CHARACTERIZATION AND IDENTIFICATION OF LACTOBACILLUS ACIDOPHILUS USING BIOLOG RAPID IDENTIFICATION SYSTEM

Abstract

Objective: The present study was carried out to isolate and identify L. acidophilus and to compare the effect of inoculation methods and cultivation conditions on the yield of the bacteria. Methods: Probiotic Lactobacillus strain was isolated from a commercial yogurt and the characterization of the bacteria was performed using gram stain, motility, catalase, biochemical tests and morphological features were confirmed using scanning electron microscope (SEM). Finally the identification was confirmed by BioLog system. Effect of inoculation methods and cultivation conditions on the growth and yield of the bacteria were studied. Results: The isolated strain was Gram positive cocco-bacilli, nonmotile and catalase negative. It ferment maltose, lactose, sucrose, and glucose, but unable to ferment arabinose and sorbitol. The SEM examination displayed the ranging of the cells varied from 2.02 - 5.49 × 0.50 - 0.59 µm. From all the results it is confirmed that the species is Lactobacillus acidophilus. In addition, Biolog rapid identification system revealed the presence of L. acidophilus in the prepared samples with 90% indexed probability. Pour plate provided a relatively higher viable count than the spread plate, while no significant differences were observed between aerobic and anaerobic conditions. Conclusion: The bacterial strain was successfully isolated after series of purification. It was identified as Lactobacillus acidophilus. It can be concluded that, a carbon utilization microplate assay system developed by Biolog, has the potential to simplify the identification scheme of lactic acid bacteria to the genus level.