Enhanced rice plant (BRRI-28) growth at lower doses of urea caused by diazinon mineralizing endophytic bacterial consortia and explorations of relevant regulatory genes in a Klebsiella sp. strain HSTU-F2D4R.

Endophytic biostimulant with pesticide bioremediation activities may reduce agrochemicals application in rice cultivation. The present study evaluates diazinon-degrading endophytic bacteria, isolated from rice plants grown in the fields with pesticide amalgamation, leading to increased productivity in high-yielding rice plants. These endophytes showed capabilities of decomposing diazinon, confirmed by FT-IR spectra analysis. Growth promoting activities of these endophytes can be attributed to their abilities to produce an increased level of IAA content and to demonstrate high level ACC-deaminase activities. Furthermore, these endophytes demonstrated enhanced level of extracellular cellulase, xylanase, amylase, protease and lignin degrading activities. Five genera including Enterobacter, Pantoea, Shigella, Acinetobacter, and Serratia, are represented only by the leaves, while four genera such as Enterobacter, Escherichia, Kosakonia, and Pseudomonas are represented only by the shoots. Five genera including, Klebsiella, Enterobacter, Pseudomonas, Burkholderia, and Bacillus are represented only by the roots of rice plants. All these strains demonstrated cell wall hydrolytic enzyme activities, except pectinase. All treatments, either individual strains or consortia of strains, enhanced rice plant growth at germination, seedling, vegetative and reproductive stages. Among four (I-IV) consortia, consortium-III generated the maximum rice yield under 70% lower doses of urea compared to that of control (treated with only fertilizer). The decoded genome of Klebsiella sp. HSTU-F2D4R revealed nif-cluster, chemotaxis, phosphates, biofilm formation, and organophosphorus insecticide-degrading genes. Sufficient insecticide-degrading proteins belonging to strain HSTU-F2D4R had interacted with diazinon, confirmed in molecular docking and formed potential catalytic triads, suggesting the strains have bioremediation potential with biofertilizer applications in rice cultivation.

Genome mining discovery of hydrogen production pathway of Klebsiella sp. WL1316 fermenting cotton stalk hydrolysate.

Genome sequencing was used to identify key genes for the generation of hydrogen gas through cotton stalk hydrolysate fermentation by Klebsiella sp. WL1316. Genome annotation indicated that the genome size was 5.2 Mb with GC content 57.6%. Xylose was metabolized in the pentose phosphate pathway via the conversion of xylose to xylulose in Klebsiella sp. WL1316. This strain contained diverse formate-hydrogen lyases and hydrogenases with gene numbers higher than closely related species. A metabolic network involving glucose, xylose utilisation, and fermentative hydrogen production was reconstructed. Metabolic analysis of key node metabolites showed that glucose and xylose metabolism influenced biomass synthesis and biohydrogen production. Formic acid accumulated during fermentation at 24-48 h but decreased sharply after 48 h, illustrating the splitting of formic acid to hydrogen gas during early-to-mid fermentation. The Kreb's cycle was the main competitive metabolic branch of biohydrogen synthesis at 24 h of fermentation. Lactic and acetic acid fermentation and late ethanol accumulation competed the carbon skeleton of biohydrogen synthesis after 72 h of fermentation, indicating that these competitive pathways are regulated in middle-to-late fermentation (48-96 h). This study is the first to elucidate the metabolic mechanisms of mixed sugar utilisation and biohydrogen synthesis based on genomic information.

Identification of functional genes associated with the biotransformation of limonene to trans-dihydrocarvone in Klebsiella sp. O852.

BACKGROUND: Natural dihydrocarvone has been widely used in the food, cosmetics, agrochemicals and pharmaceuticals industries because of its sensory properties and physiological effects. In our previous study, Klebsiella sp. O852 was shown to be capable of converting limonene to trans-dihydrocarvone with high catalytic efficiency. Thus, it was essential to identify and characterize the functional genes involved in limonene biotransformation using genome sequencing and heterologous expression. RESULTS: The 5.49-Mb draft genome sequence of Klebsiella sp. O852 contained 5218 protein-encoding genes. Seven candidate genes participating in the biotransformation of limonene to trans-dihydrocarvone were identified by genome analysis. Heterologous expression of these genes in Escherichia coli BL21(DE3) indicated that 0852_GM005124 and 0852_GM003417 could hydroxylate limonene in the six position to yield carveol, carvone and trans-dihydrocarvone. 0852_GM002332 and 0852_GM001602 could catalyze the oxidation of carveol to carvone and trans-dihydrocarvone. 0852_GM000709, 0852_GM001600 and 0852_GM000954 had high carvone reductase activity toward the hydrogenation of carvone to trans-dihydrocarvone. CONCLUSION: The results obtained in the present study suggest that the seven genes described above were responsible for converting limonene to trans-dihydrocarvone. The present study contributes to providing a foundation for the industrial production of trans-dihydrocarvone in microbial chassis cells using synthetic biology strategies. © 2021 Society of Chemical Industry.

Plant growth promoting activities and effect of fermented panchagavya isolate Klebsiella sp. PG-64 on Vigna radiata.

A natural bacterial isolate from fermented panchagavya named as PG-64, exhibits multiple plant growth-promoting traits. This Gram-negative bacteria was identified as Klebsiella sp. PG-64 by 16S rRNA gene sequencing. The Klebsiella sp. PG-64 has shown production of indole acetic acid (106.0 µg/ml), gibberellic acid (20.0 µg/ml), ammonia (7.12 µmol/ml), exopolysaccharide (2.04% w/v) and phosphate solubilization (106.0 µg/ml). It produced 437 µg/ml IAA with 0.75% (w/v) L-tryptophan supplementation and was increased to 575 µg/ml in a laboratory-scale fermenter. The PG-64 has shown tolerance to abiotic stress conditions like pH (5.0-12.0), temperature (28-46 °C), salt (0.5-10.0% w/v NaCl) and osmotic resistance (1-10% w/v PEG-6000). The PG-64 also produced 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (0.3 ng α-ketobutyrate/mg protein/h) indicating its potential for drought tolerance. Owing to its diverse properties, the effect of Klebsiella sp. PG-64 on Vigna radiata (Mung bean) was examined. The seeds treated with PG-64 culture showed 92% germination with a good seedling vigour index (202). In the pot study, Vigna radiata growth showed 2.23, 1.55, 2.00, 1.65, 1.73, 1.88, 5.00, 5.00, 1.57 times increase in primary root length, dry root weight, root hair numbers, leaf width, leaf numbers, leaf area, fruits number, flower number and chlorophyll content, respectively after 75 days. The application of Klebsiella sp. PG-64 culture resulted in substantial growth enhancement of Vigna radiata. The Klebsiella sp. PG-64 has multiple plant growth-promoting properties along with capabilities to tolerate abiotic stresses, making it a promising liquid biofertilizer contender for various crops.

Klebsiella sp.-related infectious spondylitis in a bearded dragon (Pogona vitticeps).

BACKGROUND: Spondylitis is an inflammation of the vertebrae that leads to a destructive process with exuberant new bone formation. Osteomyelitis can produce a distortion of the bone architecture, degenerative joint changes and ankyloses of adjacent vertebrae. In reptiles, intervertebral discs are absent, so the term discospondylitis is not used. In lizards, vertebral lesions have not been well studied. The present paper describes the first case of Klebsiella sp.-related spondylitis in a pet lizard (Pogona vitticeps). CASE PRESENTATION: A 2-year-old, female bearded dragon (Pogona vitticeps) was presented for clinical examination due to a decreased activity level, decreased appetite and constipation. Blood tests showed no remarkable alterations. The haemogram showed normal parameters with relative lymphocytosis, although the absolute number of lymphocytes did not differ from the reference values. A computed tomography scan revealed a mixed osteolytic-proliferative bone lesion diffusing to the first and last tracts of the pre-sacral vertebrae together. A small amount of material obtained from the spinal swelling was sampled with an aseptic technique for bacterial culture, which was positive for Klebsiella sp. The antibiogram revealed sensitivity to enrofloxacin, marbofloxacin, and chloramphenicol and intermediate sensitivity to gentamicin. Complete return to spontaneous feeding was achieved 15 days after the beginning of antibiotic and anti-inflammatory therapy. CONCLUSIONS: In veterinary medicine, spondylitis represents a well-known disease in small companion animals. In mammals, the most common aetiologic agents are fungi and bacteria. Antibiotic therapy was set based on the antibiogram, and marbofloxacin was chosen at a dosage of 10 mg/kg subcutaneously (SC) once per day (SID). After only 7 days of antibiotic therapy, the clinical condition improved significantly; the patient started feeding and drinking spontaneously and gained weight. This case should remind clinicians of the importance of always performing antibiograms before choosing any antibiotic therapy. Considering reptiles, there have been few papers about spinal diseases, mostly regarding snakes and a few about Iguana iguana. Relative to other species of saurians, the literature remains lacking.

Production, functional stability, and effect of rhamnolipid biosurfactant from Klebsiella sp. on phenanthrene degradation in various medium systems.

The present study investigated the stability and efficacy of a biosurfactant produced by Klebsiella sp. KOD36 under extreme conditions and its potential for enhancing the solubilization and degradation of phenanthrene in various environmental matrices. Klebsiella sp. KOD36 produced a mono-rhamnolipids biosurfactant with a low critical micelle concentration (CMC) value. The biosurfactant was stable under extreme conditions (60 °C, pH 10 and 10% salinity) and could lower surface tension by 30% and maintained an emulsification index of > 40%. The emulsion index was also higher (17-43%) in the presence of petroleum hydrocarbons compared to synthetic surfactant Triton X-100. Investigation on phenanthrene degradation in three different environmental matrices (aqueous, soil-slurry and soil) confirmed that the biosurfactant enhanced the solubilization and biodegradation of phenanthrene in all matrices. The high functional stability and performance of the biosurfactant under extreme conditions on phenanthrene degradation show the great potential of the biosurfactant for remediation applications under harsh environmental conditions.

Screening a Strain of Klebsiella sp. O852 and the Optimization of Fermentation Conditions for Trans-Dihydrocarvone Production.

Flavors and fragrances have high commercial value in the food, cosmetic, chemical and pharmaceutical industries. It is interesting to investigate the isolation and characterization of new microorganisms with the ability to produce flavor compounds. In this study, a new strain of Klebsiella sp. O852 (accession number CCTCC M2020509) was isolated from decayed navel orange (Citrus sinensis (L.) Osbeck), which was proved to be capable of converting limonene to trans-dihydrocarvone. Besides, the optimization of various reaction parameters to enhance the trans-dihydrocarvone production in shake flask was performed for Klebsiella sp. O852. The results showed that the yield of trans-dihydrocarvone reached up to 1 058 mg/L when Klebsiella sp. O852 was incubated using LB-M medium for 4 h at 36 °C and 150 rpm, and the biotransformation process was monitored for 36 h after adding 1680 mg/L limonene/ethanol (final ethanol concentration of 0.8% (v/v)). The content of trans-dihydrocarvone increased 16 times after optimization. This study provided a basis and reference for producing trans-dihydrocarvone by biotransformation.

Isolation and identification of naphthalene degrading bacteria and their degradation characteristics under rainwater environment in heavily polluted areas.

This study is screened for naphthalene degrading strains from a heavily polluted area with high naphthalene concentration in the rainwater for the effective removal of naphthalene from rainwater. Recently, naphthalene biodegradation has been achieved in water. However, the influences of organics and inorganics in the rainwater on the biodegradation of naphthalene remains unclear. The naphthalene degrading strain Klebsiella sp. (WJ-1) was identified from sewage sludge. The effects of temperature, pH, inoculum size, and rotation speed on the degradation ability of WJ-1 were studied. The results showed that the naphthalene degradation rates of WJ-1 in rainwater were higher than those in aqueous solution at different experimental conditions. The optimal conditions were 30 °C, 10% inoculum size, pH 7.0, and a rotation speed of 150 rpm. The substances in rainwater might be important co-metabolites of naphthalene degradation. Based on intermediate metabolites detected by gas chromatography-mass spectrometer (GC-MS), the naphthalene biodegradation pathway was identified, as being similar to the phthalic acid pathway. These results suggest WJ-1 as a good candidate for the efficient bioremediation of naphthalene from rainwater in heavily polluted areas.

Characterization of phenazine-1-carboxylic acid by Klebsiella sp. NP-C49 from the coral environment in Gulf of Kutch, India.

Coral-associated microbes from Marine National Park (MNP), Gulf of Kutch (GoK), Gujarat, India, were screened for siderophore production. Maximum siderophore-producing isolate NP-C49 and its compound were identified and characterized. The isolate was identified as Klebsiella sp. through 16S rRNA genes sequencing (GenBank accession nos. KY412519 and MTCC 25160). Antibiotic susceptibility profile against 20 commercial antibiotics showed its more sensitivity compared to human pathogenic strain, i.e., Klebsiella pneumonia. The compound was identified as phenazine-1-carboxylic acid (PCA) using the multinuclear ID (1H and 13C) and 2D (1H-1H COSY and 1H-13C HETCOR) NMR along with high-resolution mass spectrometry. No significant difference in the bacterial growth in the presence of PCA, FeCl3 and Fe(OH)3 indicated involvement of factors other than PCA in bacterial growth. The study first reports the identification and characterization of PCA from Klebsiella sp. both from terrestrial and marine sources.

Phylogenetic relationships, virulence and antimicrobial resistance properties of Klebsiella sp. isolated from pet turtles in Korea.

Klebsiella sp. are responsible for a multitude of infectious diseases in both humans and animals. In this study, phylogenetic relationships, virulence and antimicrobial resistance gene properties of 16 Klebsiella sp. isolated from 49 pet turtles were investigated. The isolates including Klebsiella oxytoca (n = 13) and Klebsiella pneumoniae (n = 3) were identified using 16S rRNA gene sequencing and each species formed distinct clusters in the neighbour-joining phylogenetic tree. The prevalence of virulence genes including ureC (100%) and kfu (68·75%) was observed among the isolates using Polymerase chain reaction (PCR) assay. The fimH, mrkD and rmpA genes were detected in all K. pneumoniae while these were absent in every K. oxytoca isolate. In antimicrobial susceptibility testing, high resistance rates were observed against ampicillin (100%) and cephalothin (62·50%). The resistance rates against imipenem, tetracycline, trimethoprim/sulfamethoxazole, nalidixic acid and ciprofloxacin were 12·50, 12·50, 12·50, 6·25 and 6·25% respectively. The presence of antimicrobial resistance genes such as plasmid-mediated quinolone resistance (PMQR) [qnrB (37·50%), qnrA (31·25%), qnrS (12·50%) and aac(6')-Ib-cr (12·50%)], extended-spectrum ß-lactamase (ESBL) [blaCTX-M (18·75%)], ß-lactamase [blaSHV-1 (18·75%)] and tetracycline resistance [tetE (12·50%)] was observed. The results revealed that pet turtle-borne Klebsiella sp. may carry different types of virulence and antimicrobial resistance genes which represents a potential threat to public health. SIGNIFICANCE AND IMPACT OF THE STUDY: Klebsiella sp. are nonmotile Gram-negative bacteria that are found in different environments. The virulence and antimicrobial resistance properties of pet turtle-borne Klebsiella sp. have not been studied before. Phylogenetic relationships, virulence traits and antimicrobial resistance profiles of pet turtle-borne Klebsiella sp. were characterized for the first time in Korea. Multiple virulence and antimicrobial resistance genes were observed among the isolates. The occurrence of virulence and antimicrobial resistance determinants in Klebsiella sp. may represent a potential threat to public health.

Prevalence of Multi-Antibiotic Resistant Escherichia coli and Klebsiella species obtained from a Tertiary Medical Institution in Oyo State, Nigeria.

Background: The development of multi-antibiotic resistant bacteria, especially Gram-negative bacteria which are the major cause of hospital-acquired infections worldwide, had been increasing. Escherichia coli and Klebsiella sp. had become more resistant to different classes of antibiotics, and the treatment of infections caused by these bacteria had developed into a challenge in both developed and developing countries. This study had determined the multi-antibiotic resistance (MAR) patterns of Escherichia coli and Klebsiella sp. isolated from clinical inpatient and outpatient samples. Method: The present study had used 50 E. coli and 48 Klebsiella sp. isolates. Antibiotic susceptibility test had been carried out by using disk diffusion method, and the interpretation of results of the zones of inhibition had accorded with Clinical Laboratory Standards Institute (CLSI). The antibiotics used had included the following: streptomycin, ciprofloxacin, erythromycin, nitrofurantoin, amikacin, gentamicin, ofloxacin, cefepime, oxacillin, colistin sulfate, cefotaxime, ceftazidime, pefloxacine, and cloxacillin. Results: E. coli and K. pneumoniae had shown high-resistance patterns. E. coli had exhibited high resistance against cloxacillin (96%), oxacillin (96%), erythromycin (88%), and most especially streptomycin (98%). Similarly, K. pneumoniae had presented a high resistance to streptomycin (88%), cloxacillin (92%), oxacillin (92%), and colistin (92%). E. coli had presented the highest multidrug resistance with a MAR index of 1.00. A total of 17 E. coli isolates had shown resistance to the 14 antibiotics tested. Conclusion: E. coli and Klebsiella sp. in clinical isolates in outpatients and inpatients in Ibadan, Western Nigeria had demonstrated high antimicrobial resistance. Thus, such condition should be considered a major public health concern, and measures must be taken to establish the sources and drivers of this problem.

Cloning of a novel gene involved in alkane biosynthesis from Klebsiella sp.

Aliphatic medium-chain alkanes, a major component of gasoline, diesel, and jet fuels, are drop-in compatible fuels. Microorganisms with the capacity to produce medium-chain alkanes are promising for the bio-production of drop-in fuel. We found that Klebsiella sp. NBRC100048 has the ability to produce medium-chain alkanes from medium-chain aldehydes. We cloned a gene involved in conversion of aldehydes to alkanes by using a genomic fosmid library derived from Klebsiella sp. NBRC100048. The gene termed orf2991 encodes 506 amino acids and shows 62% sequence homology to the aldehyde dehydrogenase of Escherichia coli, aldB. The finding of orf2991 as a novel alkane-synthesizing enzyme gene similar to E. coli aldehyde dehydrogenase family, which is generally known to catalyze a reaction oxidizing aldehydes to fatty acids, indicated a novel function of aldehyde dehydrogenase. This finding is not only significant academically but allows developing the novel manufacturing methods of alkanes fermentation.

Aflatoxin B1 removal by three bacterial strains and optimization of fermentation process parameters.

Aflatoxin B1 (AFB1 ) removing bacterial strains were isolated from different habitats that were easily contaminated by AFB1 . Furthermore, the composition of the fermentation medium and conditions of fermentation process were optimized, including carbon source, nitrogen source, metal ions, temperature, initial pH value, inoculation volume, and culture broth volume. Using coumarin as the sole carbon and energy source, we primarily screened 31 strains, and 10 strains were found to be capable to remove AFB1 . Among them, the highest removal rate of 71.91% appeared in those isolated from rotten wood (poplar). Strains XY1, XY3, and T6 were carried out to identify, and the results were Klebsiella sp., Klebsiella pneumonia, and Pantoea sp., respectively. Corn cob powder and tryptone can significantly increase the AFB1 removal activity of these strains. The AFB1 removal activity of Klebsiella sp.XY1 and K. pneumonia XY3 can be enhanced by Ca2+ , and those of Pantoea sp. T6 can be enhanced by Cu2+ . Temperature and initial pH were positively correlated with the AFB1 removal activity of these strains in a certain range. This study not only provides reference for the screening and application of AFB1 removing bacteria, but also provides a basis for possible application in the food and feed industry.

Biohydrogen production from fermentation of cotton stalk hydrolysate by Klebsiella sp. WL1316 newly isolated from wild carp (Cyprinus carpio L.) of the Tarim River basin.

A new hydrogen-producing bacterium was isolated from the intestine of wild carp (Cyprinus carpio L.) of the Tarim River Basin. The isolate was identified as Klebsiella sp. based on 16S rDNA gene sequencing and examination of physiological and biochemical characteristics. The isolated strain, Klebsiella sp. WL1316, could effectively produce a high yield of hydrogen by using cotton stalk hydrolysate as substrate. The optimum fermentation conditions for hydrogen production were determined as follows: an initial sugar concentration of 40 g/L, a fermentation temperature of 37 °C and an initial pH value of 8.0. The scaled-up fermentation process was conducted in a 5-L fermenter using these parameters. Higher productivities with maximum daily hydrogen production of 937.0 ± 41.0 mL L-1 day-1, cumulative hydrogen production of 2908.5 ± 47.4 mL L-1, viable cell count of (20.2 ± 0.6) × 108 CFU mL-1 and hydrogen yield of 1.44 ± 0.08 mol mol-1sugarconsumed were obtained. The cumulative hydrogen production was predicted by the modified Gompertz equation with R 2 of 0.997, and values of R m and P were 44.8 mL L-1 h-1 and 3057.6 mL L-1, respectively. These results indicated that the strain Klebsiella sp. WL1316 resulted in a high hydrogen production rate (HPR) and good hydrogen production potential. Moreover, this strain exhibited higher values of maximum hydrogen yield and HPR than the reported pure cultures.

Mining alfalfa (Medicago sativa L.) nodules for salinity tolerant non-rhizobial bacteria to improve growth of alfalfa under salinity stress.

There are fewer reports on plant growth promoting (PGP) bacteria living in nodules as helper to tolerance to abiotic stress such as salinity and drought. The study was conducted to isolate rhizobial and non-rhizobial drought and salinity tolerant bacteria from the surface sterilized root nodules of alfalfa, grown in saline soils, and evaluate the effects of effective isolates on plant growth under salt stress. Based on drought and salinity tolerance of bacterial isolates and having multiple PGP traits, two non-rhizobial endophytic isolates and one rhizobial endophytic isolate were selected for further identification and characterization. Based on partial sequences of 16 S rRNA genes, non-rhizobial isolates and rhizobial isolate were closely related to Klebsiella sp., Kosakonia cowanii, and Sinorhizobium meliloti, respectively. None of the two non-rhizobial strains were able to form nodules on alfalfa roots under greenhouse and in vitro conditions. Co-inoculation of alfalfa plant with Klebsiella sp. A36, K. cowanii A37, and rhizobial strain S. meliloti ARh29 had a positive effect on plant growth indices under salinity stress. In addition, the single inoculation of non-rhizobial strains without rhizobial strain resulted in an increase in alfalfa growth indices compared to the plants non-inoculated and the ones inoculated with S. meliloti ARh29 alone under salinity stress, indicating that nodule non-rhizobial strains have PGP potentials and may be a promising way for improving effectiveness of Rhizobium bio-fertilizers in salt-affected soils.

Biohydrogen Production by Antarctic Psychrotolerant Klebsiella sp. ABZ11.

Lower temperature biohydrogen production has always been attractive, due to the lower energy requirements. However, the slow metabolic rate of psychrotolerant biohydrogen-producing bacteria is a common problem that affects their biohydrogen yield. This study reports on the improved substrate synthesis and biohydrogen productivity by the psychrotolerant Klebsiella sp. strain ABZ11, isolated from Antarctic seawater sample. The isolate was screened for biohydrogen production at 30°C, under facultative anaerobic condition. The isolate is able to ferment glucose, fructose and sucrose with biohydrogen production rate and yield of 0.8 mol/l/h and 3.8 mol/g, respectively at 10 g/l glucose concentration. It also showed 74% carbohydrate uptake and 95% oxygen uptake ability, and a wide growth temperature range with optimum at 37°C. Klebsiella sp. ABZ11 has a short biohydrogen production lag phase, fast substrate uptake and is able to tolerate the presence of oxygen in the culture medium. Thus, the isolate has a potential to be used for lower temperature biohydrogen production process.

Enhancement of electricity production in a mediatorless air-cathode microbial fuel cell using Klebsiella sp. IR21.

A novel dissimilatory iron-reducing bacteria, Klebsiella sp. IR21, was isolated from the anode biofilm of an MFC reactor. Klebsiella sp. IR21 reduced 27.8 % of ferric iron to ferrous iron demonstrating that Klebsiella sp. IR21 has electron transfer ability. Additionally, Klebsiella sp. IR21 generated electricity forming a biofilm on the anode surface. When a pure culture of Klebsiella sp. IR21 was supplied into a single chamber, air-cathode MFC fed with a mixture of glucose and acetate (500 mg L(-1) COD), 40-60 mV of voltage (17-26 mA m(-2) of current density) was produced. Klebsiella sp. IR21 was also utilized as a biocatalyst to improve the electrical performance of a conventional MFC reactor. A single chamber, air-cathode MFC was fed with reject wastewater (10,000 mg L(-1) COD) from a H2 fermentation reactor. The average voltage, current density, and power density were 142.9 ± 25.74 mV, 60.5 ± 11.61 mA m(-2), and 8.9 ± 3.65 mW m(-2), respectively, in the MFC without inoculation of Klebsiella sp. IR21. However, these electrical performances of the MFC were significantly increased to 204.7 ± 40.24 mV, 87.5 ± 17.20 mA m(-2), and 18.6 ± 7.23 mW m(-2), respectively, with inoculation of Klebsiella sp. IR21. The results indicate that Klebsiella sp. IR21 can be utilized as a biocatalyst for enhancement of electrical performance in MFC systems.

Optimized production of a novel bioflocculant M-C11 by Klebsiella sp. and its application in sludge dewatering.

The optimized production of a novel bioflocculant M-C11 produced by Klebsiella sp. and its application in sludge dewatering were investigated. The optimal medium carbon source, nitrogen source, metal ion, initial pH and culture temperature for the bioflocculant production were glucose, NaNO3, MgSO4, and pH7.0 and 25°C, respectively. A compositional analysis indicated that the purified M-C11 consisted of 91.2% sugar, 4.6% protein and 3.9% nucleic acids (m/m). A Fourier transform infrared spectrum confirmed the presence of carboxyl, hydroxyl, methoxyl and amino groups. The microbial flocculant exhibited excellent pH and thermal stability in a kaolin suspension over a pH range of 4.0 to 8.0 and a temperature range of 20 to 60°C. The optimum bioflocculating activity was observed as 92.37% for 2.56mL M-C11 and 0.37g/L CaCl2 dosages using response surface methodology. The sludge resistance in filtration (SRF) decreased from 11.6×10(12) to 4.7×10(12)m/kg, which indicated that the sludge dewaterability was remarkably enhanced by the bioflocculant conditioning. The sludge dewatering performance conditioned by M-C11 was more efficient than that of inorganic flocculating reagents, such as aluminum sulfate and polymeric aluminum chloride. The bioflocculant has advantages over traditional sludge conditioners due to its lower cost, benign biodegradability and negligible secondary pollution. In addition, the bioflocculant was favorably adapted to the specific sludge pH and salinity.

Decolourization of azo dyes by a newly isolated Klebsiella sp. strain Y3, and effects of various factors on biodegradation.

In this study, we isolated and characterized a new strain of Klebsiella sp. Y3, which was capable of decolourizing azo dyes under anaerobic conditions. The effects of physico-chemical parameters on the Methyl Red degradation by the strain were determined. The results indicated that strain Y3 exhibited a good decolourization ability in the range of pH from 4 to 9, temperature from 30 °C to 42 °C and salinity from 1% to 4%. A broad spectrum of azo dyes with different structures could be decolourized by the strain. The isolate decolourized Methyl Red, Congo Red, Orange I and Methyl Orange by almost 100% (100 mg/L) in 48 h. The culture exhibited an ability to decolourize repeated additions of dye, showing that the strain could be used for multiple cycles of biodegradation. Azo dyes at high concentrations could be tolerated and degraded by Y3. An almost complete mineralization of Methyl Red and Congo Red at the concentration of 800 mg/L was observed within 48 h. The high degradation potential of this bacterium supports its use in the treatment of industrial wastewater containing azo dyes.

Isolation and Electrochemical Analysis of a Facultative Anaerobic Electrogenic Strain Klebsiella sp. SQ-1.

Electricigens decompose organic matter and convert stored chemical energy into electrical energy through extracellular electron transfer. They are significant biocatalysts for microbial fuel cells with practical applications in green energy generation, effluent treatment, and bioremediation. A facultative anaerobic electrogenic strain SQ-1 is isolated from sludge in a biotechnology factory. The strain SQ-1 is a close relative of Klebsiella variicola. Multilayered biofilms form on the surface of a carbon electrode after the isolated bacteria are inoculated into a microbial fuel cell device. This strain produces high current densities of 625 µA cm-2 by using acetate as the carbon source in a three-electrode configuration. The electricity generation performance is also analyzed in a dual-chamber microbial fuel cell. It reaches a maximum power density of 560 mW m-2 when the corresponding output voltage is 0.59 V. The facultative strain SQ-1 utilizes hydrous ferric oxide as an electron acceptor to perform extracellular electricigenic respiration in anaerobic conditions. Since facultative strains possess better properties than anaerobic strains, Klebsiella sp. SQ-1 may be a promising exoelectrogenic strain for applications in microbial electrochemistry.