好気性芽胞細菌の食品細菌学的研究(II)
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概要
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In the present paper the results of laboratory experiments on the significance of sporeforming bacteria as the organisms causing spoilage of food are given. The results obtained are summarized as follow. 1) Certain species of sporeforming bacteria excepting B. subtilis group were isolated from spoiled food materials, soil and water samples The cultural characteristics of all isolates were observed in detail. Thirty-three strains were classified into four species and one group according to the key of Bergey's manual and R. N. Smith's discription on this genus. Polymyxa-macerans group…12 strains, Bacillus circulans…6 strains, B. alvei…3 strains, B. laterosporus…3 strains, B. brevis…9 strains. 2) Proteolytic and saccalolytic activities Gelatine liquefaction was positive 30 strains out of 33. Casein hydrolysis also positive in 91 % of tested organisms. Hydrolysis of starch was positive in most cases, while a few strains belonging B. brevis and B. laterosporus were negative. 3) Single inoculation test on various food materials Plant food: Rice and boiled vegetables were easily attacked by many strains of organism. But the strains of B. brevis and laterosporus showed no sign of deterioration of rice. Animal food: The intensity of putrefaction in fish material, raw and cooked, was differ in the strains which were tested. Some strains spoiled fish strongly but others attacked rather weakly and slowly. 4) The putrefactive activities against fish meat was tested by means of measurement of the quantity of NH_3-N which was produced by inoculated bacteria. It most cases, NH_3-N increase was remarkably high. But if the bacteria were grown in anaerobic condition in substrate, NH_3-N production was less amount comparing with the case in aerobic condition. 5) Susceptibility to chemical agents Antibiotics: All strains were highly sensitive to chlortetracycline, chloramphenicol, streptomycin. The growth of bacteria was inhibited at the concentration of 10 mcg/ml of antibiotics.But the three strains of B. alvei were strongly resistant against Penicillin. Chemical preservatives: The isolates were also sensitive to furan derivatices, such as nitrofurazone and Z-furan. 6) NaCl resistance The growth was inhibited in 10 % NaCl medium. Especially B. polymyxa and B. macerans were relatively sensitive and there were no strains grew in 5 % NaCl medium.
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