Quantification of Antimicrobial Compounds Produced by Lactic Acid Bacteria Isolated from Pulses
Bashipangu Gouthami
Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India.
A. Ramalakshmi *
Department of Food Process Engineering, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India.
M. Balakrishnan
Department of Food Process Engineering, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India.
S. Karthikeyan
Post Harvest Technology Centre, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India.
V. Paranidharan
Department of Plant Pathology, Tamil Nadu Agricultural University Coimbatore-641003, Tamil Nadu, India.
*Author to whom correspondence should be addressed.
Abstract
In this study, 11 LAB isolates were isolated from the pulses (green gram and black gram) were tested for biochemical characteristics (catalase, MR-VP, citrate utilization, nitrate reduction) based on these tests four isolates were evaluated for their antimicrobial activity against three prominent pathogens: Escherichia coli, Pseudomonas aeruginosa, and Aspergillus flavus NRRL3357 under different pH 9 (5.5, 6.5, 7.5 and 8.5) and temperature (17ºC, 27ºC, and 40ºC). Among the four isolates, one isolate LB4 exhibited notable antimicrobial efficacy against all three pathogens under pH (6.5) 8.1± 0.6 mm, 8.3 ± 0.5 mm, and 6.6 ± 0.8 mm respectively. Optimum antimicrobial activity showed at temperature 27º against same pathogens the zone of inhibition mean values 10± 0.9 mm, 5.0± 0.6 mm, 8.3± 1.2 mm respectively. LB4 isolate was tested for quantification of key metabolites after three days of incubation, lactic acid, acetic acid, and hydrogen peroxide. Lactic acid (4.6 g/l) and acetic acid (4.8 g/l) were consistently produced in higher amounts, while hydrogen peroxide production remained relatively low (0.58 g/l) by the LB4 isolate. The results indicated the intricate relationship between antimicrobial activity, environmental factors, and metabolite production, emphasizing the promising role of this isolate in combating microbial infections under diverse conditions.
Keywords: Lactic acid bacteria, antimicrobial compounds, pathogens, antimicrobial activities