Inhibition of Lactobacillus Growth by Amino Acids and Phytochemicals in the Fermentation of Curd by Disc Diffusion Method

Lactic acid bacteria have been widely used for the fermentation of milk and its products. In this study we have investigated the role of amino acids and phytochemicals on the curdling process. The objective was whether the curdling process could be inhibited/enhanced by the introduction of these compounds so that it could be preserved for a longer time or curdling period could be shortened. The inhibition of Lactobacillus growth by amino acids and phytochemicals were studied in Deman, Rogosa and Sharp (MRS) medium. The cell suspension was aseptically spread into MRS plates. Discs were charged separately with varying concentrations (250 ppm, 500 ppm, 1000 ppm) of 20 amino acids and 10 phytochemicals. Plates were observed for the formation of 'zone of inhibition'. The test organism showed sensitivity to alanine, leucine, valine, glutamic acid and monosodium glutamate and two phytochemicals, namely protocatechuic acid and syringic acid. All these compounds showed positive results by inhibiting the curdling process. Thus, the present study shows that Lactobacillus growth could be inhibited by amino acids and certain phytochemicals and control the fermentation process.