Screening of Bacterial Isolates Producing Diacetyl and Selecting the Most Efficient Isolate

Abstract

Screening number of bacterial isolates in term of their ability to produce diacetyl from five samples of different dairy products include Qargoli cheese (Q and K) from two sources, Akkawi cheese (A), Soft cheese (S) and local butter (B), were purchased from the local market of Al-Ramadi city/Anbar province, the colonies were picked up from culture medium MRS and M17 after incubation 24 to 48 hr at 37C in anaerobic conditions and examined in microscopic (rod and cocci) Single, double and Strings, gram-positive and non-spore forming, we collected 7 colonies from 21 colony, 2 isolates from cheese (K) on M17 medium were cocci, 3 isolates from cheese (Q) on MRS medium were cocci, 1 isolate from cheese (A) on M17 medium was rod ales 1 isolate from cheese (S) but on MRS medium was rod, as for butter (B) no result, were shown under the same conditions, the 7 isolates subjected to a qualitative detection of their ability production and gave a positive indicator for Voges-proskauer test and Brady's reagent to varying degrees between them, then the production of diacetyl for 4 isolates with the highest productivity, were quantified by Westerfeld method and HPLC technique, with Westerfeld the concentrations were 171.197, 234.654, 217.617, 222.926 μg/ml for K2, Q3, K4 and K7 respectively at absorbance 540 nm, isolate Q3 and K7 were distinguished with highest productivity of diacetyl by HPLC reached 5.7 and 5.9 ppm respectively.