The ability of heated scallop-shell powder (HSSP) to disinfect Escherichia coli ATCC 25922 biofilm was investigated. On account of its cryotolerance and cell surface characteristics, the E. coli strain is reportedly a useful surrogate for E. coli O157: H7 in surface attachment studies. In this study, an E. coli ATCC 25922 biofilm was formed on a glass plate, and immersed in a slurry of HSSP. Following treatment, the disinfection ability of the HSSP toward the biofilm was non-destructively and quantitatively measured by conductimetric assay. The disinfection efficacy increased with HSSP concentration and treatment time. HSSP treatment (10 mg/mL, pH 12.5) for 20 min completely eliminated biofilm bioactivity (approximately 10 8 CFU/cm 2 in non-treated biofilms). In contrast, treatment with NaOH solution at the same pH, and treatment with sodium hypochlorite (200 g/mL) reduced the activity by approximately one to three log 10 . Fluorescence microscopy confirmed that no viable cells remained on the plate following HSSP treatment (10 mg/mL). Although alkaline and sodium hypochlorite treatments removed cells from the biofilm, under these treatments, many viable cells remained on the plate. To elucidate the mechanism of HSSP activity against E. coli ATCC 25922, the active oxygen generated from the HSSP slurry was examined by chemiluminescence analysis. The luminescence intensity increased with increasing concentration of HSSP slurry. The results suggested that, besides being alkaline, HSSP generates active oxygen species with sporicidal activity. Thus, HSSP treatment could also be effective for controlling biofilms of the toxic strain E. coli O157: H7, implicated in food poisoning.
Kishu-Narezushi is a spontaneously fermented food comprising fish, rice, and salt. During spontaneous fermentation, the microbiome may differ among batches, even when manufactured in the same way. In addition, analyses of changes in chemical composition of the product are important for clarifying flavor characteristics.
We collected basic information on the microbiome and chemical composition of Kishu-Narezushi using multiple batches of fermentation, and evaluated whether the microbiome was homogeneous.
The fungal microbiome of Kishu-Narezushi was dominated by Saccharomycetales and Trichosporonales. The bacterial microbiome was diverse, although seven specific genera of lactic acid bacteria were identified. Glutamic acid, histidine, and serine levels decreased after approximately 10 days of fermentation. Succinic acid, characteristic of Kishu-Narezushi, accumulated upon the consumption of glutamic acid.
Though the microbiome was diverse, the chemical composition was similar among the batches.
The semi‐artificial branched‐polysaccharides, amylose‐grafted curdlans, were synthesized utilizing an enzymatic polymerization. Both a curdlan main chain and amylose side chains on the polysaccharides maintain the original helical structure as well as the molecular binding ability. Thanks to the difference in their molecular recognition properties between β‐1,3‐glucan chain and α‐1,4‐glucan chain, the amylose‐grafted curdlans can provide two different orthogonal binding sites within one polymeric system. When a water‐soluble polythiophene was mixed with the amylose‐grafted curdlan, the polythiophene was twisted in two different modes and therein, fluorescence energy of the polythiophene wrapped by the amylose side chains was successfully transferred to the polythiophene wrapped by the curdlan main chain. We thus concluded that in the dendritic superstructure of this polysaccharide, a self‐organized “Janus‐type FRET system” was successfully constructed.
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