偽菌糸状に生育するSaccharomyces cerevisiae変異株J19を用いた細胞形態形成の解析

博士(工学)大阪市立大

Induction and inhibition of film yeast from fermented bamboo shoot by seasoning plants

Three samples of fermented bamboo shoot taken from a village in Amphur Kokpho, Pattani Province, were microbiologically examined. Total viable count was between at 104-105 cfu/ml while pH range was between 3.4-4.4. Isolation and identification of film yeast on surface of fermented liquid revealed Saccharomyces cerevisiae J1, Candida krusei J2 and Candida krusei J3. When film yeast was cultivated in liquid culture with different NaCl concentrations (0, 2.5, 5 and 7.5% (w/v)), all species tolerated 2.5% NaCl addition. However, growth decreased depending on NaCl concentration. S. cerevisiae J1 grew faster than C. krusei J2 and C. krusei J3. The cultivation of film yeast in medium with different agar concentrations (0.3, 0.5, 1 and 1.5% (w/v)) within 24 h showed that 0.3% was the optimal agar concentration. Seasoning plants (garlic, ginger, galangal, lemon grass, lesser galangal, clove, kaffir lime, garcinia and shallot) were extracted with water (3% (w/v)) and tested for growth inhibition. Results showed the clove extract inhibited all yeast strains within 12 h and after that the efficiency of inhibition was decreased. At low concentration of 0.75% (w/v) clove extract could inhibit film yeast in fermented bamboo shoot

Viability of Lactobacillus plantarum TISTR 2083 in protectant during low-temperature drying and storage

Low-temperature drying was applied as simple and low cost drying technique for the production of dried Lactobacillus plantarum TISTR 2083, which was isolated from traditional starter of Ka-nom Tuay-fu. To improve the survival of L. plantarum TISTR 2083 during drying and storage, five different protectants and two carrier materials were investigated. These include sucrose, trehalose, maltodextrin, skim milk, and L-glutamate sodium salt (L-GSS) as protectant and rice starch and rice flour as carrier material. Whereas, skim milk as protectant with rice starch resulted in higher viable cell (8.71 log CFU/g) after drying by hot air oven at 40 °C. Different concentration 5, 10, and 15% (w/v) skim milk also investigated to check the effect of skim milk concentration on cell viability. L. plantarum TISTR 2083 starter powder was in different storage conditions to check the storage stability. After 90 days of storage, starter powder stored at 4 °C with silica gel and without silica gel had more than 80% survival rate, while there was no viable cell that stored in room temperature with silica gel. The result showed the production and storage conditions of high viability L. plantarum TISTR 2083, which can be used as starter culture for further fermented product development and as probiotic

Extending the shelf-life of refrigerated green mussel (Perna viridis) under modified atmosphere packaging

The effect of modified atmosphere packaging (MAP) on the keeping quality of green mussel stored at 4C was investigated.Inhibition of the bacterial growth increased proportionally to the CO2 concentration in the packaging, and maximuminhibition was achieved with 100% CO2. Mussel stored under CO2-enriched atmosphere had lower total volatile base, trimethylamineand TCA-soluble peptide contents than those stored in air (P<0.05). However, the increase in exudate loss wasobserved for samples packaged in high-CO2 atmosphere, suggesting the denaturation of muscle proteins by carbonic acidformed. The odor and flavor acceptability of CO2-enriched packaged samples, particularly with 80 and 100% CO2, wasaccepted throughout the storage of 12 days, compared with six days for those stored in air. Therefore, MAP with 80% CO2,10% O2 and 10% N2 was chosen as the optimum condition for extending the shelf-life of green mussel. Packaging withinclusion of O2 should be considered to avoid the outbreak of strictly anaerobic toxin producing bacteria