Lab Report Sample

1. Sample Collection

Fermented milk products i.e. curd and lassi samples were purchased from a local dairy for isolation of lactic acid bacteria. Spoilt fruit samples were collected from local fruit market for isolation of spoilage-causing organisms. Good quality pineapples were purchased from the same fruit market for the preparation of juice.

2. Isolation and identification of bacteriocin producing LAB

The bacteriocin producers LAB were isolated from curd and lassi sample. The samples were diluted with sterile distilled water and 0.1 ml of the dilution was plated on MRS agar. After incubation for 24 hours at 37 °C, typical colonies were isolated and purified. The isolates were identified up to the genus level on the basis of their morphological, cultural, and physiological characteristics such as gram character, oxidase

Characterization of bacteriocins

6.1. Effect of temperature

The effect of temperature on bacteriocin stability was determined by exposing 5 ml aliquots of CFS at 40C, Room temperature, 370C, 630C and 1000C for 30 minutes. Agar well diffusion method was performed to determine the residual activity in the heat-treated CFS17.

6.2. Effect of pH

To check the pH stability of the bacteriocins, 5 ml aliquots of CFS was taken in sterile tubes and were adjusted to pH values of 2, 4, 7 and 9 busing 1N HCl or 1 N NaOH. After incubation at room temperature for 30 minutes, pH in each tube was readjusted to 6.5 and the antimicrobial activity was determined by agar well diffusion method17.

6.3. Effect of proteolytic enzyme

5 ml of CFS was taken in a test tube and was treated with trypsin-chymotrypsin enzyme (10AU/ml) at pH 7. The test tubes with and without enzyme (control) were incubated at 370C for 1 hour. After incubation, the enzyme was denatured by heating the tubes at 1000C for 5 minutes. Both the test treated and untreated samples (control) were assayed for antibacterial activity by agar well diffusion method15.

7. Antibiotic Sensitivity