Inhibitory effect of casein and alpha-lactalbumin on Chryseobacteria spp. isolated from milk and dairy products

Abstract

In this study, pathogenic and food spoilage bacteria Chryseobacteria spp. were isolated by a new method from 150 samples of raw milk (26/50), heat-treated milk (HTM) (5/50) and butter (2/50). The species with the highest prevalence was C. indologenes (10.67%) followed by C. bovis and C. gleum (4.67% each), and C. bernardetii (2%). The three new strains C. bernardetii, C. gleum, and C. indologenes were named MW703610, MW703611, and MW703612, respectively, with identities ranging from 97.8% to 98.9%. Gene sequencing was performed on some isolates and proved the highest sequence similarity for C. bernardetii WD1 (97.8%), C. gleum WD2 (98.9%) and C. indologenes WD3 (98.9%). Most of the isolated Chryseobacteria spp. showed proteolytic and lipolytic activity. Therefore, casein and alpha-lactalbumin were used as natural antibacterial substances against all isolates. Higher bioactivity against the isolates was obtained using casein rather than the alpha-lactalbumin. Based on these results, casein and alpha-lactalbumin may be promising natural bioactive agents against pathogenic Chryseobacteria spp. Further studies should be done to establish the natural peptide fractions associated with the observed activity.