BIOCHEMICAL AND GENETIC IDENTIFICATION OF TWO LOCAL DIACETYL PRODUCER BACTERIAL ISOLATES

Four local bacterial isolates (Q3, K7, K2 and K4) were selected that were isolated from Qargoli cheese with the ability to produce diacetyl , all isolates showed a negative result in the catalase test, they fermented glucose when grown at 20 and 37 oC but all of them were unable to grow at 45 oC , the isolates K2, K4 and K7 in MRS broth and Q3 in M17 broth tolerated 0.5% and 2% NaCl excepted K7 , isolates K2 and K4 were able to grow at 5% NaCl ,the tested isolates were not tolerated 10% NaCl , isolates have acidic activity in skim milk and all of them gave a white clot that ranged from soft to very soft, isolate K4 ranked first in diacetyl production 59.59, 68.36 and 179.09 µg/ml at of 0.05, 0.1 and 0.15% sodium citrate concentration. Genetic examination proved that isolate Q3 is Lactococcus lactis strain HANM Diacetyl and K7 is Pediococcus pentosaceus strain Bro DiAc.