the ATP production, biomass production, and COD removal were the highest at 2000 lux, but the bacteriochlorophyll and carotenoid content were the lowest at 2000 lux. [ABSTRACT FROM AUTHOR]

[Display omitted] • Process of microbial granule formation and microbial components of mature granules. • Important enzymes useful in the Hydrogen production have ben briefly discussed. • Granular Hydrogen productions by different type of granules have been tabulated. • Molecular engineering and other options for improving H 2 production. Microbes recycling nutrient and detoxifying ecosystems are capable to fulfil the future energy need by producing biohydrogen by due to the coupling of autotrophic and heterotrophic microbes. In granules microbes mutualy exchanging nutrients and electrons for hydrogen production. The consortial biohydrogen production depend upon constituent microbes, their interdependence, competition for resources, and other operating parameters while remediating a waste material in nature or bioreactor. The present review deals with development of granular algae-bacteria consortia, hydrogen yield in coculture, important enzymes and possible engineering for improved hydrogen production. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ultrasound of 0.3W/cm2 for 1min at the 0th and 27th hour was the optimal. [•] Cost of ultrasound was only 1% of the incremental sales value of cells. [•] Cell production was improved by 110% with low-strength ultrasound. [•] Ultrasound irradiation for over 10min damaged the bacteria. [Copyright &y& Elsevier]

Highlights: [•] The biocathode BES with PSB could enhance the dechlorination at cathode. [•] Light responses were performed to ascertain the role of PSB. [•] Dechlorination and mineralization were achieved with sequential biocathode–bioanode. [•] The performance could be improved with PSB inoculation in both cathode and anode. [ABSTRACT FROM AUTHOR]

Highlights: [•] Transposon mutagenesis was used to enhance H2 yield of a photosynthetic bacterium. [•] A transposon mutagenesis library of Rhodovulum sulfidophilum P5 was constructed. [•] Mutant TH-102 had higher aciduric and temperature resistant ability. [•] TH-102 can produce H2 at dark fermentation effluent environment (pH 5.5 and 35°C). [•] In continuous culture, H2 yield and rate were 17 and 15-fold higher than the WT. [ABSTRACT FROM AUTHOR]