การเปลี่ยนแปลงของประชากรแบคทีเรีย และชีวเคมี ในการหมักน้ำปลา / สาโรจน์ ประเสริฐศิริวัฒน์ = Bacterial population and biochemical changes in fish sauce fermentation / Saroch Prasertsirivatna
Study for the selection of appropriate media suitable for the isolation of bacteria from fish sauce indicated that tryptone yeast extract agar is the most suitable medium by which the medium gave the highest number of bacteria as well as type of bacteria. The optimum incubation time for low salt tolerance bacteria and halophilic bacteria were 8 days and 14 days respectively. Results of the study for the change of bacterial population during the course of fermentation indicated that the maximum number of bacteria was found in the first day of fermentation in which most of the bacteria found were gram positive cocci with low salt tolerance nature, with the rest of gram positive and gram negative rod. The number of such bacteria was reduced rapidly during the first two weeks of fermentation. Afterward, a predominate halophilic bacteria with red color colony appearance took place then peaked at 62 days and disappeared after 124 days. The presence of this group bacteria were found correlated with amount of total nitrogen, amino acid nitrogen and ammoniacal nitrogen, total free amino acid as well as their change which were found constant after 4 months of fermentation, pH of the culture was found in the range between 5.22 - 5.96 and continuously declined after day 86. Isolation for halophilic protease producer showed that isolate 1 which gave highest protease and gelatinase activity possesses morphological as well as biochemical characteristics resemble those of Halococcus should be a good candidate for this purpose. Artificially inoculated with isolate 1 gave higher total nitrogen and amino acid nitrogen but less ammoniacal nitrogen content in comparison to natural fermentation
