The present study was designed to achieve three goals: (1) to investigate some physical properties of the crude antimicrobial substance (lactobulgarican) produced by Lactobacillus bulgaricus, (2) to test the effect of several types of sugar present in the growth medium of L. bulgaricus on production of lactobulgarican, and (3) to purify and characterize the pure lactobulgarican. / Lactobulgarican was located extracellularly and was more active toward gram-negative than -positive organisms. It had an optimum pH of 4.0. It was reversibly inactivated at pH range of 5.0-12.0 but irreversibly inactivated at pH 1.0. At the optimum pH, lactobulgarican was highly thermostable. It was also stable to refrigerated storage up to 18 days. / Carbohydrate-free formula, with a given type of sugar added, was used to test the effect of sugar on lactobulgarican production. Among the sugars tested, glucose produced the lowest pH value and the largest inhibition zone under a short incubation period, i.e., 48-hours. Under a long incubation period, i.e., 96-hours, both glucose and lactose, at the same concentration, produced comparable results. A ninety-six hour incubation period was the best one among those tested. Fructose and sucrose were not fermented by L. bulgaricus, and did not produce any inhibition zones. / Reversed phase HPLC column was used to purify lactobulgarican. Lactobulgarican did not contain lactic acid or hydrogen peroxide. The UV spectrum of lactobulgarican produced two broad peaks at 198 and 274 nm. Negative and positive chemical ionization mass spectra produced peaks at m/e 181, 180, 163 and 179, 91, 88, 57, respectively. The biuret test for lactobulgarican was negative. Results from the UV and mass spectra indicated the possible presence of a hexose and a phenol-containing compound, possibly phenylalanine. The molecular weight of lactobulgarican was (LESSTHEQ) 507. / Source: Dissertation Abstracts International, Volume: 46-01, Section: B, page: 0012. / Thesis (Ph.D.)--The Florida State University, 1984.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75497 |
| Contributors | ABDEL-BAR, NADIA MOKHTAR., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 202 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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