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Isolation and Characterization of Lactic Acid Bacteria from Raw Milk and 'Kesong Puti' (White Soft Cheese)
Thesis Abstract:
The study was conducted to isolate and study the diversity of LAB in indigenous cheese ‘kesong puti’ and raw carabao’s and cow’s milk. Highest putative LAB counts were obtained from ‘kesong puti’ made from unpasteurized carabao’s milk. There was no significant difference in putative LAB counts under aerobic and anaerobic incubation conditions. The log putative LAB counts were found to be significantly negatively correlated with the pH of the cheese and raw milk, r = -0.9999. No significant correlation was found among the log putative LAB count, moisture, and salt contents of cheese.
The LAB isolates were characterized phenotypically and identified as Lactobacillus helveticus, Lactococcus lactis lactis, Lactobacillus rhamnosus, Leuconostoc mesenteroides subsp. dextranicum 2, Lactobacillus plantarum, Lactobacillus acidophilus, Lactobacillus brevis, and Lactobacillus curvatus. The results seemed to show a potentially large diversity of LAB. None of the 23 LAB isolates identified showed antimicrobial/bacteriocin activity against Pseudomonas fluorescens (Biotech No. 1123). Thirteen LAB isolates were found to be active culture with lactic acid (LA) production of 0.04 percent and higher after 2-hour incubation. These cultures were two isolates of Leuconostoc mesenteroides subsp. dextranicum 2, four isolates of L. plantarum, two isolates of L. rhamnosus, one isolate of L. acidophilus and four isolates of L. lactis lactis. None of the isolates produced diacetyl.
Among the three Genera, Genus Lactobacillus was found to be the fastest growing with generation time of 1.5511 hours and a specific growth rate of 0.5017 growth/hr followed by Genus Lactococcus with generation time of 1.97373 hours and a specific growth rate of 0.4017 growth/hr. Genus Leuconostoc was the slowest with generation time of 2.7304 hours and a specific growth rate of 0.2850 growth/hr.
The organisms were freeze-dried after they were grown to late logarithmic phase in skim milk.
The LAB isolates were preserved by two methods: freeze-drying and stab cultures overlaid with sterile mineral oil for future potential applications.