Antimicrobial activity of probiotic Lactobacillus strains towards Salmonella enterica ser enteritidis in whey
N Goyal, K Dixit, D Gandhi
lactic acid, probiotic, whey
N Goyal, K Dixit, D Gandhi. Antimicrobial activity of probiotic Lactobacillus strains towards Salmonella enterica ser enteritidis in whey. The Internet Journal of Microbiology. 2007 Volume 5 Number 1.
Past decades have witnessed the applications of probiotics in the prevention and management of gastrointestinal disorders (Heyman and Menard, 2002).These microbes are designed to improve intestinal microbial balance and partake in normal bacterial-epithelial crosstalk and offer a potential promising approach to the management of intestinal problems caused by stress (Servin, 2004).
Different probiotic species and even different strains within a species exhibit distinctive properties that can markedly affect their survival in foods, fermentation characteristics and other probiotic properties. Among various species,
Barely few years ago, whey was merely a by-product of cheese and paneer industry, which was usually dumped because it had no value; a practice that was increasingly frowned upon by environmentalists. .Available literature on application of whey in controlling gastrointestinal disorders is not ample. The lactic acid bacteria possess the ability of lactose utilization and hence can form a better resource for maximum lactose bioconversion in whey (Gupta and Gandhi, 1995). The aim of the experiment was to study the ability of
Material and methods
Maintenance and propagation of cultures
Lactic acid estimation in cell free supernatant
The concentrations of D-L Lactic acid in cell free supernatant obtained from MRS and whey of selected cultures was determined using commercial enzymatic kit (Test Combination D-Lactic acid / L-lactic acid UV method; Boehringer Mannheim Gmbh, Germany).
The sample preparation is required for the colored, acidic, fermented samples of MRS and whey. Accurately weigh approx. 1 to 10 ml of cell free supernatant into 100ml volumetric flask. Add 50ml of warm water. For clarification, add 5ml Carrrez-I solution (3.60g potassium hexacyanoferrate II), 5ml Carrrez II solution (7.2 g zinc sulphate) and 10ml (0.1M) NaOH and 1 ml of filtrate was used for lactic acid assay.
killing assay for anti activity
The inhibitory activity of fermented whey CFCS of probiotic cultures towards
The experimental data are presented as the mean (SEM). General Linear Model (GLM) procedure with post hoc test was applied to determine whether significant differences existed among different cultures using SYSTAT 6.0.1 Statistical Software Package, 1996, SPSS, Inc., USA. The predetermined acceptable level of probability was 5% (P< 0.005) for all comparisons
Analysis of Lactic acid concentration of selected cultures
Lactic acid concentration was determined by Boehringer Mannheim D-L Lactic acid kit in the selected best probiotic cultures. After culturing for 24 o C at 37 o C in MRS broth (containing glucose) as shown in Fig 1 and whey (without any nutrients) as shown in Table 1, lactic acid concentration in cell free supernatant (CFS) was determined.
D-L isomers of lactic acid was estimated in all the seven whey samples inoculated with seven probiotic lactic cultures after an incubation period of 24 hrs. Lactic acid concentration in whey reaches maximally up to 29mM (Table 1) for NCDC 291 followed by NCDC 299 and NCDC 17. The low lactic acid concentration resulted in lesser diffusion in agar well method. Moreover, the findings showed that only NCDC 17 produces more of D-lactic acid (7.2mM/l) as compared to other probiotic strains in fermented whey. Low lactic acid concentration was shown by strains DDS-1 and MTCC 1408.
All selected cultures produced L- lactic acid during MRS fermentation in the range of 60Mm – 80mM with a little amount of D-lactic acid. Only
Time dependent inhibitory or killing activity of fermented whey
The findings indicated that fermentation of whey with seven
With respect to the production of enzyme in MRS, whey due to lack of specific nutrients is not a good medium for β-galactosidase enzymatic activity. It is based on simple conclusion that MRS medium is composed of rich nutrient source as compared to whey and thus lactic cultures grow better in glucose based medium.
It is noteworthy that L-lactic acid, displays a greater antibacterial activity than D-lactic acid in the CFCSs (Fayoul-Messaoudi
High anti bactericidal activity of MRS as compared to whey is due to higher nutritional property of selection medium which affects the production of antimicrobial isolates by
The major weapons to combat the enteric enemies, a property endorse by fermented whey are the organic acids. Short chain fatty acid (SCFA), such as acetic acid, citric acid and lactic acid which are the major metabolites of lactic acid bacteria have been reported to be responsible for their antimicrobial activity against pathogens in intestine. Among all the organic acids, lactic acid is the best in inhibiting the proliferation of bacteria that causes putrefaction.
The mechanism involved, is that the undissociated form of the organic acid enters the bacterial cell and dissociates inside the cytoplasm. The eventual lowering of the intracellular pH or the intercellular accumulation of the ionized form of the organic acid, lead to the death of the pathogen (Makras and De Vyust, 2006).Complete inhibition of growth occurred consistently at approximately 10mM undissociated lactic acid for total lactic acid concentrations of 25mM to 100mM (Presser