Instability of nata formation by Acetobacter aceti Subsp. xylinum
1987
Flores, F.C.F. | Sanchez, P.C. (Philippines Univ., Los Banos, College, Laguna (Philippines). National Inst. of Biotechnogy and Applied Microbiology)
A total of 32 isolates were obtained from nata mother liquor and evaluated for their ability to produce nata in glucose-yeast extract and coconut water (CWM). The best isolate was selected for further tests and identified to be Acetobacter aceti subsp. xylinum. It proved stable in sterile CWM but in non-sterile medium was able to produce nata for only six successive transfers. It grew best at 6% sugar, pH 3.5, and incubation temperature of 35 deg C. Contaminants significantly affected nata formation. The yields of nata and the total plate counts of the nata organism decreased with increased total bacterial and yeast counts. Pichia and candida formed films on top of the fermenting medium and competed for space and oxygen with the nata organism, an obligate aerobe. Other contaminants were Saccharomyces, Acetobacter, Bacillus, Leuconostoc, and Pediococcus. The buildup of these contaminants was accomplished with decrease in pH, lactic acid and alcohol levels and increase in acetic acid content in non-sterile CWM.
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