Technological properties of lactobacillus rhamnosus k3 isolated from fermented cabbage and its potential use as starter culture for fermented food products

Abstract

The objective of the research study was to specify technological properties of the Lactobacillus rhamnosus K3 strain. This bacterial strain was tested for its ability to grow under the processing conditions, such as temperature [ºC]: 10, 15, 45, pH value: 3.9, 6.4, 9.6, and a high NaCl concentration [%]: 5, 8, 10. Biochemical tests (sugar fermentation and enzyme activity) were carried out and the survival of those bacteria was assayed in the medium depending on the type of food (milk, tomato juice, and beef broth). Milk fermented with Lb. rhamnosus K3 was subjected to 6-week incubation. The results showed that the Lb. rhamnosus K3 strain was able to grow at different temperatures but within a narrow pH range. The bacterial strain did not tolerate high NaCl concentrations, however it grew well in any kind of food medium. A particularly good bacterial growth was observed in milk. Lb. rhamnosus K3 was able to metabolize sugars. This strain did not reduce nitrates; no catalase activity was detected either. The β-galactosidase enzyme was identified. The best temperature of milk fermentation was proved to be 37 ºC. It was also found that Lb. rhamnosus K3 had functional properties allowing its use as a starter culture for milk. The number of bacterial cells remained at a level higher than 8 log CFU/ml throughout the entire 6-week incubation of refrigeration storage (4 ºC). The bacteria of Lactobacillus rhamnosus K3 were capable of fermenting milk confirming their suitability as a starter culture for milk products.