Studies on the Effects of End Product Inhibition over Lactic Acid Bacteria under High Cell Density Cultivation Process

Author(s): G. Sreekumar, Soundarajan Krishnan and R. Christabel Prathipa

Lactic acid bacteria (LAB) have recently caught the rapt attention of medical and scientific researchers as they form the part of gut microflora and affect the host beneficially as probiotic organisms. Lactic acid is the major metabolic end-product of LAB culture through carbohydrate fermentation, which finds its potential use in food, chemical & pharmaceutical industry. Reduced biomass concentration is the major bottle- neck in the use of LAB culture for the production of lactic acid due to end product inhibition. It becomes inevitable to search an alternate fermentation process towards attaining high levels of biomass accumulation. Two strains of Lactic acid bacteria namely Lactococcus lactis, Lactobacillus reuteri, had been employed for the production of lactic acid. The growth kinetic parameters such as specific growth rate, doubling time, oxygen requirement, substrate utilization profile and yield coefficient with respect to biomass formation were determined under optimal cultivation conditions. These cultures were experimented towards high cell density cultivation process which yielded a remarkable increase in the product as well as better viability of the cell. By employing the total cell retention culture technique the biomass concentration has been found increased up to 50.19%, 51.75% respectively. On these test cultures, the effects of lactic acid inhibition in terms of the minimum inhibitory concentrations, bacteriostatic and bacteriocidal concentrations were also been determined. An overall decrease in viability and significant changes in the morphological structures concludes that L. reuteri is less susceptible than L. lactis. The attempts towards strain improvement and effect of bio-parameters on lactic acid tolerance are currently under investigation. Based on this improved alternate process, the Lactic acid bacterial cultures can be well employed for important industrial purposes as this work provides a scope for overcoming the product inhibition effects

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