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Hydrocarbon and heavy metal pollution are amongst the most severe and prevalent environmental problems due to their toxicity and persistence. Bioremediation using microorganisms is considered one of the most effective ways to treat polluted sites. In the present study, we unveil the bioremediation potential of Brucella pituitosa strain BU72. Besides its ability to grow on multiple hydrocarbons as the sole carbon source and highly tolerant to several heavy metals, BU72 produces different exopolysaccharide-based surfactants (EBS) when grown with glucose or with crude oil as sole carbon source. These EBS demonstrated particular and specific functional groups as determined by Fourier transform infrared (FTIR) spectral analysis that showed a strong absorption peak at 3250 cm-1 generated by the -OH group for both EBS. The FTIR spectra of the produced EBS revealed major differences in functional groups and protein content. To better understand the EBS production coupled with the degradation of hydrocarbons and heavy metal resistance, the genome of strain BU72 was sequenced. Annotation of the genome revealed multiple genes putatively involved in EBS production pathways coupled with resistance to heavy metals genes such as arsenic tolerance and cobalt-zinc-cadmium resistance. The genome sequence analysis showed the potential of BU72 to synthesise secondary metabolites and the presence of genes involved in plant growth promotion. Here, we describe the physiological, metabolic, and genomic characteristics of Brucella pituitosa strain BU72, indicating its potential as a bioremediation agent.
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Pentachlorophenol (PCP) is a toxic compound, which is widely used as a wood preservative product and general biocide. It is persistent in the environment and has been classified as a persistent organic pollutant to be reclaimed in many countries. Bioremediation is an emerging approach to rehabilitating areas polluted by recalcitrant xenobiotics. In the present study, we evaluated the potential of three strains of Pseudomonas (P. putida S121, P. rhizophila S211, and P. fuscovagiceae S115) as bioremediation agents in depletion and detoxification of PCP in soil microcosms. PCP removal was effectively optimized using a central-composite experimental design and response surface methodology (RSM). The optimum conditions for maximum PCP removal yield (85 ± 5%) were: 500 mg/kg PCP concentration, 108 UFC/g soil inoculum size of each strain and 55 days incubation period. The bacterial strains, P. putida, P. rhizophila, and P. fuscovagiceae, showed good capability to tolerate and degrade PCP so that they could be successfully used in synergistic effect to treat PCP polluted soils.
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Pentaclorofenol , Pseudomonas , Microbiologia do Solo , Poluentes do Solo , Biodegradação Ambiental , Pentaclorofenol/metabolismo , Pseudomonas/metabolismo , Solo/química , Poluentes do Solo/metabolismoRESUMO
Here, we report the genomic features and the bioremediation potential of Halomonas desertis G11, a new halophilic species which uses crude oil as a carbon and energy source and displays intrinsic resistance to salt stress conditions (optimum growth at 10% NaCl). G11 genome (3.96â¯Mb) had a mean GC content of 57.82%, 3622 coding sequences, 480 subsystems and 64 RNA genes. Annotation predicted 38 genes involved in osmotic stress including the biosynthesis of osmoprotectants glycine-betaine, ectoine and osmoregulated periplasmic glucans. Genome analysis revealed also the versatility of the strain for emulsifying crude oil and metabolizing hydrocarbons. The ability of G11 to degrade crude oil components and to secrete a glycolipid biosurfactant with satisfying properties was experimentally confirmed and validated. Our results help to explain the exceptional capacity of G11 to survive at extreme desertic conditions, and highlight the metabolic features of this organism that has biotechnological and ecological potentialities.
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Genes Bacterianos , Halomonas/genética , Anotação de Sequência Molecular , Petróleo/microbiologia , Tensoativos , Biodegradação Ambiental , Clima Desértico , Halomonas/metabolismo , Petróleo/metabolismo , TunísiaRESUMO
In the last decade, attention to extreme environments has increased because of interests to isolate previously unknown extremophilic microorganisms in pure culture and to profile their metabolites. Microorganisms that live in extreme environments produce extremozymes and extremolytes that have the potential to be valuable resources for the development of a bio-based economy through their application to white, red, and grey biotechnologies. Here, we provide an overview of extremophile ecology, and we review the most recent applications of microbial extremophiles and the extremozymes and extremolytes they produce to biotechnology.
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Bactérias/enzimologia , Proteínas de Bactérias/química , Enzimas/química , Bactérias/química , Bactérias/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Biotecnologia , Estabilidade Enzimática , Enzimas/genética , Enzimas/metabolismoRESUMO
In this paper, starch was extracted from fresh pasta by-product (PS) and its chemical composition and physical and microscopic characteristics were determined. Commercial wheat starch (CS) was used as reference. In general, purity was similar between starches studied. However, others compounds such as protein, lipid and ash were significantly different. PS starch granules had large lenticular-shape (25-33 µm) and small spherical-shape (5-8 µm). The pH and color of PS starch were similar to those reported for CS starch. On the other hand, PS had higher water absorption capacity, viscosity and cooking stability than CS. The gelatinization temperature of PS was similar to that of CS (60 and 61 °C). At high temperature (90 °C) both starches had similar rheological behavior. The results achieved suggest that PS starch has potential for application in food systems requiring high processing temperatures such the manufacture of sugar snap cookie. The effects of PS starch addition on the dough making stage and the final cookie quality were analyzed. Improvements in dough cohesiveness (24 %) and springiness (10 %) were significant relative to those of CS dough. Texture profile analysis confirmed the rheological changes.
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Considering the current growing interest in new and improved enzymes for use in a variety of applications, the present study aimed to characterize a novel detergent-stable serine alkaline protease from the extremophilic actinobacterium Microbacterium metallidurans TL13 (MmSP) using a combined in silico and experimental approach. The MmSP showed a close phylogenetic relationship with high molecular weight S8 peptidases of Microbacterium species. Moreover, its physical and chemical parameters computed using Expasy's ProtParam tool revealed that MmSP is hydrophilic, halophilic and thermo-alkali stable. 3D structure modelling and functional prediction of TL13 serine protease resulted in the detection of five characteristic domains: [catalytic subtilase domain, fibronectin (Fn) type-III domain, peptidase inhibitor I9, protease-associated (PA) domain and bacterial Ig-like domain (group 3)], as well as the three amino acid residues [aspartate (D182), histidine (H272) and serine (S604)] in the catalytic subtilase domain. The extremophilic strain TL13 was tested for protease production using agricultural wastes/by-products as carbon substrates. Maximum enzyme activity (390 U/gds) was obtained at 8th day fermentation on potato peel medium. Extracellular extract was concentrated and partially purified using ammonium sulfate precipitation methodology (1.58 folds purification fold). The optimal pH, temperature and salinity of MmSP were 9, 60 °C and 1 M NaCl, respectively. The MmSP protease showed broad pH stability, thermal stability, salt tolerance and detergent compatibility. In order to achieve the maximum stain removal efficacy by the TL 13 serine protease, the operation conditions were optimized using a Box-Behnken Design (BBD) with four variables, namely, time (15-75 min), temperature (30-60 °C), MmSP enzyme concentration (5-10 U/mL) and pH (7-11). The maximum stain removal yield (95 ± 4%) obtained under the optimal enzymatic operation conditions (treatment with 7.5 U/mL of MmSP during 30 min at 32 °C and pH9) was in good agreement with the value predicted by the regression model (98 ± %), which prove the validity of the fitted model. In conclusion, MmSP appears to be a good candidate for industrial applications, particularly in laundry detergent formulations, due to its high hydrophilicity, alkali-halo-stability, detergent compatibility and stain removal efficiency.
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Intracellular thermostable esterase produced by the extremophilic Geodermatophilus obscurus G20 was purified to homogeneity by a heat treatment, followed by an anion-exchange chromatography, and then characterized. The molecular weight of the purified enzyme determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was shown to be approximatively 55 kDa. The enzyme showed an optimal activity between pH 8.0 and 9.0 and was stable in the pH range 7.0-10.0. Moreover, it is highly thermostable, with a residual activity greater than 90% after incubation at 80 °C for more than 10 h. The enzyme showed preference for esters of p -nitrophenol with short chain fatty acid. When the p -nitrophenyl acetate (C2) was used as substrate, the Michaelis-Menten constant (K(m) ) and maximum velocity for the reaction (V(max) ) of esterase were 400 µM and 2500 U/mg protein, respectively. The effect of phenylmethanesulphonyl fluoride (PMSF), a serine-specific inhibitor, on the enzyme activity suggested that the thermostable esterase belong to the serine hydrolase group. Because of its high thermostability, activity at alkaline pH, tolerance to methanol and various metal ions and specificity for short chain fatty acids, this enzyme showed high potential for use in biocatalysis. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).
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Actinobacteria/enzimologia , Esterases/química , Esterases/isolamento & purificação , Biocatálise , Estabilidade Enzimática , Esterases/metabolismo , Concentração de Íons de Hidrogênio , Íons/química , Cinética , Metais/química , Peso Molecular , Solventes/química , TemperaturaRESUMO
Microbial polyhydroxyalkanoates (PHA) are biodegradable and biocompatible bio-based polyesters, which are used in various applications including packaging, medical and coating materials. In this study, an extremophilic hydrocarbonoclastic bacterium, previously isolated from saline sediment in the Tunisian desert, has been investigated for PHA production. The accumulation of intracellular PHA granules in Halomonas desertis G11 was detected by Nile blue A staining of the colonies. To achieve maximum PHA yield by the strain G11, the culture conditions were optimized through response surface methodology (RSM) employing a Box-Behnken Design (BBD) with three independent variables, namely, substrate concentration (1-5%), inoculum size (1-5%) and incubation time (5-15 days). Under optimized conditions, G11 strain produced 1.5 g/L (68% of DCW) of PHA using glycerol as a substrate. Application of NMR (1H and 13C) and FTIR spectroscopies showed that H. desertis accumulated PHA is a poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV). The genome analysis revealed the presence of typical structural genes involved in PHBV metabolism including phaA, phaB, phaC, phaP, phaZ, and phaR, coding for acetyl-CoA acetyltransferase, acetoacetyl-CoA reductase, class I polyhydroxyalkanoates synthases, phasin, polyhydroxyalkanoates depolymerase and polyhydroxyalkanoates synthesis repressor, respectively. Glycerol can be metabolized to 1) acetyl-CoA through the glycolysis pathway and subsequently converted to the 3HB monomer, and 2) to propionyl-CoA via the threonine biosynthetic pathway and subsequently converted to the 3HV monomer. In silico analysis of PhaC1 from H. desertis G11 indicated that this enzyme belongs to Class I PHA synthase family with a "lipase box"-like sequence (SYCVG). All these characteristics make the extremophilic bacterium H. desertis G11 a promising cell factory for the conversion of bio-renewable glycerol to high-value PHBV.
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Bioremediation offers a viable alternative for the reduction of contaminants from the environment, particularly petroleum and its recalcitrant derivatives. In this study, the ability of a strain of Pseudomonas BUN14 to degrade crude oil, pristane and dioxin compounds, and to produce biosurfactants, was investigated. BUN14 is a halotolerant strain isolated from polluted sediment recovered from the refinery harbor on the Bizerte coast, north Tunisia and capable of producing surfactants. The strain BUN14 was assembled into 22 contigs of 4,898,053 bp with a mean GC content of 62.4%. Whole genome phylogeny and comparative genome analyses showed that strain BUN14 could be affiliated with two validly described Pseudomonas Type Strains, P. kunmingensis DSM 25974T and P. chloritidismutans AW-1T. The current study, however, revealed that the two Type Strains are probably conspecific and, given the priority of the latter, we proposed that P. kunmingensis DSM 25974 is a heteronym of P. chloritidismutans AW-1T. Using GC-FID analysis, we determined that BUN14 was able to use a range of hydrocarbons (crude oil, pristane, dibenzofuran, dibenzothiophene, naphthalene) as a sole carbon source. Genome analysis of BUN14 revealed the presence of a large repertoire of proteins (154) related to xenobiotic biodegradation and metabolism. Thus, 44 proteins were linked to the pathways for complete degradation of benzoate and naphthalene. The annotation of conserved functional domains led to the detection of putative genes encoding enzymes of the rhamnolipid biosynthesis pathway. Overall, the polyvalent hydrocarbon degradation capacity of BUN14 makes it a promising candidate for application in the bioremediation of polluted saline environments.
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Genoma Bacteriano , Pseudomonas/genética , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Cromatografia Gasosa , Dioxinas/química , Dioxinas/metabolismo , Sedimentos Geológicos/microbiologia , Hidrocarbonetos/química , Hidrocarbonetos/metabolismo , Naftalenos/metabolismo , Filogenia , Pseudomonas/classificação , Pseudomonas/isolamento & purificação , Pseudomonas/metabolismo , Tensoativos/metabolismo , TunísiaRESUMO
In this work, a native exopolysaccharide (nEPS) produced by Halomonas desertis G11 isolated from a Tunisian extreme environment was modified by gamma irradiation. Characterization as well as the antioxidant and antitumor activities of nEPS and its gamma-irradiated derivatives (iEPSs) were comparatively evaluated. In vitro and in vivo antioxidant potentials were determined by using different methods and through different antioxidant enzymes. The antitumor activity was checked against a human colon cancer cell line. Analyses of the complete genome sequence were carried out to identify genes implicated in the production of nEPS. Thus, the genomic biosynthesis pathway and the export mechanism of nEPS were proposed. Analyses of irradiation data showed that iEPSs acquired new functional groups, lower molecular weights, and gained significantly (p < 0.05) higher antioxidant and antitumor abilities compared with nEPS. These findings provide a basis for using iEPSs as novel pharmaceutical agents for human therapies.
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The present study was intended toward the optimization of a textile dye Novacron Red decolorization by single and mixed culture of Bacillus strains namely, B. firmus, B. filamentosus and B. subterraneus. Optimization of dye decolorization using Bacillus monocultures was conducted using central composite design. The maximum dye decolorization achieved under optimized conditions for B. firmus, B. filamentosus and B. subterraneus was 89.24%, 88.28% and 88.45%, respectively. The effect of various consortia of selected Bacillus strains on dye removal was evaluated by applying a mixture design. The best dye (100 mg/L) decolorization yield (84%) was achieved using the consortium of B. filamentosus and B. subetrraneus.The Fourier Transform Infrared Spectroscopy analyses confirmed biodegradation potential of the two Bacillus strains. The results highlighted the potential of mono- and co-cultures of Bacillus strains for application in textile wastewater treatment. PRACTITIONER POINTS: Novel dye-decolorizing Bacillus strains were isolated from marine sediment. Optimization of decolorization was conducted using response surface methodology. Efficient decolorization of textile dye by Bacillus strains on mono- and co-cultures. The efficiency of the consortium B. filamentosus and B. subetrraneus on dye removal.
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Compostos Azo , Corantes , Bactérias , Biodegradação Ambiental , TêxteisRESUMO
The textile and clothing industry is the first manufacture sector in Tunisia in terms of employment and number of enterprises. It generates large volumes of textile dyeing wastewater (TDWW) containing high concentrations of saline, alkaline, and recalcitrant pollutants that could fuel tenacious and resilient electrochemically active microorganisms in bioanodes of bioelectrochemical systems. In this study, a designed hybrid bacterial halothermotolerant bioanode incorporating indigenous and exogenous bacteria from both hypersaline sediment of Chott El Djerid (HSCE) and TDWW is proposed for simultaneous treatment of real TDWW and anodic current generation under high salinity. For the proposed halothermotolerant bioanodes, electrical current production, chemical oxygen demand (COD) removal efficiency, and bacterial community dynamics were monitored. All the experiments of halothermotolerant bioanode formation have been conducted on 6 cm2 carbon felt electrodes polarized at -0.1 V/SCE and inoculated with 80% of TDWW and 20% of HSCE for 17 days at 45°C. A reproducible current production of about 12.5 ± 0.2 A/m2 and a total of 91 ± 3% of COD removal efficiency were experimentally validated. Metagenomic analysis demonstrated significant differences in bacterial diversity mainly at species level between anodic biofilms incorporating allochthonous and autochthonous bacteria and anodic biofilm containing only autochthonous bacteria as a control. Therefore, we concluded that these results provide for the first time a new noteworthy alternative for achieving treatment and recover energy, in the form of a high electric current, from real saline TDWW.
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The production, characterization and potential application in heavy metals and dyes removal of a novel heteropolysaccharide-protein named, gpHb, produced by an Haloarchaeal strain Halogeometricum borinquense strain A52 were investigated. The highest gpHb yield of 13.96 ± 0.32â g/L was produced under optimized conditions by response surface methodology. We focused on the characteristics and flocculation performance of gpHb. An important attribute of protein with 16 protein types identified that occupied a total content of 50.2% in the gpHb. Additionally, carbohydrate that occupied 30.4% of the total bioflocculant content consisted of three monosaccharides. Fourier transform-infrared spectroscopy indicated the presence of carboxyl, hydroxyl, amine, amide, and sulphate groups. To further study flocculation activities, factors such as bioflocculant dosage, temperature, pH, salinity and cations addition were tested. In comparison to the chemical flocculant polyaluminium chloride, gpHb maintain high activity at large range of salinity and its flocculation activity was higher on both sides of pH 7. Addition of trivalent cation mainly Fe3+ enhances the flocculating rate indicating that the bioflocculant is negatively charged. Its practical applicability was established for heavy metals and dyes removal from saline aqueous solutions. The highest removal efficiency was observed with Cr3+ (91.4%) and Ni2+ (89.60%) and with basic blue 3 (83.8%) and basic red (78.6%). The excellent flocculation activity of gpHb under saline condition suggests its potential industrial utility for treatment of textile and tannery wastewaters.
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Corantes , Metais Pesados , Floculação , Concentração de Íons de Hidrogênio , Águas ResiduáriasRESUMO
Hexavalent chromium [Cr(VI)], widely generated by tannery activities, is considered among the most toxic substances and causes a serious damage for the environment and for human health. Interestingly, some microorganisms have a potential of bioremediation of chromium-contaminated wastewaters and soils through the reduction of Cr(VI) (soluble and harmful form) into Cr(III) (stable and non-toxic form). Here, we present the full genome sequence of a novel heavy-metal-resistant, plant growth-promoting bacterium (PGPB), Microbacterium metallidurans TL13, which was isolated from a Tunisian leather industry. The strain TL13 was resistant to many heavy metals, such as chromium, copper, nickel, cobalt, and arsenic. The 50% TL13 growth inhibitory concentration (IC50) values of HgCl2, CoCl2, K2Cr2O7, CuSO4, NiCl2, FeSO4, and Na2HAsO4 are 368, 445, 676, 1,590, 1,680, 4,403, and 7,007 mg/L, respectively, with the following toxicity order: HgCl2 > CoCl2 > K2Cr2O7 > CuSO4 > NiCl2 > FeSO4 > Na2HAsO4. This new strain was also able to promote the growth of the hybrid tomato (Elika F1) under chromium metal stress. Its whole genome sequence length was estimated to be 3,587,460 bp (3,393 coding sequences) with a G + C content of 70.7%. Functional annotation of the genome of TL13 revealed the presence of open reading frames (ORFs) involved in adaptation to metal stress, such as the chromate transport protein, cobalt-zinc-cadmium resistance protein, copper resistance protein, copper responsive transcriptional regulator, multidrug resistance transporters, arsenical resistance operon repressor, arsenate reductase, arsenic resistance protein, mercuric resistance operon regulatory protein, mercuric ion reductase, and organomercurial lyase. Moreover, genes for the production of glutathione peroxidase, catalase, superoxide dismutase, and thioredoxin reductase, which confer a higher tolerance to oxidative/metal stresses, were identified in TL13 genome. In addition, genes for heat shock tolerance, cold shock tolerance, glycine-betaine production, mineral phosphate solubilization, ammonia assimilation, siderophores, exopolysaccharides, polyketides, and lytic enzymes (cellulase, chitinase, and proteases) production that enable bacteria to survive biotic/abiotic stress and to promote plant growth and health were also revealed. Based on genome analysis and experimental approaches, strain TL13 appears to have evolved from various metabolic strategies and could play a role in ensuring sustainable environmental and agricultural systems.
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Purpose: To assess exopolysaccharides (EPS) of Bacillus siamensis CV5, isolated from irradiated roots of Cistanche violacea, for their induction by ionizing radiation (IR) and their antioxidant and radioprotective power.Materials and methods: Isolated bacteria from the roots of C. violacea were screened for EPS production. The most EPS-producing bacterium was selected and the response surface methodology (RSM) was applied to elucidate the IR dose effects on EPS production. Gamma irradiation effects on the morphology and functional groups of EPS were studied using microscopy and Fourier transform infra-red (FT-IR). The radioprotective potential of EPS on the survival of B. siamensis CV5 following IR was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Free radicals scavenging potentialities (FRSP) of non-irradiated and irradiated EPS were evaluated through 2, 2--diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and ferric reducing ability of plasma (FRAP) assays.Results: Twenty strains, isolated from irradiated roots of C. violacea, were screened for their EPS production. IR-resistant B. siamensis CV5 was the most EPS-producing strain. Its purified EPS contained rhamnose, fructose, mannose and glucose. RSM indicated that EPS of CV5 (CV5-EPS) are radiation inducible. Micrographs of CV5-EPS suggested an increase in the total area and a decrease in the Feret's statistical diameter following exposure to IR. FT-IR spectra of these EPS revealed an increase of various functional groups. The MTT survival assay demonstrated a positive correlation between the added quantity of CV5-EPS and the viability of irradiated CV5 (p < .01). DPPH, ABTS and FRAP assays indicated that the antioxidant activities of CV5-EPS increased significantly with the irradiation dose (p < .01).Conclusions: CV5-EPS were demonstrated as radiation-inducible and radioprotective biomolecules. This radioprotective potential of CV5-EPS could be associated with their antioxidant activities. In the future, irradiated EPS could be tested as a gel in cancer radiotherapy for minimizing the damage caused by rays to surrounding healthy tissues.
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Bacillus/metabolismo , Bacillus/efeitos da radiação , Cistanche/microbiologia , Polissacarídeos Bacterianos/farmacologia , Protetores contra Radiação/farmacologia , Antioxidantes/química , Cistanche/efeitos da radiação , Sequestradores de Radicais Livres/farmacologia , Radicais Livres , Raios gama , Raízes de Plantas/microbiologia , Raízes de Plantas/efeitos da radiação , Doses de Radiação , Radiação IonizanteRESUMO
The main objective of this study was to understand the interaction between salinity, temperature and inoculum size and how it could lead to the formation of efficient halothermotolerant bioanodes from the Hypersaline Sediment of Chott El Djerid (HSCE). Sixteen experiments on bioanode formation were designed using a Box-Behnken matrix and response surface methodology to understand synchronous interactions. All bioanode formations were conducted on 6â¯cm2 carbon felt electrodes polarized at -0.1â¯V/SCE and fed with lactate (5â¯g/L) at pHâ¯7.0. Optimum levels for salinity, temperature and inoculum size were predicted by NemrodW software as 165â¯g/L, 45⯰C and 20%, respectively, under which conditions maximum current production of 6.98⯱â¯0.06â¯A/m2 was experimentally validated. Metagenomic analysis of selected biofilms indicated a relative abundance of the two phyla Proteobacteria (from 85.96 to 89.47%) and Firmicutes (from 61.90 to 68.27%). At species level, enrichment of Psychrobacter aquaticus, Halanaerobium praevalens, Psychrobacter alimentaris, and Marinobacter hydrocarbonoclasticus on carbon-based electrodes was correlated with high current production, high salinity and high temperature. Members of the halothermophilic bacteria pool from HSCE, individually or in consortia, are candidates for designing halothermotolerant bioanodes applicable in the bioelectrochemical treatment of industrial wastewater at high salinity and temperature.
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Fontes de Energia Bioelétrica/microbiologia , Firmicutes/fisiologia , Proteobactérias/fisiologia , Biofilmes , Eletrodos/microbiologia , Desenho de Equipamento , Firmicutes/genética , Firmicutes/isolamento & purificação , Genômica , Proteobactérias/genética , Proteobactérias/isolamento & purificação , Salinidade , TemperaturaRESUMO
A new bioflocculant named pKr produced by hydrocarbonoclastic strain Kocuria rosea BU22S (KC152976) was investigated. Gas chromatography-flame ionization detector (GC-FID) analysis confirmed the high potential of the strain BU22S in the degradation of n-alkanes. Plackett-Burman experimental design and response surface methodology were carried out to optimize pKr production. Glucose, peptone and incubation time were found to be the most significant factors affecting bioflocculant production. Maximum pKr production was about 4.72 ± 0.02â g/L achieved with 15.61â g/L glucose, 6.45â g/L peptone and 3 days incubation time. Chemical analysis of pKr indicated that it contained 71.62% polysaccharides, 16.36% uronic acid and 2.83% proteins. Thin layer chromatography analysis showed that polysaccharides fraction consisted of galactose and xylose. Fourier transform infrared analysis revealed the presence of many functional groups, hydroxyl, carboxyl, methoxyl, acetyl and amide that likely contribute to flocculation. K. rosea pKr showed high flocculant potential using kaolin clay at different pH (2-11), temperature (0-100°C) and cation concentrations. The bioflocculant was particularly effective in flocculating soluble anionic dyes, Reactive Blue 4 and Acid Yellow, with a decolorization efficiency of 76.4% and 72.6%, respectively. The outstanding flocculating performances suggest that pKr could be useful for bioremediation applications.
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Corantes/química , Polissacarídeos/química , Floculação , Concentração de Íons de Hidrogênio , Caulim , Temperatura , Purificação da ÁguaRESUMO
A total of 68 dimethoate and pentachlorophenol-tolerant rhizobacteria, isolated from a pesticide-contaminated agricultural soil, have been identified and typed by means of 16S-23S rRNA internal transcribed spacers analysis (ITS-PCR), 16S rRNA gene sequencing and by repetitive extragenic palindromic (BOX-PCR). The majority of bacterial isolates (84.31%) belonged to Proteobacteria (with a predominance of Gammaproteobacteria, 72.54%), while the remaining isolates were affiliated with Firmicutes (9.80%), Bacteroidetes (1.96%) and Actinobacteria (3.92%). The pesticide-tolerant bacterial isolates belonged to 11 genera, namely Pseudomonas, Bacillus, Acinetobacter, Flavobacterium, Comamonas, Achromobacter, Rhodococcus, Ochrobactrum, Aquamicrobium, Bordetella and Microbacterium. Within the well-represented genus Pseudomonas (n = 36), the most common species was Pseudomonas putida (n = 32). The efficacy of the selected strain, Pseudomonas putida S148, was further investigated for biodegradation of pentachlorophenol (PCP) in minimal medium, when used as a sole carbon and energy source. At an initial concentration of 100 mg/L, P. putida S148 degraded 91% of PCP after 7 days. GC-MS analyses revealed the formation of tetrachlorohydroquinone, tri- and di-chlorophenols as biodechlorination products in PCP remediation experiments. The toxicity estimation showed that 50% lethal concentration (LC50) and 50% growth inhibition concentration (IGC50) obtained values for the major identified compounds (2,3,4,6 tetrachlorophenol, 2,3,5,6 tetrachlorophenol and tetrachlorohydroquinone) were higher than those estimated for the PCP indicating that the metabolites are less toxic than the original compound for those specific organisms. S148 strain could be added to pesticide-contaminated agricultural soils as a bacterial inoculant for its potential to improve soil quality.
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This work describes the performance of a sequencing batch reactor (SBR) and the involvement of a novel reconstituted bacterial consortium in olive mill wastewater (OMW) treatment. The organic loading rate applied to the SBR was serially increased in terms of initial COD from 10 to 75 g L-1 to allow gradual acclimatization of activated sludge to high concentrations of toxic compounds in OMW. After the acclimatization period, up to 60% of the total COD content were effectively biodegraded from OMW at 75 g L-1 COD within 30 day hydraulic retention time. The diversity and community composition of cultivable bacteria participating in the aerobic process of treating OMW were further assessed. A total of 91 bacterial strains were isolated from the reactor and analyzed by amplification of the 16S-23S rRNA internal transcribed spacer (ITS) region and by 16S rRNA gene sequencing. The most abundant phylum was Firmicutes (57.1%) followed by Proteobacteria (35.2%) and Actinobacteria (7.7%). The use of the Biolog® Phenotype Microarray system to evaluate the ability of isolated strains to utilize OMW phenolic compounds is reported in this work for the first time. Interestingly, results showed that all species tested were able to utilize phenolics as sole carbon and energy sources. The removals of COD and phenolics from undiluted OMW by the reconstituted bacterial consortium were almost similar to those obtained by the acclimatized activated sludge, which suggest that cultivable bacteria play the major role in OMW biodegradation. Phytotoxicity assays using tomato seeds showed a significant improvement of seed germination values for treated OMW. Our overall results suggest that the novel developed bacterial consortium could be considered as a good prospect for phenolics-rich wastewaters bioremediation applications.
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A number of Pseudomonas strains function as inoculants for biocontrol, biofertilization, and phytostimulation, avoiding the use of pesticides and chemical fertilizers. Here, we present a new metabolically versatile plant growth-promoting rhizobacterium, Pseudomonas rhizophila S211, isolated from a pesticide contaminated artichoke field that shows biofertilization, biocontrol and bioremediation potentialities. The S211 genome was sequenced, annotated and key genomic elements related to plant growth promotion and biosurfactant (BS) synthesis were elucidated. S211 genome comprises 5,948,515 bp with 60.4% G+C content, 5306 coding genes and 215 RNA genes. The genome sequence analysis confirmed the presence of genes involved in plant-growth promoting and remediation activities such as the synthesis of ACC deaminase, putative dioxygenases, auxin, pyroverdin, exopolysaccharide levan and rhamnolipid BS. BS production by P. rhizophila S211 grown on olive mill wastewater based media was effectively optimized using a central-composite experimental design and response surface methodology (RSM). The optimum conditions for maximum BS production yield (720.80 ± 55.90 mg/L) were: 0.5% (v/v) inoculum size, 15% (v/v) olive oil mill wastewater (OMWW) and 40°C incubation temperature at pH 6.0 for 8 days incubation period. Biochemical and structural characterization of S211 BS by chromatography and spectroscopy studies suggested the glycolipid nature of the BS. P. rhizophila rhamnolipid was stable over a wide range of temperature (40-90°C), pH (6-10), and salt concentration (up to 300 mM NaCl). Due to its low-cost production, emulsification activities and high performance in solubilization enhancement of chemical pesticides, the indigenous BS-producing PGPR S211 could be used as a promising agent for environmental bioremediation of pesticide-contaminated agricultural soils.