Effect of purple sweet potato levels (Ipomoea batatas L.) carbohydrate sources on fermentation kinetics and lactic acid production by Lactobacillus paracasei

This research aims to determine the effect of purple sweet potato extract level as a carbohydrate source substrate on the kinetics of fermentation and lactic acid production by Lactobacillus paracasei. Research using L. paracasei, which is a lactic acid bacteria (LAB) collection of the Laboratory of Nutrition Biochemistry of the Faculty of Animal Sciences UGM. Fermentation kinetics were observed with a graph of substrate degradation derived from the Michaelis-Menten equation. Purple sweet potato extract concentration (S) used to determine the value of Km and qmax of L. paracasei was 0,01; 0,05 and 0,1. Purple sweet potato extract concentration (S), which was used for observing the kinetics fermentation and lactic acid production, was 1/2 Km, Km and 1,5 Km. Observation of substrate degradation was known by conducting the Antrone test. The results of the fermentation kinetics test in the form of slope values, as a parameter of the speed of substrate degradation L. paracasei. Lactic acid production was measured using the Barker and Summerson methods. Analysis data for the value of Km and qmax observed descriptively. While, the data of the fermentation kinetics test, pH values and production of lactic acid were analyzed using analysis of variance with a Completely Randomized Design (CRD) in a unidirectional pattern. The addition of purple sweet potato extract to liquid fermentation L. paracasei grading 1,5 Km (3 g/100ml) has shown the optimum pH value and lactic acid production but 1/2 Km concentration shows higher substrate efficiency.