Scallop shells subjected to heat treatment exhibit antimicrobial activity, and heated scallop-shell powder (HSSP) has recently been reported to be effective for disinfecting food. However, because the main component of these shells is calcium oxide, there is a problem that scales of calcium carbonate (CaCO3) become established on the surface of equipment used for food processing. In this study, we thus investigated whether the addition of sugar to HSSP slurry suppressed CaCO3 scale generation and whether the sugar-supplemented HSSP could be applied to the disinfection and preservation of fresh lettuce. The results showed that glucose, sucrose, and sorbitol could suppress the scale generation in HSSP slurry. However, glucose and sucrose decreased the antibacterial activity of HSSP. Since the addition of sorbitol did not affect the antibacterial activity of HSSP slurry, it was used for subsequent experiments because of its low bioavailability. Sorbitol effectively suppressed scale formation by dissolving it before the addition of HSSP. The disinfection and preservative effects of sorbitol-supplemented HSSP ( S-HSSP) treatment on lettuce did not decrease compared with those upon HSSP treatment and were almost equal to or higher than those of sodium hypochlorite treatment at 200 mg/l. The addition of sorbitol solved the major problem of scale generation by HSSP containing CaO, which contributes to expansion of usage of heated shell powder, such as HSSP, in food processing.
In this study, the relationship between plasma gas temperature and the bactericidal effects on five of bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecalis and Bacillus cereus (spore)) in liquid was investigated using a temperature-controllable plasma source. We determined that the bactericidal ability improved as the plasma gas temperature increased. Specifically, the bactericidal ability on E. coli of 80-℃ plasma was enhanced by as much as 6.3 times compared to that of 10-℃ plasma. The relationship between plasma gas temperature and the amount of hydroxyl radical, singlet oxygen, hydrogen peroxide, and ozone introduced into the solution was investigated. Our results also showed that each reactive species production increased by 2.1, 9.0, 1.6, and 17 times, respectively, with 80-℃ compared to 10-℃ plasma. The relationship between the bactericidal ability and amount of reactive species indicated that singlet oxygen and ozone introduced to the solution mostly influenced the bactericidal ability as the plasma gas temperature increased. We conclude that the plasma gas temperature is the crucial parameter for plasma sterilization.
In storage of modern museums, collections are packed and stored with acid-free paper-based materials for keeping safe and stable conditions. Direct contact of fungal contaminated packing and storing materials with the collections is concerned about expanding of infection in storage facilities. In this study, fungicidal effects of UV light irradiation on the materials such as archival board and Japanese tissue paper contaminated with Penicilliun commune and Chaetomium globosum were tested. The analyzed materials were divided into two groups; Group 1 was examined with 20 μl of spore suspensions of fungi (106 cfu/ml) ; and Group 2 was tested on Czapek- Dox agar medium modified without sugar and inoculated with 100 μl of the spore suspensions of fungi (106 cfu/ml) . Six doses of UV irradiation were examined on Group 1 and five doses on Group 2 in addition to control. The assessment was done by using 1) adenosine triphosphate (ATP) bioluminescence assay and double staining to determine the cell viability; 2) observation under light microscope to evaluate morphophysiological change of tested fungi (spores and hyphae) . Because of the thinness and high transparency of tissue paper, UV irradiations were highly efficient to fungicide its fungal contamination compared with archival board. In spite of the high resistance of C. globosum spores, the rate of growth was slow, and with a little amount of perithecia or fruiting bodies and a high amount of ycelium (which damaged rapidly through UV irradiation) . This may be due to a low relative humidity of the incubation environment. Minimum dosage of UV irradiation with fungicidal effectiveness against all fungal contamination was estimated as 118 J/cm2.
The molecular, morphological, and physiological characters of 55 Ochroconis strains collected from indoor and outdoor environments were studied. In Japan, Ochroconis species are often found in indoor detergent-rich environments, such as bathrooms and washing machines, and the predominant species have been identified as O. humicola, similar to that in other Asian and European countries. Although Ochroconis species have rarely been found in outdoor environments such as mountains, forests, and agricultural fields, in the present study, Ochroconis strains were specifically isolated from the soils of urban city parks. Phylogenetic analysis conducted using the 28S ribosomal RNA (28S rDNA) gene sequence showed that almost all of the Ochroconis strains found in indoor environments (i.e., water supply) were O. humicola. Although city parks were often surrounded by residences, more than half of the Ochroconis strains collected from the soils of city parks examined in this study were different Ochroconis species. The ability to use detergents as nutrients was found in a new genetic group (probably a new species) isolated from the soils of city parks as well as in O. humicola and O. constricta. Ochroconis humicola is assumed to adapt mostly to indoor environments and to penetrate from the outdoors, e.g., soils of urban areas. To elucidate the factors promoting indoor fungal predominance, the ability of using surfactants as nutrients was compared among these three species. Additionally, growth under alkaline and drought conditions, and heat tolerance were examined. Indoor predominance of O. humicola compared to that of the other two species was attributed to the ability of using a non-ionic surfactant as nutrient and to growth under alkaline conditions.
Viability of chlorine-injured E. coli O157:H7 inoculated onto shredded cabbage was evaluated during storage in air or high CO2 controlled atmospheres (CA) of 5%, 10%, and 15% at 10℃ and in a modified atmosphere packaging (MAP) at 5℃ and 10℃. When shredded cabbage was inoculated with chlorine-injured E. coli O157:H7 (% injury = 65%) and then stored in air or CA at 10℃, counts of E. coli O157:H7 increased during storage and injured E. coli O157:H7 (% injury = 34-66%) were detected on samples throughout the storage regardless of the CO2 atmosphere. When shredded cabbage inoculated with chlorine injured E.coli O157:H7 (% injury = 45-59%) were stored in a MAP using either a high or low oxygen transmission permeability (OTR) package film, the counts of E. coli O157:H7 increased during storage at 10℃ and they remained constant during storage at 5℃. Injured E. coli O157:H7 were detected on shredded cabbage at a 54-56% level in a low OTR film at 10℃ and a 73-74% level in a high OTR film at 5℃. These results indicated that chlorine-injured E. coli O157:H7 inoculated on fresh-cut cabbage exhibited different degrees of injury during storage in a high CO2 CA and MAP at 5℃ or 10℃.
Staphylococcal food poisoning, which is still a serious health problem worldwide, is caused by staphylococcal enterotoxin (SE) . Among many types of SE, staphylococcal enterotoxin type A (SEA) is known to be the most responsible for staphylococcal food poisoning. Production by SEA-producing strains in shaking culture has been studied by many investigators, whereas the kinetical differences between shaking and stationary cultures have not been studied intensively. Therefore, this difference was studied at various temperatures from 14℃ to 46℃ in the present study. Consequently the maximum SEA concentration and populations of SEA producer in shaking culture was higher than those in stationary culture. Of interest, however, the productivity, which is the maximum SEA amount produced by one cell, in shaking cultures was lower than that in stationary culture. Kinetic analysis clarified that SEA gene expression in staphylococcal cells preceded toxin production at optimal temperature. Next, several SEA producers were studied for the maximum toxin production at various temperatures from 14℃ to 42℃ in shaking culture. Consequently all strains showed different patterns, suggesting that the characteristics of SEA production of these strains would be strain-specific. These results in this study would provide useful, basic information to prevent staphylococcal food poisoning outbreaks.
Few studies have evaluated the performance of air purifiers in removing airborne fungi in houses. Here, we evaluated the ability of a HEPA air purifier fan to remove airborne fungi in six houses in Japan. In each house, the number of airborne fungi decreased more rapidly when the air purifier fan was on (test measurement) than when it was off (control) , demonstrating its ability to decrease the fungal concentration. The number of airborne fungi decreased between 1.5 and 6 times faster when the air purifier fan was on than when it was off (spontaneous decrease) . Clean air change rates, calculated from measurements taken 15 min after the test equipment operation began, ranged from 2.9 to 5.4 (h-1) , indicating adequate air cleaning. One of the six test houses contained a much greater concentration of airborne fungi than the standard set by the Architectural Institute of Japan. When the air purifier fan was operated in the house, the indoor/outdoor (I/O) ratio decreased from 77.5, equating to a fungal concentration of 53,000 cfu/m3 at 0 min to 0.72 or 620 cfu/m3 after 45 min, which is below the standard. This reduction clearly demonstrated the antifungal effect of the air purifier fan.
Surface-acting agents are used as bread improvers in bread making to increase the specific loaf volume. We focused on the use of fatty acid salts as surface acting agents and new food additives. Fatty acid salts are the main components of soaps and display antibacterial activity. In this study, we investigated the mold-proofing activity and baking property with fatty acid salts. We examined the influence of fatty acid salts with different lengths of carbon chains on the dough expansion ability and found that the dough expansion ability increased significantly in the presence of more than 5% potassium myristate (C14K) . No significant difference was observed in the dough fermentation abilities between the control dough and C14K-treated dough, indicating of the absence of any effect of C14K on the fermentation ability. The antifungal test showed that C14K effectively inhibited fungal growth. Thus, C14K may serve as a promising bread improver.
BD mCCDA Clear-HT (CCHT; Nippon Becton Dickinson Company, Ltd.) , a novel chromogenic selective medium was evaluated for its superior capacity to isolate Campylobacter jejuni/ coli. When CCHT was assessed using 142 microbes including 42 Campylobacter jejuni/ coli strains, all Campylobacter strains were found to form purple-colored colonies on CCHT whereas all the other microbes failed to grow. CCTH was then compared with commercially available selective media using 100 stool samples including 40 Campylobacter positive samples. CCHT detected Campylobacter jejuni/ coli from 39 of 40 (97.5%) stool samples whereas it allowed competitive bacteria to grow as false positive colonies from 1 (1.0%) of 100 stool samples. The values of relative sensitivity (%) and specificity (%) for CCHT were 97.5 and 98.3 in this study. Our results demonstrated that CCHT had the highest detection ratio for Campylobacter jejuni/ coli and the highest inhibition ratio against competitive bacteria among all selective media compared.
MC-Media PadTM EB (MMP-EB) , a novel sheet culture method for the enumeration of Enterobacteriaceae, has been evaluated. When both inclusivity and exclusivity of MMP-EB were assessed using 104 microbes including 51 Enterobacteriaceae strains, all tested Enterobacteriaceae strains grew and formed obvious red-colored colonies and all tested non-Enterobacteriaceae strains were shown different appearance from Enterobacteriaceae strains. For the comparison study of the method, MMP-EB was compared with violet red bile glucose agar (VRBG) according to ISO 21528-2:2017 and PetrifilmTM Enterobacteriaceae Count Plate (Petrifilm EB) method using 100 naturally contaminated food samples. The correlation coefficients between MMP-EB and VRBG, and MMP-EB and Petrifilm EB were 0.940 and 0.972, respectively. Furthermore, there were no statistically significant difference between MMP-EB and both reference methods. Our results demonstrated that MMP-EB was a suitable alternative method for the enumeration of Enterobacteriaceae in food samples.
Acanthamoeba castellanii, a ubiquitous organism in water environments, is pathogenic toward humans and also is a host for bacteria of the genus Legionella, a causative agent of legionellosis. Fragrance ingredients were investigated for their antibacterial activity against planktonic Legionella pneumophila, amoebicidal activity against A.castellanii, and inhibitory effect against L. pneumophila uptake into A. castellanii. Helional® exhibited relatively high antibacterial activity [minimum inhibitory concentration (MIC) , 32.0 μg/mL] . Anis aldehyde, canthoxal, helional® and vanillin exhibited amoebicidal activity (IC50 values, 58.4±2.0, 71.2±14.7, 66.8±8.3 and 49.1±2.5μg/mL, respectively) . L. pneumophila pretreatment with sub-MICs (0.25×MIC) of anis aldehyde, canthoxal, cortex aldehyde® 50 percent or vanillin evidently reduced L. pneumophila uptake into A. castellanii (p < 0.01) . Thus, fragrance ingredients were good candidates for disinfectant against L. pneumophila and A. castellanii.