The Ks and µmax Determination of Proteolytic Lactic Acid Bacteria Isolated from Colostrum of Dairy Cattle with Differences in Energy Source Levels

This study determines the optimal substrate-level used by proteolytic acid lactic bacteria to produce a product expressed in substrate affinity constant (Ks). Proteolytic lactic acid bacteria were isolated from cow colostrum, carried out at the Laboratory of Nutritional Biochemistry, Faculty of Animal Science, Universitas Gadjah Mada. Proteolytic lactic acid bacteria was rejuvenated first in a solid medium, and the amount is multiplied in MRS broth medium to be used as stock. Proteolytic lactic acid bacteria was observed for growth on a defined medium with five variations of glucose substrate levels. The glucose levels were given at 0.15%, 0.1%, 0.05%, 0.01%, and 0% with three replications and one negative control at each level. Proteolytic lactic acid bacteria were incubated at 37°C for 24 hours. Observations were made every two hours. The results of the absorbance observations were used to calculate the Ks value. The Ks value was used to determine the substrate level in the next liquid fermentation. The Ks and µmax values obtained in the proteolytic lactic acid bacteria were 0.0569 gram/100 ml and 0.0125 per hour, respectively.