Investigation of Bacteriocin Production Potentials of Lactic Acid Bacteria Isolated From Raw Milk Samples

3. Avrasya Biyokimyasal Yaklaşımlar ve Teknolojiler (EBAT) 2021 , Antalya, Türkiye, 4 - 07 Kasım 2021, ss.89

Lactic acid bacteria (LAB) which are Gram (+), catalase (-) and non-spore-forming are accepted as

microorganisms producing lactic acid as the main end product as a result of their carbohydrate

metabolism. LAB lowers the pH of the environment due to the lactic acid they produce, and they

produce acid at these low pH's. LAB, which has an inhibitory effect on many bacteria, hamper the

development of pathogen and contaminant organisms with substances such as lactic acid, hydrogen

peroxide, diacetyl and bacteriocin they produce.1 Since LAB produces these substances, they are very

important in the protection and safety of the food product and these bacteria are regarded as reliable

(GRAS) bacteria that have been used as a preservative culture in food production for many years. LAB

are isolated from nutrient-rich media containing soluble carbohydrates, vitamins and proteins. They

are abundant in meat, fruits, vegetables and dairy products, they are also found in the intestines and

mucous membranes of mammals, in manures and wastewater.2 In our current study, 18 isolates were

obtained from 7 raw milk samples obtained from Erzurum province and these isolates were

characterized phenotypically in the first stage. The isolates, whose morphological and physiological

analyzes were performed, were then distinguished from each other on the basis of species by genomic

fingerprint analysis [rep-PCR (GTG5 and BOX PCR)]. As a result, 5 isolates considered to be different

were genomically identified by 16S rRNA sequence analysis. At the first stage, antimicrobial properties

of 5 identified isolates were tested against Salmonella typhi, Staphylococcus aureus, Listeria

monocytogenes, Bacillus cereus, Escherichia coli, Yersinia enterocolitica and Candida albicans.

Simultaneously, specific PCR analysis was performed to determine whether these 5 isolates contain

the relevant bacteriocin genes (Plantaricin, Lactocococin, Pediocin, Brevicin, Nisin), determined by

species at the genomic level. As a result of these two methods, it was determined that the ET2 isolate

had strong antimicrobial effects against Staphylococcus aureus and Bacillus cereus and this isolate was

a strong nisin producer. It was detected that as a result of 16S rRNA sequence analysis of the ET2

isolate, which has an antimicrobial effect and the potential to produce bacteriocin, ET2 showed 99%

similarity to the Enterococcus durans species, and then this isolate was biochemically analyzed with

the RapiD 20E System (bioMérieux, France).