Toshihiro Yano

Colorimetric alamarBlue assay as a bacterial concentration and spoilage index of marine foods

Abstract The alamarBlue (resazurin) assay incorporates a colorimetric and fluorometric growth indicator based on detection of the metabolic activity of cells. We investigated the relationship between results of the colorimetric alamarBlue assay using 96-well microplates and colony-forming units (CFU) on aerobic agar plates of Escherichia coli, Staphylococcus aureus, Bacillus subtilis strains and unknown bacterial flora in spoiled foods. As bacteria grew in a TYG broth containing alamarBlue (TYG/A), they converted the color from a blue oxidized state to a red reduced state. When 105 CFU of the mesophilic bacteria were placed in a well, the time for converting the color required from 2 to 4 h at 37 °C incubation. In the case of pork and saury fish meats stored at 4 °C, the alamarBlue reduction, value, performed by OD 550–595 nm in the TYG/A incubated for 4 h, increased with the CFU/g meat. These results suggest that the procedure using alamarBlue assay can provide a simple, rapid, low technology, low cost and compact experiment to determine bacterial growth and spoilage of foods including marine foods.

Fermentation of Autoclaved Beans by Bacillus subtilis(natto).

ダイズと納豆菌の選択性を検討するため,オートクレーブ処理後,納豆菌を接種した豆6種類およびハス(はすの実)の,発酵過程における菌数,糸引き,水溶性タンパク,遊離L-グルタミン酸,アンモニアなどの変化を調べた.菌数や糸引き度の増加および各化学成分の上昇がダイズ,特に黄豆を発酵させたものにおいて最も明確に認められた.これらの発酵過程の変動はインゲンマメ,エンドウあるいはハスでもある程度認められたが,アズキでは認められなかった.