Title : Technological properties and antibiotic susceptibility (MIC) of isolates from fresh and ripened LIGHVAN cheese
In this research we discuss about some technological properties such as acid tolerance, lipolytic and proteolytic activities also antibacterial activity and minimum inhibitory concentration (micro broth dilution method) of three antibiotics against enterococci isolates Lf 44 and Lf 54 (from fresh cheese) and LR71, LR74 and LR75(from ripened cheese). Clear zone around colonies was indicated lipolytic activity, in our results none of isolates were able to hydrolyze tributyrin agar. Weak lipolytic activity can be positive aspect for bacteria because of increasing the shelf life by reducing the rancidity products.
Proteolytic activity which is the main reason for cheeses ripening by hydrolyzing proteins to amino acids and improvement organoleptic properties, observed in all 5 isolates that LF54 and LR74 had significant halo zone in comparison to other isolates. Acid tolerance and survival rate of each isolate (after preparing 0.5 McFarland solution) was measured by counting colonies at 0 h and 3 h in pH 2.5. In our study LR74 and LR75 had high and >90% tolerance to this condition, respectively and LR71 with 80% survival. Antibacterial activity was assayed by a well diffusion method against food-borne pathogen Listeria innocua. Clear zones were observed around each isolate except LR71.
Antibiotic susceptibility of isolates was determined against Gentamycin, kanamycin and chloramphenicol by micro broth dilution method and using 96 well plates. The first well with no bacterial growth indicates minimum concentration of antibiotic that prevent bacterial growth. By concern of standards defined by CLSI, sensitive(S) and resistance (R) of each concentration was determined. Our results showed all isolates were sensitive to all antibiotics except LR71 that was resistance to chloramphenicol. In according to our study, isolates from ripened cheese LR75 and LR74 showed acceptable results in these tests specially survival rate in acidic environment which is lead to evaluation probiotic aspect of them in future.
Audience Take Away:
- In according to our study, isolates from ripened cheese LR75 and LR74 showed acceptable results in these tests specially survival rate in acidic environment which is lead to evaluation probiotic aspect of them in future.