• Toxicological Research
• /
• v.23 no.4
• /
• pp.373-382
• /
• 2007

This study was conducted to obtain acute information of the oral dose toxicity of PGB-1, a novel polyglucosamine polymer produced from a new strain Enterobacter sp. BL-2 in male and female mice. In order to calculated 50% lethal dose ($LD_{50}$) and approximate lethal dose (LD), test material was once orally administered to male and female ICR mice at dose levels of 2000, 1000, 500, 250, 125 and 0 (vehicle control) ml/kg (body wt.). The mortality and changes on body weight, clinical signs, gross observation and organ weight and histopathology of principle organs were monitored 14 days after dosing with PGB-1. We could not find any mortalities, clinical signs, body weight changes and gross findings. In addition, significant changes in the organ weight and histopathology of principal organs were not observed except for some sporadic findings. The results obtained in this study suggest that PGB-1 may not be toxic in mice and may be therefore safe for clinical use. The $LD_{50}$ and approximate LD in mice after single oral dose of PGB-1 were considered over 2000 mg/kg in both female and male mice.

• Asian-Australasian Journal of Animal Sciences
• /
• v.26 no.9
• /
• pp.1304-1312
• /
• 2013

The effects of storage period and aerobic deterioration on the bacterial community were examined in Italian ryegrass (IR), guinea grass (GG), and whole-crop maize (WM) silages. Direct-cut forages were stored in a laboratory silo for 3, 7, 14, 28, 56, and 120 d without any additives; live counts, content of fermentation products, and characteristics of the bacterial community were determined. 2,3-Butanediol, acetic acid, and lactic acid were the dominant fermentation products in the IR, GG, and WM silages, respectively. The acetic acid content increased as a result of prolonged ensiling, regardless of the type of silage crop, and the changes were distinctively visible from the beginning of GG ensiling. Pantoea agglomerans, Rahnella aquatilis, and Enterobacter sp. were the major bacteria in the IR silage, indicating that alcoholic fermentation may be due to the activity of enterobacteria. Staphylococcus sciuri and Bacillus pumilus were detected when IR silage was spoiled, whereas between aerobically stable and unstable silages, no differences were seen in the bacterial community at silo opening. Lactococcus lactis was a representative bacterium, although acetic acid was the major fermentation product in the GG silage. Lactobacillus plantarum, Lactobacillus brevis, and Morganella morganii were suggested to be associated with the increase in acetic acid due to prolonged storage. Enterobacter cloacae appeared when the GG silage was spoiled. In the WM silage, no distinctive changes due to prolonged ensiling were seen in the bacterial community. Throughout the ensiling, Weissella paramesenteroides, Weissella confusa, and Klebsiella pneumoniae were present in addition to L. plantarum, L. brevis, and L. lactis. Upon deterioration, Acetobacter pasteurianus, Klebsiella variicola, Enterobacter hormaechei, and Bacillus gibsonii were detected. These results demonstrate the diverse bacterial community that evolves during ensiling and aerobic spoilage of IR, GG, and WM silages.

• Journal of Food Hygiene and Safety
• /
• v.24 no.4
• /
• pp.307-311
• /
• 2009

The objectives of this study were to compare the biochemical profiles with biogroups for the identification of Cronobacter spp. (formally known as Enterobacter sakazakii) isolates using biochemical identification kits. A total of 38 Cronobacter spp. contained 5 clinical, 31 food, and 2 environmental isolates were used. All isolates were identified as Cronobacter spp. with the Vitek II system and ID 32E kit. The API 20E kit identified all isolates as Cronobacter spp. but the percentage identification was 51.1% for 16 of 38 isolates. These strains were contained to Biogroup 2, 9, 10, and 11. The utilization of inositol is a factor determining the percentage identification of Cronobacter spp. with the API 20E kit.

• Food Science and Biotechnology
• /
• v.16 no.6
• /
• pp.948-953
• /
• 2007

The powdered cereal sunsik is a partially thermal-processed product that required safety evaluations for food-borne pathogens. Thirty-six sunsik products from Korean markets were collected and analyzed for contamination by total viable cell counts, coliforms, Escherichia coli, and the spore-forming Clostridium perfringens and Bacillus cereus. Enterobacter sakazakii, as a newly emerging pathogen, was also analyzed. Approximately 28% of sunsik were contaminated at 5 log CFU/g for total viable counts. Coliforms and E. coli were detected in 33 and 4% of the samples, respectively. The spore-forming B. cereus was found in 42% of the samples at a maximal level of 3 log CFU/g on average. About 6% the samples were contaminated with Cl. perfringens at an average level of 15 CFU/g. Forty-five % of sunsik contained E. sakazakii, at levels from 0.007 to over 1.1 cell/g by MPN method. In addition, one sunsik product for infants and children showed over 3 log CFU/g for both B. cereus and E. sakazaki. Therefore, concern should be placed on controlling for microbial hazards such as B. cereus and E. sakazakii in sunsik, particularly for the products fed to infants under 6 months of age.

• Food Science and Biotechnology
• /
• v.18 no.6
• /
• pp.1537-1540
• /
• 2009

Enterobacter sakazakii is a representative microorganism whose presence in infant foods can cause serious disease. The purposes of this study were to determine the inactivation effects of intense pulsed light (IPL) on E. sakazakii and the commercial feasibility of this sterilization method. The inactivation of E. sakazakii increased with increasing electric power and treatment time. The cells were reduced by 5 log cycles for 4.6 and 1.8 msec of treatment at 10 and 15 kV of electric field strength, respectively. The sterilization effects on commercial infant foods were investigated at 15 kV. The cell population in an infant beverage, an infant meal, and an infant powdered milk product inoculated with E. sakazakii were inactivated exponentially as a function of time and reduced by 4.0, 2.5, and 1.5 log cycles for 9.4, 7.0, and 7.0 msec of treatment time, respectively.

• Journal of Dairy Science and Biotechnology
• /
• v.23 no.1
• /
• pp.65-71
• /
• 2005

Powered infant formula and baby food contaminated with Enterobacter sakazakii were reported to cause infection among infants and to be associated with sporadic cases and outbreaks of sepsis, menigitis, cerebritis, and necrotizing enterocolitis. Salmonella contamination of infant formula has also been responsible for multiple outbreaks. Other species of Enterobacteriaceae in powdered infant formula may be causative agents, about which there has been no report. Other pathogenic bacteria have been isolated from powdered infant formula but they were not associated with outbreaks among infant. While Enterobacter sakazakii caused disease in all age groups, premature infants under 28 days old and with birth weight are most sensitive to its infection. Even if low contamination level of the bacteria in powdered infant formula and baby food may not cause infection, the possibility to multiplicate during preparation and storage of reconstituted formula may increase. The etiological factors and pathogenecity of S. sakazakii have not been elucidated. There were wide variability in phenotype and genotype between its strains. S. sakazakii has been isolated from factory facility and surroundings more frequently than Salmonella and thus factory environment should be the source for post-processing contamination of the formula with S. sakazakii. Considering current technology to manufacture power infant formula and baby food it is impossible to sterilize powdered formula but the frequency of outbreak hazard by S. sakazakii can be reduced by pasteurizing the formula base before drying and shortening storage time of the reconstituted formula.

• Microbiology and Biotechnology Letters
• /
• v.16 no.5
• /
• pp.352-357
• /
• 1988

Twenty-five out of 35 strains isolated from fermented corn meal produced folic acid. Bacillus licheniformis strain 6 and Enterobacter cloacae strain 18 produced the largest quantities of 1830$\pm$271 ng and 1350$\pm$161 ng per 100$m\ell$ of the assay broth, respectively. B. licheniformis produced maximum yields when initial pH values were 6,7, or 8 and were incubated at 35$^{\circ}C$ for 5 days. The initial pH (range 4-8) had no effect on folic acid production by E. cloacae； 55 $^{\circ}C$ for 5 days was optimal for this bacterium. Added carbohydrates had no effect on the production of total folic acid in the bacterial cells in pure or mixed cultures. However, in their growth media, carbohydrates enhanced the production of free and total folic acid by E. cloacae and in the mixed cultures. Added carbohydrates had no significant (P < 0.05) effect on the production of free and total folic acid by B. licheniformis.

• Microbiology and Biotechnology Letters
• /
• v.16 no.2
• /
• pp.98-104
• /
• 1988

A bacterial isolate FRI-33 which produces hydrophillic polysaccharide was identified and its cultural condition was investigated. FRI-33 was identified as Enterobacter agglomerans. The optimum cultural conditions for polysaccharide production were 3$0^{\circ}C$, pH 5.7, using medium composed of glucose 25 g/$\ell$, peptone 2.0 g/$\ell$, yeast extract 0.5 g/$\ell$, KH$_2$PO$_4$ 1.0g/$\ell$, MgSO$_4$.7H$_2$ O 1.0g/$\ell$, CaCO$_3$ 2.5g/$\ell$. The polysaccharide production after 72 hours was 8.41 g/$\ell$. The polysaccharide was composed of galactose (1.0 mole), xylose (1.5 mole), gluconodeltalactone (1.9 mole) and ribose (0.03 mole). The apparent viscosity of 1% polysaccharide solution was 504 mPa.s at 60 rpm and intrinsic viscosity was 45.80 d$\ell$/ g.

• Journal of Microbiology and Biotechnology
• /
• v.28 no.6
• /
• pp.968-975
• /
• 2018

In the course of screening for microbes with nematicidal activity, we found that Enterobacter asburiae HK169 displayed promising nematicidal activity against the root-knot nematode Meloidogyne incognita, along with plant growth-promoting properties. Soil drenching of a culture of HK169 reduced gall formation by 66% while also increasing root and shoot weights by 251% and 160%, respectively, compared with an untreated control. The cell-free culture filtrate of the HK169 culture killed all juveniles of M. incognita within 48 h. In addition, the nematicidal activity of the culture filtrate was dramatically reduced by a protease inhibitor, suggesting that proteolytic enzymes contribute to the nematicidal activity of HK169. In order to obtain genomic information about the HK169 isolate related to its nematicidal and plant growth-promoting activities, we sequenced and analyzed the whole genome of the HK169 isolate, and the resulting information provided evidence that the HK169 isolate has nematicidal and plant growth-promoting activities. Taken together, these observations enable the future application of E. asburiae HK169 as a biocontrol agent for nematode control and promote our understanding of the beneficial interactions between E. asburiae HK169 and plants.

• Korean Journal of Agricultural Science
• /
• v.43 no.3
• /
• pp.401-414
• /
• 2016

The synergistic effect on phosphate solubilization of single- and co-inoculation of two phosphate solubilizing bacteria, Burkholderia anthina PSB-15 and Enterobacter aerogenes PSB-16, was assessed in liquid medium and green gram plants. Co-inoculation of two strains was found to release the highest content of soluble phosphorus ($519{\mu}g\;mL^{-1}$) into the medium, followed by single inoculation of Burkholderia strain ($492{\mu}g\;mL^{-1}$) and Enterobacter strain ($483{\mu}g\;mL^{-1}$). However, there was no significant difference between single inoculation of bacterial strain and co-inoculation of two bacterial strains in terms of phosphorous release. The highest pH reduction, organic acid production, and glucose consumption were observed in the culture medium co-inoculated with PSB-15 and PSB-16 strains rather than that of single inoculation. Based on the plant growth promotion bioassay, co-inoculated mung bean seedlings recorded 9% and 8% higher shoot and root growth, respectively, compared to the control. Therefore, in conclusion, co-inoculation of the strains B. anthina and E. aerogenes displayed better performance in stimulating plant growth than inoculation of each strain alone. However, considering the short assessment period of the present study, we recommend engaging in further work under field conditions in order to test the suitability of these strains as bio-inoculants.