Neosartorya and Talaromyces are typical fungi capable of producing heat resistant ascospores responsible for the spoilage of processed fruit products. In this study, the heat activation rates of Neosartorya and Talaromyces ascospores were investigated in several suspending media at various heating temperatures. Ascospores were dispersed in pH 3.5 McIlvain buffer, organic acid/alcohol-supplemented McIlvain buffer and grape juice (pH 3.5, 5.0°Brix) prior to heat treatments. In McIlvain buffer, the number of germinating ascospores increased logarithmically with longer exposure to heating at all test temperatures. Heat activation rates (k values) accelerated with increasing temperature. The calculated activation energy (Ea) values were similar among ascospores from the same genus, but the Ea of the test Neosartorya spp. were greater than that of the test Talaromyces spp. Greater k values were calculated from acetate-supplemented McIlvain buffer and grape juice. Similarly, normal- and branched-chain fatty acids were shown to enhance the heat activation rate of the ascospores in McIlvain buffer systems. These results could assist the food industry in designing adequate thermal processes for food products against the heat resistant fungi.
An Alcanivorax dieselolei strain, termed strain N1203, was isolated from the consortia of ammonia-oxidizing bacteria (AOB) combined with denitrifying bacteria from our previous study and was shown to have ability to reduce nitrate to nitrite to either nitrous oxide or molecular nitrogen. Analysis of 16S rRNA gene sequences established strain N1203 as a member of the species Alcanivorax dieselolei. In addition, the ability of strain N1203 to utilize various organic substrates as the sole carbon source, supplemented with carbohydrates, amino acids, and n-alkane compounds, was investigated, and this strain was found to have a narrow substrate range of growth such as grycerol, succinate, ethanol and n-alkane hydrocarbon. Furthermore, N1203's stepwise denitrifying activity, utilizing succinate and hexadecane as sole carbon sources, was measured. Gene fragments of nirK and qnorB genes, which are involved in denitrifying activities, were obtained, cloned and sequenced. Phylogenetic analysis for these two genes showed that both the nirK and qnorB sequences, although found in separate branches within clusters, formed subclusters branching from uncultured environmental clones. This demonstrated the typical uniqueness of these genes from any cultivated denitrifiers. Thus, strain N1203 is novel type of denitrifying bacteria that demonstrated denitrifying activities when cultivated using succinate as the sole carbon source.
Proanthocyanidin, which consists of (+) catechin, (-) epicatechin and their gallates (15%), (-) epicatechin gallate-dimers, -trimers, and -tetramers (80%), and (-) epicatechin gallate-pentamers, -hexamers, and -heptamers (5%), was evaluated for its antiviral activity against feline calicivirus F9 strain (FCV/F9), which is thought to be a surrogate for noroviruses, and coxsackievirus A7 strain (Cox.A7), which was selected as a representative enteric virus. To achieve a viral inactivation rate of 99% or greater after contact for 10 sec., at least 1 mg/ml and 10 mg/ml of proanthocyanidin were required against FCV/F9 and Cox.A7, respectively. Although the antiviral mechanism of proanthocyanidin is not clear at present, proanthocyanidin may be an effective disinfectant against enteroviruses such as noroviruses.
Bactericidal and sporicidal activities of an improved iodide formulation (tentatively designated as the distilled KMT reagent: pH around 3) and its derivative (tentatively designated as the distilled ethanol reagent: pH around 2.5) were examined in several dilutions against vegetative bacteria and Bacillus subtilis spores, and they were compared with two kinds of intermediate-level disinfectants, i.e., 7% povidone-iodine (ISODINE®) and ethanol for disinfection (76.9∼81.4 vol%). Each solution of distilled KMT reagent up to a dilution of 1:100 showed potent bactericidal activity against most tested bacteria when used for 30 seconds at 20°C. Bactericidal activities at these dilutions were almost comparable with those of the same dilution of ISODINE®. Although the 1:10 dilution of ISODINE® did not show comparable sporicidal activity, the same dilution of distilled KMT reagent showed potent sporicidal activity. On the other hand, the 1:2 dilution of distilled ethanol reagent showed potent sporicidal activity when used for 5 minutes at 60°C. Ethanol for disinfection did not show any sporicidal activity even with treatment for 60 minutes at 60°C. With treatment for 30 sec at 37°C, the 1:2 dilution of distilled ethanol reagent was found to have effective bactericidal activity almost comparable with that of ethanol for disinfection. Appropriate dilutions of both the distilled KMT reagent and distilled ethanol reagent may be applicable as antiseptics which are able to achieve high-level disinfection.
One psychrophilic yeast strain, that grew well in a cold environment such as in a refrigerator, was isolated from the yeast starter (Loog-pang) of a traditional alcohol drink in Thailand. The isolated strain OPU-FC11 was identified as Cryptococcus diffluens by the assay for 26S ribosomal DNA and the test for carbon source assimilation. OPU-FC11 showed a good amount of growth at 4°C at which a commonly found yeast like Saccharomyces cerevisiae did not grow, and produced cold-adapted enzymes that showed a relatively high activity at lower temperatures.
The purpose of this study was to evaluate the most-probable-number dilution plate (MPN plate) method developed for the enumeration of Escherichia coli in water samples. Sterilized water was inoculated with E. coli ATCC 11775 to give between 2-1600 MPN/100ml. The MPN was determined for both the MPN plate and 5-tube methods from the MPN table. The average of the natural logarithm (ln) MPN with standard deviations in 95 samples was 4.26 +/- 1.48 by the 5-tube-method and 4.18 +/- 1.45 by the MPN plate method. The correlation coefficient was 0.96. These results were not significantly different according to the paired t-test (p>0.05).
In this study, we developed a predictive program for Vibrio parahaemolyticus growth under various environmental conditions. Raw growth data was obtained with a V. parahaemolyticus O3:K6 strain cultured at a variety of broth temperatures, pH, and salt concentrations. Data were analyzed with our logistic model and the parameter values of the model were analyzed with polynomial equations. A prediction program consisting of the growth model and the polynomial equations was then developed. After the range of the growth environments was modified, the program successfully predicted the growth for all environments tested. The program could be a useful tool to ensure the bacteriological safety of seafood.
The sidewall modified single-walled carbon nanotubes (SWNTs) with amino-containing substituents were prepared using the radicals generated by the photolysis of acetonitrile. A subsequent treatment of modified SWNTs with the Ag colloid gave an attachment of Ag nanoparticles on the surface of SWNTs through the functionalized linkages. The Ag nanoparticle-modified SWNTs evaluated by antibacterial tests showed strong activities against Escherichia coli and Staphylococcus aureus. However, the use of Ag nanoparticle-modified SWNTs on simulated body fluid exhibited weaker antibacterial activity.