This report describes the synthesis of an antibacterial material consisting of a gemini quaternary ammonium salt (gemini-QUAT) immobilized on ferrite powder, and its antibacterial activity. A gemini-QUAT containing two pyridinium residues per molecule, 4, 4'-[1, 3-(2, 2-dihydroxylmethy1-1, 3-dithiapropane)] bis (1-octylpyridinium bromide), was immobilized on ferrite powder by a reaction between the hydroxyl group of the QUAT and trimethoxysilane. Immobilization of the gemini-QUAT on ferrite (F-gemini-QUAT) was confirmed when the dye, bromophenol blue, was released from F-gemini-QUAT-dye after contact between ferrite and the dye. Elemental analysis of the QUAT-ferrite determined the molar amount of QUAT on the ferrite. The antibacterial effect of the ferrite was investigated using a batch treatment system, and this effect was compared with that of another QUAT-ferrite (F-mono-QUAT) binding a mono-QUAT, which possesses one pyridinium residue, prepared by the same immobilization method as F-gemini-QUAT. Results indicated the F-gemini QUAT possessed a higher bactericidal potency and broader antibacterial spectrum compared to F-mono-QUAT. In addition, this study suggested that gemini-QUATs possessed high bactericidal potency without being influenced by immobilization to materials, and the antibacterial activity and characteristics of Fgemini-QUAT could be attributed to the unique structure of the immobilized gemini-QUAT.

View full abstract

The antibacterial activity of a disinfectant with geminated twin long-chain alkyl groups, didecyldimethylammonium chloride (DDAC), was investigated. The minimum inhibitory concentration (MIC) value of DDAC against Eschrichia coil was revealed to be a small value, 1.3 mg/L, by using the specific growth rates, μ, obtained from the cultivation in a liquid nutrient broth (NB) medium. The relationship between the leakage of proteins or β-galactosidase and the DDAC concentration showed that the leakage of intracellular macromolecules occurs at around 3-4 mg/L DDAC. Furthermore, the effect of DDAC on the enhancement of membrane fluidity was examined by using liposomes labeled with a fluorescent probe. It was shown that the phase transition occurs at around 3 mg/L DDAC. The bleb formation of E. coli cells in the presence of DDAC was also examined by use of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). However, bleb formation was not observed at around3 mg/L DDAC but at concentrations higher than 50 mg/L. These results suggested that the action of DDAC toward the cell membrane causes the leakage of the intracellular molecules and the subsequent death of the cells. Thus the bleb formation seemed to be a result of the action of the DDAC toward the cell membrane but not to be a reason for the death of the cells.

View full abstract

Hinokitiol, the major component of Aomori Hiba (Thujopsis dolabrata Sieb. et Zucc. var. hondai M_AKINO) has already been found to show strong antibacterial activity. In this study, its mechanism of action was examined using EscherIchia coli IFO 3301 and Staphylococcus aureus IFO 12732. As a result, it was suggested that at least a part of the mechanism of the bactericidal action of hinokitiol was due to the metabolic inhibition of the cell membrane in connection with the permeability of the cell membrane and respiration from the following three points. Firstly, from examination of the portraits of electron micrograph of E. coli IFO 3301 and S. aureus IFO 12732, no morphological change was found in the group treated hinokitiol as compared with the control group. Secondly, the respiration of both bacteria was remarkably suppressed by the addition of hinokitiol. Thirdly, incorporation of [U-¹⁴C] -labeled adenine into low molecular and nucleic acid moiety of cell bodies of both bacteria was strongly inhibited by the addition of hinokitiol. Strong suppression was also found in the incorporation of [U-¹⁴C] -labeled amino acid mixtures into low molecular and protein moieties of cell bodies of both bacteria treated with hinokitiol.

View full abstract

As the microbial contributions to the processing of salted foods have been little investigated, there remains a possibility that excess sterilization of raw materials for salted foods leads to deterioration in food quality and safety. At a salmon roe (sujiko) processing company, we investigated salted sujiko made identically to commercial products, but that had been processed with or without antibiotics. The antibiotics caused no significant difference in the content of free amino acids, lactic acid or acetic acid. These results show that general aerobic bacteria have no impact on the formation of these flavor compounds.

View full abstract

Transformation phenomena occurring under conditions mimicking the biofilm environment were investigated using Escherichia coil IM302 (as DNA recipient cells) and Providencia sp. WW2 (as surrounding cells in the biofilm model). In the case of planktonic IM302 cells kept at 25°C, the transformation took place exclusively in the absence of organic nutrients (COD=0), and was not substantially observed in the range of COD=30-1500 mg 0₂/L. On the other hand, in the case of biofilm IM302 cells, the transformation occurred at relatively high levels under the examined conditions (temperature=5 or 25°C and COD=0-1500 mg 0₂/L). These results indicated that the competency of biofilm IM302 cells was induced even in the presence of organic nutrients owing to nutritional starvation caused by WW2 cells.

View full abstract

Poly (ε-caprolactone) (PCL) is one of the commercial biodegradable plastics and biocompatible polyesters that can be assimilated by microorganisms. Lysinlbacillus sp.70038 which degrades PCL film was screened from stock cultures by cultivation using an enrichment culture medium containing PCL film with the weight-averaged molecular weight (Mw) of 160, 000 as a sole carbon source. Lysinibacillus sp.70038 degraded 9.0% of PCL at 30°C, 100 rpm, after 30 d. Scanning electron microphotograph (SEM) analysis of the degraded PCL film showed nearly 4μm of surface erosion, and the molecular weight distribution of the surface area of PCL film became broad and a low molecular weight polymer (Mn=6, 900) was confirmed by gel permeation chromatography (GPC) after cultivation.

View full abstract