Acid and Bile Salt Tolerance of Presumptive Lactic Acid Bacteria Isolated from Tamarind (Tamarindus indica L.) Pulp

Abstract

Probiotics are mostly dairy-derived, whereas acidic tropical fruits remain underexplored sources of lactic acid bacteria. Tamarind (Tamarindus indica L.) pulp is highly acidic, and, to our knowledge, its lactic acid bacteria have not been evaluated for acid and bile salt tolerance. This study aimed to isolate presumptive lactic acid bacteria from ripe tamarind pulp and screen their in vitro acid and bile salt tolerance. Bacteria were isolated on de Man, Rogosa and Sharpe agar with 0.5% calcium carbonate and characterized by colony morphology, Gram staining, and the catalase test. The isolates were exposed to broth at pH 3 or with 0.3% bile salt as basic screening conditions, and viable counts in three tubes per isolate were determined at 0, 2, and 4 hours and analyzed by two-way repeated-measures analysis of variance. Of fifteen colonies, five produced clear zones, and three were Gram-positive, catalase-negative presumptive lactic acid bacteria. At pH 3, relative viability was 86.10–90.15% after 2 hours, and counts exceeded the initial level after 4 hours (111.23–122.20%), possibly reflecting recovery or residual growth. In 0.3% bile salt, relative viability after 4 hours was 74.53–99.20%, and all reductions were below one logarithmic cycle. Isolate, time, and their interaction significantly affected counts in the acid assay, but only isolate did so in the bile salt assay. These isolates show preliminary probiotic-associated stress tolerance, and tamarind pulp may be a source of non-dairy probiotic candidates, although molecular identification and further functional and safety evaluations are required.