Fermentation Capability And Proteolytic Activity of Lactic Acid Bacteria in Milk and Comparison of Antifungal Activity of Lactic Acid Bacteria in Skim Milk and MRS

In this study, milk fermentation capability by 6 isolates of lactic acid bacteria, proteolytic activity of lactic acid bacteria in milkby ortho-phthaldialdehyde (OPA)reagentand antifungal property of lactic acid bacteria in MRS broth and skim milk against Aspergillus flavus and Candida albicanswere studied. L. brevis KMJC1, L. acidipiscis KMJC2, L. curvatus KMJC3 and L. plantarum KMJC4 isolated from Jug cheese, L. helveticus KMCH1 isolated from camel doogh (Chal) and Lac. lactis KMCM3 isolated from camel milk were used. The results showed thatamong the isolates,L. plantarum KMJC4after 48 h, Lac. lactis KMCM3 after 16 hand L. helveticus KMCH1 after 60 hhad milk fermentation capability. The measurement of proteolysis rate performed infermented milk by mentioned isolates using OPA reagent indicated that the proteolytic activity of L. helveticus KMCH1, Lac. lactis KMCM3 and L. plantarum KMJC4 were 0.34, 0.26 and 0.22 mg/ml, respectively. In study of the antifungal effect of supernatant resulting from the activity of lactic isolates, it was found that supernatant obtained from culture in MRS broth had a more inhibitory effect (MIC= 25 and 50 mg/ml) than the supernatant obtained from the culture in the skim milk, as the MIC was not observed for the supernatant obtained from fermented milk. In the end, it can be concluded that Lac. lactis KMCM3 was able to ferment lactose in milk in comparisonwith other isolates in shorter time (16 h). The highest proteolytic activity of the isolates in milk was related to the isolate of L. helveticus KMCH1 (0.34 mg/ml). L. plantarum KMJC4 isolated from Jug cheese was as the best isolate for the preparation of supernatant resulting from MRS broth with the antifungal property.