Background: Goat milk is reported to have antimicrobial activity of several pathogen bacteria that contained on food materials. The research related with antimicrobial activity of Alpha-S2 casein from goat milk is relatively less than other casein components. Herein, we reported the antimicrobial activity of caprine Alpha-S2 Casein (CSN1S2) protein from Ethawah breed goat milk and yoghurt in Gram positive (Listeria monocytogenes, Staphylococcus aureus and Bacillus cereus) and negative pathogen bacteria (Escherichia coli, Salmonella typhi and Shigella flexneri). Those bacteria were known as pathogens that caused gastrointestinal infection. Methods: Serial dilution and agar diffusion analysis with three different concentrations of caprine CSN1S2, 1.25 mg/ml, 2.5 mg/ml, and 5 mg/ml were used to test the inhibition effect of protein on the viability of bacteria cells. The inhibitory activity of caprine CSN1S2 was based on dose dependent manner. Agar diffusion analysis was showed the larger diameter of clear zone at B. cereus and S. flexneri. Results: The serial dilution analysis was shown the inhibition of almost in all groups of bacteria with concentration 5 mg/ml higher by CSN1S2 protein of goat fresh milk than yogurt. The inhibitory activity caprine CSN1S2 protein of fresh milk was shown a vary inhibition clear zone with optimal concentration 5 mg/ml, however CSN1S2 protein of goat yogurt intermediate effectively was only in gram negative bacteria. The weakness bacteria against inhibition activity caprine CSN1S2 protein was B. cereus (Gram positive) and S. flexneri (Gram negative). Meanwhile the strongest bacteria against inhibition activity caprine CSN1S2 protein was S. typhi (Gram negative), may cause in this bacteria has lipopolysaccharide prevent to interact with that protein as proper. Conclusion: This study result concluded that the caprine CSN1S2 protein has inhibition activity in opposition to pathogenic bacteria by optimal concentration 5 mg/ml in all bacteria and indicated caprine CSN1S2 protein as anti-microbial agent.
Antimicrobial, CSN1S2, Ethawah goat, milk, pathogen bacteria