Conversion of biogas to bioproducts by algae and methane oxidizing bacteria.

Biogas produced by anaerobic digestion is typically converted into electricity and low value heat. In this study, biogas is microbially transformed into valuable bioproducts. As proof of principle, the production of feed additives, i.e. lipids and polyhydroxybutyrate, out of biogas was evaluated. In a first stage, the CO2 in a synthetic biogas was photosynthetically fixed by an algae Scenedesmus sp. culture at an average rate of 192 ± 9 mg CO2 L⁻¹ liquid d⁻¹, resulting in concomitant O2 production. After N-depletion, more than 30% of the 220 ± 7 mg lipids g⁻¹ total organic carbon were unsaturated. In a second stage, the theoretical resulting gas mixture of 60% CH4 and 40% O2 was treated by a methane oxidizing Methylocystis parvus culture, with oxidation rates up to 452 ± 7 mg⁻¹ CH4-C L⁻¹ liquid d⁻¹. By repeated N-limitation, concentrations of 295 ± 50 mg intracellular polyhydroxybutyrate g⁻¹ cell dry weight were achieved. Finally, a one-stage approach with controlled coculturing of both microbial groups resulted in harvestable bioflocs. This is the first time that a total microbial conversion of both greenhouse gases into biomass was achieved without external O2 provision. Based on these results, a biotechnological approach is discussed whereby all kinds of biogas can be transformed into valuable bioproducts.

Convergent dynamics of the juvenile European sea bass gut microbiota induced by poly-ß-hydroxybutyrate.

Poly-ß-hydroxybutyrate (PHB) is a bacterial energy and carbon storage compound which exhibits a controlling effect on the gastrointestinal microbiota. Its beneficial activities for aquaculture have already been shown in terms of increased disease resistance and growth performance in a number of studies. However, the action of PHB on the intestinal microbial community in the treated animals has not yet been studied in depth. In this research, the effects of PHB on the microbiota composition in the intestinal tract of juvenile sea bass were examined. It was found that fish cohabiting in the same tank were on average 87% similar regarding the intestinal microbiota. When subjected to the same treatment and environmental conditions but reared in different tanks, the compositions of the enteric communities diverged. The provision of PHB overruled this tank effect by sustaining a microbial core community in the gut that represented 60% of the total bacterial diversity at the highest PHB level of 10%. The microbial community compositions converged between replicate tanks upon supplementation of PHB and were characterized by high dynamics and increased evenness. The results are discussed in the framework of hypotheses that try to relate the intestinal microbial community composition to the health status of the host organisms.

Denitrification in human dental plaque.

BACKGROUND: Microbial denitrification is not considered important in human-associated microbial communities. Accordingly, metabolic investigations of the microbial biofilm communities of human dental plaque have focused on aerobic respiration and acid fermentation of carbohydrates, even though it is known that the oral habitat is constantly exposed to nitrate (NO3-) concentrations in the millimolar range and that dental plaque houses bacteria that can reduce this NO3- to nitrite (NO2-). RESULTS: We show that dental plaque mediates denitrification of NO3- to nitric oxide (NO), nitrous oxide (N2O), and dinitrogen (N2) using microsensor measurements, 15N isotopic labelling and molecular detection of denitrification genes. In vivo N2O accumulation rates in the mouth depended on the presence of dental plaque and on salivary NO3- concentrations. NO and N2O production by denitrification occurred under aerobic conditions and was regulated by plaque pH. CONCLUSIONS: Increases of NO concentrations were in the range of effective concentrations for NO signalling to human host cells and, thus, may locally affect blood flow, signalling between nerves and inflammatory processes in the gum. This is specifically significant for the understanding of periodontal diseases, where NO has been shown to play a key role, but where gingival cells are believed to be the only source of NO. More generally, this study establishes denitrification by human-associated microbial communities as a significant metabolic pathway which, due to concurrent NO formation, provides a basis for symbiotic interactions.

Evaluation of biocathodes in freshwater and brackish sediment microbial fuel cells.

Biofilms on biocathodes can catalyze the cathodic oxygen reduction and accordingly guarantee high cathode redox potentials. The present research assessed the use of biocathodes in full-sediment microbial fuel cells. Carbon felt-based biocathodes were evaluated in freshwater systems, and an extension of their application to brackish systems and/or stainless steel webs as base material was considered. Efficient biocathodes could be developed within days through inoculation with active microorganisms. Carbon felt was found most suited for the biocathodes in freshwater with increased performance at salinities around 80-250 mM. Maximum long-term performance reached 12.3 microW cm(-2) cathode. The relative benefit of stainless steel seemed to increase with increasing salinity. A combination of stainless steel cathodes with biofilms could, however, also result in decreased electrical performance. In an efficiently catalyzing cathodic biofilm, an enrichment with an uncultured Proteobacterium--previously correlated with steel waste--was observed.

Poly-beta-hydroxybutyrate (PHB) increases growth performance and intestinal bacterial range-weighted richness in juvenile European sea bass, Dicentrarchus labrax.

The bacterial storage polymer poly-beta-hydroxybutyrate (PHB) has the potential to be used as an alternative anti-infective strategy for aquaculture rearing. In this research, the effects of (partially) replacing the feed of European sea bass juveniles with PHB were investigated. During a 6-week trial period, the PHB showed the ability to act as an energy source for the fish. This indicated that PHB was degraded and used during gastrointestinal passage. The gut pH decreased from 7.7 to 7.2 suggesting that the presence of PHB in the gut led to the increased production of (short-chain fatty) acids. The diets supplemented with 2% and 5% PHB (w/w) induced a gain of the initial fish weight with a factor 2.4 and 2.7, respectively, relative to a factor 2.2 in the normal feed treatment. Simultaneously, these treatments showed the highest bacterial range-weighted richness in the fish intestine. Based on molecular analysis, higher dietary PHB levels induced larger changes in the bacterial community composition. From our results, it seems that PHB can have a beneficial effect on fish growth performance and that the intestinal bacterial community structure may be closely related to this phenomenon.

Biological removal of 17alpha-ethinylestradiol by a nitrifier enrichment culture in a membrane bioreactor.

Increasing concern about the fate of 17alpha-ethinylestradiol (EE2) in the environment stimulates the search for alternative methods for wastewater treatment plant (WWTP) effluent polishing. The aim of this study was to establish an innovative and effective biological removal technique for EE2 by means of a nitrifier enrichment culture (NEC) applied in a membrane bioreactor (MBR). In batch incubation tests, the microbial consortium was able to remove EE2 from both a synthetic minimal medium and WWTP effluent. A maximum EE2 removal rate of 9.0 microg EE2 g(-1)biomass-VSS h(-1) was achieved (>94% removal efficiency). Incubation of the heterotrophic bacteria isolated from the NEC did not result in a significant EE2 removal, indicating the importance of nitrification as driving force in the mechanism. Application of the NEC in a MBR to treat a synthetic influent with an EE2 concentration of 83 ng EE2 L(-1) resulted in a removal efficiency of 99% (loading rates up to 208 ng EE2 L(-1)d(-1); membrane flux rate: 6.9 L m(-2) h(-1)). Simultaneously, complete nitrification was achieved at an optimal ammonium influent concentration of 1.0 mg NH(4)(+)-N L(-1). This minimal NH(4)(+)-N input is very advantageous for effluent polishing since the concomitant effluent nitrate concentrations will be low as well and it offers opportunities for the nitrifying MBR as a promising add-on technology for WWTP effluent polishing.

Poly-beta-hydroxybutyrate-accumulating bacteria protect gnotobiotic Artemia franciscana from pathogenic Vibrio campbellii.

A poly-beta-hydroxybutyrate (PHB)-accumulating enrichment culture was obtained using activated sludge from a polyphosphate-accumulating reactor as inoculum. PHB accumulated by the enrichment culture significantly enhanced the survival of Artemia nauplii, infected with the virulent pathogen Vibrio campbellii LMG 21363. A strain was isolated from the enrichment culture, based on its ability to accumulate PHB, and 16S rRNA gene sequencing of the isolate revealed 99% sequence similarity to Brachymonas denitrificans AS-P1. The isolate, named PHB2, showed good PHB-accumulating activity (up to 32% of the cell dry weight). PHB accumulated by isolate PHB2 was able to protect Artemia completely from the V. campbellii strain. Our data indicate that PHB-accumulating bacteria, such as B. denitrificans PHB2, could be used as an an effective and economically interesting alternative strategy to control infections in aquaculture.

Use of flow cytometry for analysis of phage-mediated killing of Enterobacter aerogenes.

In this study, the use of flow cytometry to analyze phage-mediated killing of Enterobacter aerogenes under varying conditions of temperature and nutrient availability was assessed. Bacteriophage UZ1, specific for an E. aerogenes strain, was applied at a multiplicity of infection (MOI) of 1 and 1000 to a Teflon surface, artificially infected with its host at a level of 4.5 log cells. After incubation for 20 h, bacteriophages were quantified using the soft agar layer method. For the quantification of bacterial cells, plate counting and flow cytometric analysis of live/dead stained cells were performed in parallel. At an MOI of 1, phage treatment was successful only after incubation under nutrient-rich conditions at 37 degrees C: E. aerogenes cells were not detected and a tenfold increase in phage UZ1 was observed. At a MOI of 1000, no E. aerogenes cells could be cultured after incubation at 37 and 4 degrees C. However, flow cytometric analysis revealed that lysis did not occur at 4 degrees C but was achieved during subsequent plate culture. In conclusion, the use of flow cytometry enabled identification of culture-based bias during plate culture. The flow cytometric assay used in this study proved to be rapid, as this culture-independent method does not require lengthy incubation periods post-sampling. The bacteriophage-mediated killing of E. aerogenes cells on Teflon surfaces indicated that disinfection of E. aerogenes with bacteriophage UZ1 can be successful when high MOIs are achieved, while at low multiplicities of infection conditions favorable for phage replication are required.

Pretreatment of spent sulphite liquor via ultrafiltration and nanofiltration for bio-based succinic acid production.

Ultrafiltration and nanofiltration of spent sulphite liquor (SSL) has been employed to evaluate the simultaneous production of lignosulphonates and bio-based succinic acid using the bacterial strains Actinobacillus succinogenes and Basfia succiniciproducens. Ultrafiltration with membranes of 10, 5 and 3kDa molecular weight cut-off results in significant losses of lignosulphonates (26-50%) in the permeate stream, while nanofiltration using membrane with 500Da molecular weight cut-off results in high retention yields of lignosulphonates (95.6%) in the retentate stream. Fed-batch bioreactor cultures using permeates from ultrafiltrated SSL resulted in similar succinic acid concentration (27.5g/L) and productivity (0.4g/L/h) by both strains. When permeates from nanofiltrated SSL were used, the strain B. succiniciproducens showed the highest succinic acid concentration (33.8g/L), yield (0.58g per g of consumed sugars) and productivity (0.48g/L/h). The nanofiltration of 1t of thick spent sulphite liquor could lead to the production of 306.3kg of lignosulphonates and 52.7kg of succinic acid, whereas the ultrafiltration of 1t of thick spent sulphite liquor using a 3kDa membrane could result in the production of 237kg of lignosulphonates and 71.8kg of succinic acid when B. succiniproducens is used in both cases.

Evaluation of an integrated biorefinery based on fractionation of spent sulphite liquor for the production of an antioxidant-rich extract, lignosulphonates and succinic acid.

Spent sulphite liquor (SSL) has been used for the production of lignosulphonates (LS), antioxidants and bio-based succinic acid. Solvent extraction of SSL with isopropanol led to the separation of approximately 80% of the total LS content, whereas the fermentations carried out using the pretreated SSL with isopropanol led to the production of around 19g/L of succinic acid by both Actinobacillus succinogenes and Basfia succiniciproducens. Fractionation of SSL via nanofiltration to separate the LS and solvent extraction using ethyl acetate to separate the phenolic compounds produced a detoxified sugar-rich stream that led to the production of 39g/L of succinic acid by B. succiniciproducens. This fractionation scheme resulted also in the production of 32.4g LS and 1.15g phenolic-rich extract per 100g of SSL. Both pretreatment schemes removed significant quantities of metals and heavy metals. This novel biorefinery concept could be integrated in acidic sulphite pulping mills.

Anaerobic bioconversion of organic waste into biogas by hot water treatment at near-critical conditions: application in bioregenerative life support.

The feasibility of nearly-complete conversion of lignocellulosic waste (70% food crops, 20% faecal matter and 10% green algae) into biogas was investigated in the context of a Life Support Project. The treatment comprised a series of processes, i.e. a mesophilic laboratory scale CSTR (continuously stirred tank reactor), an upflow biofilm reactor and a hydrothermolysis system in near-critical water. By the one-stage CSTR, a biogas yield of 75% with a specific biogas production of 0.37 l biogas g(-1) VSS (volatile suspended solids) added at a HRT (hydraulic retention time) of 20 d was obtained. Biogas yields further increased with 10-15% at HRT > 20 d, indicating the hydrolysis of lignocellulose to be the rate-limiting conversion step. The solids present in the CSTR-effluent were subsequently treated by hot water treatment (T approximately 310-350 degrees C, p approximately 240 bar), resulting in effective carbon liquefaction (50-60% without and 83% with carbon dioxide saturation) and complete hygienisation of the residue. Subsequent anaerobic digestion of the hydrolysate allowed further conversion of 48-60% on COD (chemical oxygen demand) basis. Thus, the total process yielded biogas corresponding with a COD conversion up to 90% of the original organic matter. It appears that mesophilic digestion in conjunction with hydrothermolysis at near-critical conditions offers interesting features for (nearly) complete, non-toxic and hygienic carbon and energy recovery from human waste in a bioregenerative life support context.

Biogenic silver nanoparticles (bio-Ag 0) decrease biofouling of bio-Ag 0/PES nanocomposite membranes.

Biofouling is a major problem for the application of membrane technology in water and wastewater treatment. One of the practical strategies to decrease biofouling is the use of advanced anti-biofouling membrane material. In this study, different amounts of biogenic silver nanoparticles (bio-Ag(0)) were embedded in polyethersulfone (PES) membranes, using the phase-inversion method. The effects of the bio-Ag(0) content on the structure of the membrane and its filtration performance were systematically investigated. The results demonstrated that silver-containing nanostructures were uniformly distributed on membrane surface. Bio-Ag(0) incorporation slightly increased the hydrophilicity of the PES membrane and increased the permeate flux. The anti-bacterial and anti-biofouling properties of the bio-Ag(0)/PES nanocomposites membrane were tested with pure cultures (Escherichia coli and Pseudomonas aeruginosa) and a mixed culture (an activated sludge bioreactor), respectively. The bio-Ag(0)/PES composite membranes, even with the lowest content of biogenic silver (140 mg bio-Ag(0)m(-2)), not only exhibited excellent anti-bacterial activity, but also prevented bacterial attachment to the membrane surface and decreased the biofilm formation during a 9 weeks test.

Transparent exopolymer particle removal in different drinking water production centers.

Transparent exopolymer particles (TEP) have recently gained interest in relation to membrane fouling. These sticky, gel-like particles consist of acidic polysaccharides excreted by bacteria and algae. The concentrations, expressed as xanthan gum equivalents L⁻¹ (µg X(eq) L⁻¹), usually reach hundred up to thousands µg X(eq) L⁻¹ in natural waters. However, very few research was performed on the occurrence and fate of TEP in drinking water, this far. This study examined three different drinking water production centers, taking in effluent of a sewage treatment plant (STP), surface water and groundwater, respectively. Each treatment step was evaluated on TEP removal and on 13 other chemical and biological parameters. An assessment on TEP removal efficiency of a diverse range of water treatment methods and on correlations between TEP and other parameters was performed. Significant correlations between particulate TEP (>0.4 µm) and viable cell concentrations were found, as well as between colloidal TEP (0.05-0.4 µm) and total COD, TOC, total cell or viable cell concentrations. TEP concentrations were very dependent on the raw water source; no TEP was detected in groundwater but the STP effluent contained 1572 µg X(eq) L⁻¹ and the surface water 699 µg X(eq) L⁻¹. Over 94% of total TEP in both plants was colloidal TEP, a fraction neglected in nearly every other TEP study. The combination of coagulation and sand filtration was effective to decrease the TEP levels by 67%, while the combination of ultrafiltration and reverse osmosis provided a total TEP removal. Finally, in none of the installations TEP reached the final drinking water distribution system at significant concentrations. Overall, this study described the presence and removal of TEP in drinking water systems.

Degradation of acetaminophen by Delftia tsuruhatensis and Pseudomonas aeruginosa in a membrane bioreactor.

The incidence and fate of pharmaceuticals in the water cycle impose a growing concern for the future reuse of treated water. Because of the recurrent global use of drugs such as Acetaminophen (APAP), an analgesic and antipyretic drug, they are often detected in wastewater treatment plant (WWTP) effluents, receiving surface waters and drinking water resources. In this study, the removal of APAP has been demonstrated in a membrane bioreactor (MBR) fed with APAP as the sole carbon source. After 16 days of operation, at a hydraulic retention time (HRT) of 5 days, more than 99.9% removal was obtained when supplying a synthetic WWTP effluent with 100 µg APAP L(-1). Batch experiments indicated no sorption of APAP to the biomass, no influence of the WWTP effluent matrix, and the capability of the microbial consortium to remove APAP at environmentally relevant concentrations (8.3 µg APAP L(-1)). Incubation with allylthiourea, an ammonia monooxygenase inhibitor, demonstrated that the APAP removal was mainly associated with heterotrophic bacteria and not with the ammonia-oxidizing bacteria. Two APAP degrading strains were isolated from the MBR biomass and identified as Delftia tsuruhatensis and Pseudomonas aeruginosa. During incubation of the isolates, hydroquinone - a potentially toxic transformation product - was temporarily formed but further degraded and/or metabolized. These results suggest that the specific enrichment of a microbial consortium in an MBR operated at a high sludge age might be a promising strategy for post-treatment of WWTP effluents containing pharmaceuticals.

Biogenic metals for the oxidative and reductive removal of pharmaceuticals, biocides and iodinated contrast media in a polishing membrane bioreactor.

Pharmaceutical and personal care products, biocides and iodinated contrast media (ICM) are persistent compounds, which appear in ng to µg L(-1) in secondary effluents of sewage treatment plants (STPs). In this work, biogenic metals manganese oxides (BioMnOx) and bio-palladium (Bio-Pd) were applied in lab-scale membrane bioreactors (MBR) as oxidative and reductive technologies, respectively, to remove micropollutants from STP-effluent. From the 29 substances detected in the STP-effluent, 14 were eliminated in the BioMnOx-MBR: ibuprofen (>95%), naproxen (>95%), diuron (>94%), codeine (>93%), N-acetyl-sulfamethoxazole (92%), chlorophene (>89%), diclofenac (86%), mecoprop (81%), triclosan (>78%), clarithromycin, (75%), iohexol (72%), iopromide (68%), iomeprol (63%) and sulfamethoxazole (52%). The putative removal mechanisms were the chemical oxidation by BioMnOx and/or the biological removal by Pseudomonas putida and associated bacteria in the enriched biofilm. Yet, the removal rates (highest value: 2.6 µg diclofenac L(-1) d(-1)) need to improve by a factor 10 in order to be competitive with ozonation. ICM, persistent towards oxidative techniques, were successfully dehalogenated with a novel reductive technique using Bio-Pd as a nanosized catalyst in an MBR. Iomeprol, iopromide and iohexol were removed for >97% and the more recalcitrant diatrizoate for 90%. The conditions favorable for microbial H(2)-production enabling the charging of the Pd catalyst, were shown to be important for the removal of ICM. Overall, the results indicate that Mn oxide and Pd coupled to microbial catalysis offer novel potential for advanced water treatment.

Virus disinfection in water by biogenic silver immobilized in polyvinylidene fluoride membranes.

The development of innovative water disinfection strategies is of utmost importance to prevent outbreaks of waterborne diseases related to poor treatment of (drinking) water. Recently, the association of silver nanoparticles with the bacterial cell surface of Lactobacillus fermentum (referred to as biogenic silver or bio-Ag(0)) has been reported to exhibit antiviral properties. The microscale bacterial carrier matrix serves as a scaffold for Ag(0) particles, preventing aggregation during encapsulation. In this study, bio-Ag(0) was immobilized in different microporous PVDF membranes using two different pre-treatments of bio-Ag(0) and the immersion-precipitation method. Inactivation of UZ1 bacteriophages using these membranes was successfully demonstrated and was most probably related to the slow release of Ag(+) from the membranes. At least a 3.4 log decrease of viruses was achieved by application of a membrane containing 2500 mg bio-Ag(0)(powder) m(-2) in a submerged plate membrane reactor operated at a flux of 3.1 L m(-2) h(-1). Upon startup, the silver concentration in the effluent initially increased to 271 µg L(-1) but after filtration of 31 L m(-2), the concentration approached the drinking water limit ( = 100 µg L(-1)). A virus decline of more than 3 log was achieved at a membrane flux of 75 L m(-2) h(-1), showing the potential of this membrane technology for water disinfection on small scale.

PHB-degrading bacteria isolated from the gastrointestinal tract of aquatic animals as protective actors against luminescent vibriosis.

The use of poly-ß-hydroxybutyrate (PHB) was shown to be successful in increasing the resistance of brine shrimp against pathogenic infections. In this study, we isolated for the first time PHB-degrading bacteria from a gastrointestinal environment. Pure strains of PHB-degrading bacteria were isolated from Siberian sturgeon, European sea bass and giant river prawn. The capability of selected isolates to degrade PHB was confirmed in at least two of three setups: (1) growth in minimal medium containing PHB as the sole carbon (C) source, (2) production of clearing zones on minimal agar containing PHB as the sole C source and (3) degradation of PHB (as determined by HPLC analysis) in 10% Luria-Bertani medium containing PHB. Challenge tests showed that the PHB-degrading activity of the selected isolates increased the survival of brine shrimp larvae challenged to a pathogenic Vibrio campbellii strain by a factor 2-3. Finally, one of the PHB-degrading isolates from sturgeon showed a double biocontrol effect because it was also able to inactivate acylhomoserine lactones, a type of quorum-sensing molecule that regulates the virulence of different pathogenic bacteria. Thus, the combined supplementation of a PHB-degrading bacterium and PHB as a synbioticum provides perspectives for improving the gastrointestinal health of aquatic animals.

Removal of diatrizoate with catalytically active membranes incorporating microbially produced palladium nanoparticles.

There is an increasing concern about the fate of iodinated contrast media (ICM) in the environment. Limited removal efficiencies of currently applied techniques such as advanced oxidation processes require more performant strategies. The aim of this study was to establish an innovative degradation process for diatrizoate, a highly recalcitrant ICM, by using biogenic Pd nanoparticles as free suspension or immobilized in polyvinylidene fluoride (PVDF) and polysulfone (PSf) membranes. As measured by HPLC-UV, the removal of 20mg L(-1) diatrizoate by a 10mg L(-1) Pd suspension was completed after 4h at a pH of 10. LC-MS analysis provided evidence for the sequential hydrodeiodination of diatrizoate. Pd did not lose its activity after incorporation in the PVDF and PSf matrix and the highest activity (k(cat)=30.0+/-0.4h(-1) L g(-1) Pd) was obtained with a casting solution of 10% PSf and 500mg L(-1) Pd. Subsequently, water containing 20mg L(-1) diatrizoate was treated in a membrane contactor, in which the water was supplied at one side of the membrane while hydrogen was provided at the other side. In a fed batch configuration, a removal efficiency of 77% after a time period of 48h was obtained. This work showed that membrane contactors with encapsulated biogenic nanoparticles can be instrumental for treatment of water contaminated with diatrizoate.

Remediation of trichloroethylene by bio-precipitated and encapsulated palladium nanoparticles in a fixed bed reactor.

Trichloroethylene is a toxic and recalcitrant groundwater pollutant. Palladium nanoparticles bio-precipitated on Shewanella oneidensis were encapsulated in polyurethane, polyacrylamide, alginate, silica or coated on zeolites. The reactivity of these bio-Pd beads and zeolites was tested in batch experiments and trichloroethylene dechlorination followed first order reaction kinetics. The calculated k-values of the encapsulated catalysts were a factor of six lower compared to non-encapsulated bio-Pd. Bio-Pd, used as a catalyst, was able to dechlorinate 100 mgL(-1) trichloroethylene within a time period of 1h. The main reaction product was ethane; yet small levels of chlorinated intermediates were detected. Subsequently polyurethane cubes empowered with bio-Pd were implemented in a fixed bed reactor for the treatment of water containing trichloroethylene. The influent recycle configuration resulted in a cumulative removal of 98% after 22 h. The same reactor in a flow through configuration achieved removal rates up to 1059 mg trichloroethylene g Pd(-1)d(-1). This work showed that fixed bed reactors with bio-Pd polyurethane cubes can be instrumental for remediation of water contaminated with trichloroethylene.

The bacterial storage compound poly-beta-hydroxybutyrate protects Artemia franciscana from pathogenic Vibrio campbellii.

Infections caused by antibiotic-resistant luminescent Vibrios can cause dramatic losses in aquaculture. In this study, the short-chain fatty acid beta-hydroxybutyrate and its polymer poly-beta-hydroxybutyrate were investigated as possible new biocontrol agents. beta-Hydroxybutyrate was shown to completely inhibit the growth of pathogenic Vibrio campbelli at 100 mM. Moreover, the addition of 100 mM of this fatty acid to the culture water of Artemia nauplii infected with the V. campbelli strain significantly increased the survival of the nauplii. As Artemia is a non-selective and particle filter feeder, we also investigated whether poly-beta-hydroxybutyrate particles could be used to protect Artemia from the pathogenic V. campbellii. The addition of 100 mg l(-1) poly-beta-hydroxybutyrate or more to the Artemia culture water offered a preventive and curative protection from the pathogen as a significantly enhanced survival was noticed. If added as a preventive treatment, a complete protection of infected nauplii (no significant mortality compared with uninfected nauplii) was observed at 1000 mg l(-1) poly-beta-hydroxybutyrate. Our data indicate that the use of poly-beta-hydroxybutyrate might constitute an ecologically and economically sustainable alternative strategy to fight infections in aquaculture.