Strain Enterobacter Sp Research Articles

Uranium bioprecipitation mediated by a phosphate-solubilizing Enterobacter sp. N1-10 and remediation of uranium-contaminated soil

Uranium (U) pollution in soils is prevalent worldwide and poses a significant health risk that will require remediation approaches. However, traditional U bioreduction by sulfate reducing bacteria (SRB) are sensitive to oxygen and are not suitable for treating aerobic topsoil. Bioprecipitation of U into uranyl phosphate (UP) mediated by phosphate-solubilizing microorganism (PSM) is not affected by oxygen. In this study, PSM strains were isolated and used for U-contaminated soil remediation. Microbial metabolites and the mechanism of PSM bioprecipitation were revealed. The results showed that strain Enterobacter sp. N1-10 had the highest phosphate-solubilizing capacity (dissolved P was 409.51 ± 8.48 mg/L). Uranium bioprecipitation was investigated by culturing the bacterium in the presence of 50 mg/L U and in the cell-free culture supernatant. The results showed that strain N1–10 had a high U removal rate (99.45 ± 0.43 %) after adding 50 mg/L U to the culture medium. A yellow precipitate was immediately formed when uranyl nitrate solution was added to the cell-free culture supernatant. The analysis indicated that bacterium produced lactic acid (37.58 mg/L), citric acid (4.76 mg/L), succinic acid (2.03 mg/L), and D-glucuronic acid (1.94 mg/L); the four organic acids solubilized Ca3(PO4)2 to form stable uranyl phosphate precipitate. The application of strain N1-10 and Ca3(PO4)2 significantly decreased the bioavailability of soil U (43.54 ± 0.52 %). In addition, pot experiments showed that PSM N1-10 and Ca3(PO4)2 promoted plant growth and markedly reduced U accumulation by pakchoi. These results demonstrate that PSM N1-10 and Ca3(PO4)2 exhibit a great potential for U bioremediation.

Unveiling the performance of a novel alkalizing bacterium Enterobacter sp. LYX-2 in immobilization of available Cd

A novel alkalizing strain Enterobacter sp. LYX-2 that could resist 400 mg/L Cd was isolated from Cd-contaminated soil, which immobilized 96.05% Cd2+ from medium. Cd distribution analysis demonstrated that more than half of the Cd2+ was converted into extracellular precipitated Cd through mobilization of the alkali-producing mechanism by the strain LYX-2, achieving the high immobilization efficiency of Cd2+. Biosorption experiments revealed that strain LYX-2 had superior biosorption capacity of 48.28 mg/g for Cd. Pot experiments with Brassica rapa L. were performed with and without strain LYX-2. Compared to control, 15.92% bioavailable Cd was converted to non-bioavailable Cd and Cd content in aboveground vegetables was decreased by 37.10% with addition of strain LYX-2. Available Cd was mainly immobilized through extracellular precipitation, cell-surface biosorption and intracellular accumulation of strain LYX-2, which was investigated through Cd distribution, Scanning Electron Microscope and Energy-Dispersive X-ray Spectroscopy (SEM-EDS), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM) analysis. In addition, the application of strain LYX-2 significantly promoted the growth of vegetables about 2.4-fold. Above results indicated that highly Cd-resistant alkalizing strain LYX-2, as a novel microbial passivator, had excellent ability and reuse value to achieve the remediation of Cd-contaminated soil coupled with safe production of vegetables simultaneously.

Effect of Enterobacter sp. EG16 on Selenium biofortification and speciation in pak choi (Brassica rapa ssp. chinensis)

Using plant growth promoting rhizobacteria (PGPR) to boost Se uptake and accumulation in crops is a promising recent approach to biofortification. Most studies, however, have focused on a certain dose of PGPR or Se, while the synergistic effects of simultaneously changing the concentration of both exogenous Se and PGPR on plant growth and Se bioaccumulation are rarely explored. In this study, the combined treatments of 0-2 mg L−1 Se and (3.83-11.3) ×107 CFU mL−1 PGPR strain Enterobacter sp. EG16 were used for the hydroponic experiments of pak choi (Brassica rapa) to investigate the mutual effects on plant growth and Se absorption. The growth of pak choi, in terms of plant height, number of leaves and root tips, was promoted by combining 7.65×107 CFU mL−1 EG16 and no more than 1 mg L−1 of Se. Growth was significantly inhibited when the concentration of EG16 was raised to 11.3×107 CFU mL−1. Chlorophyll content, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities were also boosted under the same combination of Se and EG16 concentrations. In addition, the Se content of aboveground part and intact plants significantly increased with rising concentrations of EG16 and Se. Selenomethionine (SeMet), methylselenocysteine (SeMeCys) and selenocystine (SeCys2) were the main organo-Se compounds detected in pak choi, accounting for almost 90% when supplied with selenite. Among these compounds, SeMet accounted for a high proportion and SeCys2 for a relatively low percentage in most treatments. The two forms were inversely related, probably because the transformation was driven by EG16. On the other hand, the proportion of SeMeCys was significantly affected by different concentrations of exogenous Se and EG16. Selenate was also detected, indicative of selenite oxidation. In terms of both plant biomass and nutritional quality, the combined formulation of 1 mg L−1 Se and 7.65×107 CFU mL−1 of EG16 is a promising means of producing Se-enriched vegetables.

Genomic Clues of a Multidrug-Resistant Bacterium from Cultured Domestic Silkworm (Bombyx mori L.).

ABSTRACTEnterobacter sp. strain ASE was isolated from the gut of an infected domestic silkworm (Bombyx mori L.; Lepidoptera: Bombycidae). The whole-genome sequence (WGS) of the multidrug-resistant strain Enterobacter sp. ASE, which may contribute to our understanding of the strain’s antibiotic resistance mechanism and virulence properties.

The Characterization of an Efficient Phenylpyruvate Decarboxylase KDC4427, Involved in 2-Phenylethanol and IAA Production from Bacterial Enterobacter sp. CGMCC 5087.

ABSTRACTPhenylpyruvate decarboxylase (PPDC) is a crucial enzyme that plays important roles in 2-phenylethanol (2-PE) biosynthesis. In our previous study, we screened a highly efficient PPDC KDC4427 from the novel 2-PE-producing strain Enterobacter sp. CGMCC 5087. Meanwhile, its decarboxylation activity of indolylpyruvate (IPyA) was also higher than other indolylpyruvate decarboxylases (IPDCs) reported so far. In this study, KDC4427 protein was purified and characterized, and its catalytic mechanisms were analyzed by biological methods. The optimum pH and temperature of KDC4427 was pH 6.5 and 35°C, respectively. The enzyme activity was relatively stable between pH 6 and 8 and over the range of temperatures from 25°C to 45°C. KDC4427 showed the highest catalytic efficiency on phenylpyruvic acid (PPA); meanwhile, it also showed high activity for IPyA and 2-ketobutanoic acid, and it was found that KDC4427 belongs to IPDCs by phylogenetic tree analysis. The coverage of the three-dimensional structure of KDC4427 and EcIPDC from Enterobacter cloacae was 96%. Leucine 542, one of the residues in the substrate-binding pocket, is replaced by isoleucine in KDC4427 compared with EcIPDC. Site-directed mutagenesis showed that the transition from leucine to isoleucine was unlikely to make KDC4427 have high catalytic activity for PPA and IPyA; the mutants at glutamate 468 almost completely lost catalytic activities for both PPA and IPyA, indicating that this glutamate was essential for the catalytic activity. Additionally, alanine 387 plays an important role in the substrate selectivity of KDC4427.IMPORTANCE Compared with the chemical synthesis of 2-phenylethanol (2-PE) by condensation of ethylene oxide and benzene, the biological synthesis of 2-PE is a potential method to replace the traditional process. This makes biotransformation gradually become the main way to produce high-quality 2-PE. Phenylpyruvate decarboxylase (PPDC) is the critical enzyme in 2-PE biosynthesis, and it is a momentous point of penetration to increase the production of 2-PE. In this regard, KDC4427 can catalyze phenylpyruvic acid (PPA) to phenylacetaldehyde more efficiently than any other PPDC previously reported. Moreover, it has high activity of indolepyruvate decarboxylases (IPDCs), which will be a great breakthrough in the synthesis of indole-3-acetic acid (IAA). With this study, we offer insights into the KDC4427 catalytic mechanism and significantly expand the toolbox of available α-ketoacid decarboxylases for application in biosynthesis.

Insights into the genome sequence of the glyphosate-degrading bacterium Enterobacter sp. Bisph1

Abstract. Benserradj O, Benslama O, Ghorri S. 2021. Insights into the genome sequence of the glyphosate-degrading bacterium Enterobacter sp. Bisph1. Biodiversitas 23: 817-882. Glyphosate is by far the most extensively utilized herbicide in the world, and because of its negative effects on the environment and animal health, finding microorganisms with the ability to degrade this herbicide is one of the scientists’ top priorities. Enterobacter sp. Bisph1 was isolated during prospecting glyphosate-degrading bacteria from a sandy soil of the region of Biskra in Algeria. To better understand the involvement of this strain in the degradation of glyphosate, a sequencing of the 4.5 MB genome of Enterobacter sp. Bisph1, as well as an annotation, and analysis of its genome sequence were performed in this study. Genomic DNA was sequenced on a MiSeq sequencer llumina using paired-end sequencing with the Nextera XT protocol. The genome of strain Enterobacter sp. Bisph1 comprises one chromosome of 4,578,487 bp with a GC content of 53.6%. Its 4,330 genes (78.13%) were assigned a putative function. The genome contains two intact phages and no CRISPR was found. The genome inspection also revealed the presence of the carbon-to-phosphorus (C-P) bond lyase coding genes clusters that consists of eight genes phnFHIJKLMP. The draft genome of the Enterobacter sp. Bisph1 provides insight into the role of this strain as an important agent of bioremediation of glyphosate by examining the genes known to encode the biodegradation enzymes of this herbicide. The sequencing of the genome of Bisph1 allows a better understanding of the taxonomy of this strain within the Enterobacteriaceae family.

Efficient biodegradation of tetrabromobisphenol A by the novel strain Enterobacter sp. T2 with good environmental adaptation: Kinetics, pathways and genomic characteristics

T2, a gram-positive bacterium capable of rapidly degrading tetrabromobisphenol A (TBBPA), and affiliated with the genus Enterobacter, was isolated for the first time from sludge that had been contaminated for several years. The TBBPA degradation data fitted the first-order model well. Under optimal conditions (pH of 7, temperature of 31 °C, TBBPA concentration of 5 mg L−1, and inoculum size of 5%), 99.4% of the initially added TBBPA was degraded after 48 h. TBBPA degradation fitted the first-order model with the half-life of 3.3 h. These results illustrated that the TBBPA degradation capability of strain T2 was significantly better than that of previously reported bacteria. A total of 17 intermediates were detected, among which five were reported for the first time. Whole-genome sequencing revealed that strain T2 had a chromosome with the total length of 4 854 376 bp and a plasmid with the total length of 21 444 bp. It harbored essential genes responsible for debromination, such as cyp450, gstB, gstA, and HADH, and genes responsible for subsequent complete mineralization, such as bioC, yrrM, Tam, and Ubil. A key protein of haloacid dehalogenases responsible for the biodegradation of TBBPA may also be involved in the regulation of TBBPA degradation in natural environment. In soil bioremediation experiments, strain T2 showed excellent environmental adaptation. It was able to biodegrade TBBPA and its typical intermediate bisphenol A efficiently. Therefore, it could potentially be applied to treat TBBPA-contaminated sites.

Antimicrobial activity of phenolics isolated from the pruning wood residue of European plum (Prunus domestica L.)

European plum (Prunus domestica L.) is a tree cultivated in many countries for its edible fruits, and necessarily certain amounts of useless woody residues are generated every year during pruning works. The objectives of this research were to recover the phenolics present on that wood wastes and study their antimicrobial and antibiofilm activities against a selection of foodborne microorganisms, including multi-resistant strains. The isolation of components was carried out by combining fast centrifugal partition chromatography (FCPC) and semi-preparative high-performance liquid chromatography (HPLC), and the identification was achieved by conventional techniques. Nine compounds were identified: 2 flavan-3-ols [catechin (1) and epicatechin (2)]; 1 phenolic glucoside [annphenone (3)]; and 6 dimeric A-type proanthocyanidins (4–9). All of them have been reported in Prunus domestica by the first time in this work, with the exception of 1 and 2. Extracts, fractions and purified phenolics were submitted to antimicrobial and antibiofilm activity evaluations. The most significative antimicrobial effect was detected on the strain Enterobacter sp. UJA37p, previously isolated from organic tomato and with high tolerance to different biocides. All pure compounds showed MIC values of 100 μg/mL against this resistant bacterium. On the other hand, when bacteria were previously allowed to attach and form biofilm before treatments, we found interesting results in disruption of preformed biofilms with compound 7 [(+)-epiafzelechin-(2β→O→7,4β→8)-epicatechin], followed by compound 6 [(−)-ent-epiafzelechin-(2α→O→7,4α→8)-catechin] and compound 3 at a concentration of 0.1 μg/mL.

Confinement discerns swarmers from planktonic bacteria.

Powered by flagella, many bacterial species exhibit collective motion on a solid surface commonly known as swarming. As a natural example of active matter, swarming is also an essential biological phenotype associated with virulence, chemotaxis, and host pathogenesis. Physical changes like cell elongation and hyper-flagellation have been shown to accompany the swarming phenotype. Less studied, however, are the contrasts of collective motion between the swarming cells and their counterpart planktonic cells of comparable cell density. Here, we show that confining bacterial movement in circular microwells allows distinguishing bacterial swarming from collective swimming. On a soft agar plate, a novel bacterial strain Enterobacter sp. SM3 in swarming and planktonic states exhibited different motion patterns when confined to circular microwells of a specific range of sizes. When the confinement diameter was between 40 μm and 90 μm, swarming SM3 formed a single-swirl motion pattern in the microwells whereas planktonic SM3 formed multiple swirls. Similar differential behavior is observed across several other species of gram-negative bacteria. We also observed 'rafting behavior' of swarming bacteria upon dilution. We hypothesize that the rafting behavior might account for the motion pattern difference. We were able to predict these experimental features via numerical simulations where swarming cells are modeled with stronger cell-cell alignment interaction. Our experimental design using PDMS microchip disk arrays enabled us to observe bacterial swarming on murine intestinal surface, suggesting a new method for characterizing bacterial swarming under complex environments, such as in polymicrobial niches, and for in vivo swarming exploration.

Optimization of biotic and abiotic factors liable for biodegradation of chlorpyrifos and their modeling using neural network approaches

Chlorpyrifos has a substantial risk to human health besides biodiversity. In the present study, a previously isolated bacterial strain Enterobacter sp. SWLC2 has been used to investigate its biodegradation potential in different soil-slurries systems and to optimize culture conditions to achieve enhanced biodegradation of chlorpyrifos. The optimization results indicate that the maximum (87%) spiked-chlorpyrifos biodegradation occurred in a sandy loam soil-slurry system in aeration mode after 18 days of incubation at the optimal temperature (35 °C) and pH (7). The effect of sources of carbon/nitrogen (organic sugars, organic acids, and amino acids, etc.) on the biodegradation of chlorpyrifos has been investigated and their optimal values are estimated. The neural networks have been designed to find the optimal values of earlier factors in the predictive modeling of degradation of chlorpyrifos.

Root exudates influence chemotaxis and colonization of diverse plant growth promoting rhizobacteria in the pigeon pea – maize intercropping system

Intercropping, the co-cultivation of two or more plant species in the same field, has several advantages over growing only one plant species, however, the role of plant-microbe interactions in such a setup is poorly understood. To investigate the influence of rhizosphere colonization by plant growth-promoting rhizobacteria (PGPR) in an intercropping system, a model legume-cereal intercropping system involving maize (Zea mays) and pigeon pea (Cajanus cajan) was assessed for colonization using three different bacterial strains Enterobacter sp. C1D, Pseudomonas sp. G22, Rhizobium sp. IC3109. Cross colonization experiments suggested bacterial movement from one plant species to another in the presence/absence of a mesh barrier, implicating the role of intercrop root exudates. In vitro assays and plant inoculation studies displayed that Enterobacter sp. C1D had a preference for monocropped plants while Rhizobium sp. IC3109 to intercropped plants and Pseudomonas sp. G22 was evenly colonized in both conditions. Organic acids like fumarate, malate, and succinate, as analyzed by LC/MS/MS (MRM), were found to be prominent in monocropped plant root exudates, while co-cultivation resulted in a decrease of the exudation of these metabolites. The PGPR strains showed differential behavioral responses in terms of chemotaxis and biofilm formation towards root exudates of intercropped and monocropped plants. Overall, our study provides pieces of evidence that co-cultivation of legume and cereal plants leads to the variation in root exudates and the response of plant beneficial bacteria.

Purification and optimization of pink pigment produced by newly isolated bacterial strain Enterobacter sp. PWN1

Pigment-producing bacteria were isolated from kitchen wastewaters of the National Institute of Technology, Rourkela. A pink non-virulent bacterial strain PWN1 was selected based on the India Ink Broth and Coomassie Brilliant Blue (R-250) dye assay. According to morphological and biochemical characterization, the strain PWN1was a Gram-negative, rod-shaped, motile, non-coliform bacterium and could utilize only glucose and adonitol as sole carbon source. The pigment was found to be a growth-associated product, and the pigment production was accelerated after 40 h of bacterial culture. Further, 16S rRNA gene-based molecular identification showed its similarity with Enterobacter sp. The pigments were extracted by the solvent extraction method using chloroform and ethanol (3:1). The extracted pigments were then purified through thin-layer chromatography and column chromatography. To maximize pigment production, the culture condition was optimized for maximum biomass production using statistical software Design Expert v13. A quadratic model was structured describing the process efficiently and it suggested a moderate temperature, pH, and a high inoculum concentration which generated biomass of 3.81 ± 0.02 g/L. At optimized condition, 1 L of cell culture produced 3.77 g of biomass which produced a crude pigment of 0.234 g after solvent extraction and 0.131 g after column chromatography, implying a yield of 6.2% for crude pigment and 3.47% for purified pigment from biomass. The yield of the obtained pigment was high enough to draw interest for industrial production, although the application of the pigment is considerable for further study.

Interaction among endophytic bacteria, sweet sorghum (Sorghum bicolor) cultivars and chemical nitrogen fertilization.

The application of new agricultural technologies to attain sustainable production systems is necessary. The use of plant growth-promoting bacteria to improve plant growth and health has been studied for decades. This work aimed to isolate diazotrophic endophytic bacteria associated with sweet sorghum plants and study the interaction of their inoculation in combination with chemical N-fertilization on different sorghum cultivars. A bacterial collection of 181 isolates was constructed and characterized in vitro and in vivo. From that, the strains Enterobacter sp. UYSB89 and Kosakonia sp. UYSB139 were nifH+, produce IAA, defined as true endophytes and able to promote growth of two sweet sorghum under greenhouse conditions. The evaluated cultivars responded differentially to bacterial inoculation, the nitrogen fertilization doses and their interaction. Thus, plant growth is a multifactorial consequence of the interrelation between crop practices and the plant genotypes. This knowledge is a valuable factor in terms of understanding plant-bacteria endophyte interactions to preserve environmental sustainability during the implementation of agronomic practices.

Production of nisin-containing bacterial cellulose nanomaterials with antimicrobial properties through co-culturing Enterobacter sp. FY-07 and Lactococcus lactis N8

Bacterial cellulose (BC) is used in various fields for its unique physical properties, but does not have the antimicrobial properties needed for the food and biomedical industries. Co-culture fermentation is a method commonly used in biotechnology to address high costs. A nisin-containing BC film (BC-N) was obtained by co-cultivating the BC-producing strain Enterobacter sp. FY-07 with the nisin-producing strain Lactococcus lactis N8. The physical properties of BC-N were similar those of BC, but the BC-N film had a specific strong inhibitory effect on Gram-positive bacteria. The antibacterial mechanism of BC-N was pore formation, but the obtained BC-N film had no significant impact on mammalian cell viability. This study provides a low-cost, facile and efficient technique to confer BC with antimicrobial properties. This strategy can be applied to introduce other functions into BC, and develop applications for BC polymers.

Inorganic Phosphate Solubilization by a Novel Isolated Bacterial Strain Enterobacter sp. ITCB-09 and Its Application Potential as Biofertilizer

The excessive use of fertilizers in agriculture is mainly due to the recognized plant requirements for soluble phosphorus. This problem has limited the implementation of sustainable agriculture. A viable alternative is to use phosphate solubilizing soil microorganisms. This work aimed to isolate inorganic phosphorus-solubilizing bacteria from the soils of agroecosystems, to select and identify, based on sequencing and phylogenetic analysis of the 16S rRNA gene, the bacterium with the highest capacity for in vitro solubilization of inorganic phosphate. Additionally, we aimed to determine its primary phosphate solubilizing mechanisms and to evaluate its effect on Habanero pepper seedlings growth. A total of 21 bacterial strains were isolated by their activity on Pikovskaya agar. Of these, strain ITCB-09 exhibited the highest ability to solubilize inorganic phosphate (865.98 µg/mL) through the production of organic acids. This strain produced extracellular polymeric substances and siderophores that have ecological implications for phosphate solubilization. 16S rRNA gene sequence analysis revealed that strain ITCB-09 belongs to the genus Enterobacter. Enterobacter sp. ITCB-09, especially when immobilized in beads, had a positive effect on Capsicum chinense Jacq. seedling growth, indicating its potential as a biofertilizer.

A novel peroxiredoxin from the antagonistic endophytic bacterium Enterobacter sp. V1 contributes to cotton resistance against Verticillium dahliae

[Aims] To reveal the molecular mechanism of endophytic bacteria in Verticillium wilt-resistant cottons and deeply understand the interaction between soil and plants. [Methods] Active tracking screening was used for the isolation of antagonistic strain. Morphological and molecular analyses were conducted to determine its phenotypic and genotypic characteristics. MALDI-TOF/TOF MS was employed to identify the antifungal substance. Functional verification was performed by gene cloning, expression, knockout and complementation. [Results] Enterobacter sp. V1 was isolated from Verticillium-wilt-resistant cotton Xinhai 15, which showed significantly antagonistic abilities against cotton verticillium wilt. A peroxiredoxin named ProV1 with virulent against V. dahliae was obtained. The gene for the peroxiredoxin ProV1 was cloned, and the nucleotide sequence showed 85.5% similarity with peroxiredoxin C (WP 096152328) reported from E. hormaeche. The purified heterologously expressed ProV1 indicated strong inhibitory activities. Moreover, the suppression of V. dahliae also decreased in proV1 mutant strain compared with wild type strain. The inhibitory activities could be partially restored by a complementation of proV1 gene in the mutant strain. [Conclusion] The results of this study reveal that a novel peroxiredoxin from an endophytic bacterial strain Enterobacter sp. V1 can serve as a virulent factor against fungi V. dahliae, which helps understanding the interaction between endyphytic bacteria and plant pathogenic fungi, and improving the biological control of cotton Verticillium wilt.

Cadmium resistance mechanisms of a functional strain Enterobacter sp. DNB-S2, isolated from black soil in Northeast China

Enterobacter sp. DNB-S2 is an efficient DBP-degrading bacterial strain, which was proved to be highly resistant to cadmium (MIC was 12.5 mM) and the involved mechanisms were verified in this study. The results showed the maximu values of extracellular adsorbed and intracellular accumulated Cd2+ contents accounted for 24.67% and 4.78% of the initial Cd2+ content in the medium. The extreme low intracellular Cd accumulation reduced the risk of cadmium interfering with normal cell metabolism. TEM exhibited cell structure of DNB-S2 kept intact even at high Cd concentrations. Some precipitation particles were formed inside cells, which were further identified to be Cd–O–P, Cd (OH)2, CdCO3, and CdS by XPS. Furthermore, Cd resistant genes were predicted on DNB-S2 genome, and the presence of 11 alkaline phosphatase encoding genes provided genetic basis for the formation of cadmium phosphate precipitation, which illustrated intracellular precipitation is one of the important intracellular Cd detoxification mechanisms in strain DNB-S2. Noteworthily, 8 efflux proteins were annotated possibly responsible for cadmium efflux and they were all predicted located on cytoplasmic membrane. In a word, integrity of cell structure, the formation of cadmium precipitation and efficient exclusion primarily constitute Cd tolerance mechanisms of strain DNB-S2. This strain exhibits promising application to the bioremediation of cadmium-DBP contaminated bites.

Microbial enhanced oil recovery through deep profile control using a conditional bacterial cellulose-producing strain derived from Enterobacter sp. FY-07

BackgroundHeterogeneity of oil-bearing formations is one of major contributors to low oil recovery efficiency globally. Long-term water flooding will aggravate this heterogeneity by resulting in many large channels during the exploitation process. Thus, injected water quickly flows through these large channels rather than oil-bearing areas, which ultimately leads to low oil recovery. This problem can be solved by profile control using polymer plugging. However, non-deep profile control caused by premature plugging is the main challenge. Here, a conditional bacterial cellulose-producing strain, namely Enterobacter sp. FY-0701, was constructed for deep profile control to solve the problem of premature plugging. Its deep profile control and oil displacement capabilities were subsequently identified and assessed.ResultsThe conditional bacterial cellulose-producing strain Enterobacter sp. FY-0701 was constructed by knocking out a copy of fructose-1, 6-bisphosphatase (FBP) encoding gene in Enterobacter sp. FY-07. Scanning electron microscope observation showed this strain produced bacterial cellulose using glucose rather than glycerol as the sole carbon source. Bacterial concentration and cellulose production at different locations in core experiments indicated that the plugging position of FY-0701 was deeper than that of FY-07. Moreover, enhanced oil recovery by FY-0701 was 12.09%, being 3.86% higher than that by FY-07 in the subsequent water flooding process.ConclusionsTo our knowledge, this is the first report of conditional biopolymer-producing strains used in microbial enhance oil recovery (MEOR). Our results demonstrated that the conditional bacterial cellulose-producing strain can in situ produce biopolymer far from injection wells and plugs large channels, which increased the sweep volume of injection water and enhance oil recovery. The construction of this strain provides an alternative strategy for using biopolymers in MEOR.

A New Strategy for Effective Succinic Acid Production by Enterobacter sp. LU1 Using a Medium Based on Crude Glycerol and Whey Permeate.

The newly-isolated strain Enterobacter sp. LU1, which has previously been shown to be an effective producer of succinic acid on glycerol with the addition of lactose, was used for further intensive works aimed at improving the production parameters of the said process. The introduction of an initial stage of gentle culture aeration allowed almost 47 g/L of succinic acid to be obtained after 168 h of incubation, which is almost two times faster than the time previously taken to obtain this amount. Furthermore, the replacement of glycerol with crude glycerin and the replacement of lactose with whey permeate allowed the final concentration of succinic acid to be increased to 54 g/L. Considering the high content of yeast extract (YE) in the culture medium, tests were also performed with a reduced YE content via its partial substitution with urea. Although this substitution led to a deterioration of the kinetic parameters of the production process, using the fed-batch strategy, it allowed a succinic acid concentration of 69 g/L to be obtained in the culture medium, the highest concentration ever achieved using this process. Furthermore, the use of microaerophilic conditions meant that the addition of lactose to the medium was not required, with 37 g/L of succinic acid being produced on crude glycerol alone.

Growth management of white-rot fungus Phlebia brevispora improved degradation of high-molecular-weight polycyclic aromatic hydrocarbons.

The effect of co-culturing white-rot fungus Phlebia brevispora with growth-promoting bacterial strains Enterobacter sp. TN3W-14 and Pseudomonas sp. TN3W-8 on the degradation of polycyclic aromatic hydrocarbons (PAHs) was evaluated in liquid culture. In axenic cultures, P. brevispora strains TN3F and TMIC33929 showed high degradation of phenanthrene (> 98%) within 15days, and degraded 65% and 63% of pyrene, and 12% and 8% of benzo(a)pyrene, respectively. This low level of degradation ability toward benzo(a)pyrene was improved significantly by co-culturing the fungi with a mixture of bacterial strains TN3W-8 and TN3W-14 (mixed bacterial co-culture; MBC). Within 15days, P. brevispora TN3F with MBC achieved about 86% pyrene and 53% benzo(a)pyrene degradation; P. brevispora TMIC33929 with MBC showed 92% pyrene and 72% benzo(a)pyrene degradation. The MBC alone degraded little PAH, as its growth was inhibited by PAH; however, its co-culture with P. brevispora improved mycelial growth of the fungus, which led to improved degradation of the PAHs. A possible dihydrodiol metabolite of pyrene from fungal cultures suggests that hydroxylation was the first step in the degradation of pyrene by P. brevispora.