14A-30

I. SURJAWAN and C. L. HICKS. University of Kentucky, Lexington, KY 40546-0215

a-lactalbumin (AL) is a metallo-protein that has a primary calcium binding site which is required for its structural integrity. Calcium is a requirement for the replication of some lactococcal phages and required for efficient adsorption of phage (F) c2 to the host cell. Lactococcal F proliferation which causes problems in cheese fermentations may be inhibited by regulating Ca²⁺ in milk. A low level of AL in milk has not shown an inhibitory effect against F proliferation. In this study, M17 medium with and without AL added as Ca²⁺ binder was inoculated with L. lactis ssp lactis C2 culture with and without being infected with Fc2. Growth and lysis of C2 host culture was monitored spectrophotometrically at l 600 nm. AL was added at 0.5 and 1% (w/v) to M17 medium containing 10mM Ca²⁺. When a 1% concentration of AL was added to the growth medium, a slight inhibition of the C2 culture was observed. When the host culture (C2) was infected (at 15 min) with Fc2 (10⁶ pfu/ml), lysis was delayed by 30 min and 75 min in the medium containing 0.5% and 1% AL, respectively. Further test were conducted by adding 0.75 % (w/v) heat-treated (65^oC; 30min) AL to an M17, inoculated with C2 host, and infected with 10⁴, 10⁵, 10⁶, and 10⁷ (pfu/ml) Fc2 titers. In the presence of AL, host cell lysis by Fc2 titers of 10⁷ to 10⁵ (pfu/ml) were delayed by 40 to 70 min and completely inhibited at Fc2 titer of 10⁴ (pfu/ml). These results suggest that AL bound Ca²⁺ in the medium and inhibited Fc2 proliferation. AL has approximately a 40% sequence homology and shares a common 3D fold with lysozyme. Thus, AL may also bind to glycosidic bond linkage between sugars without enzymatic activity. AL may form a mat across the cell surface blocking F tail attachment to host receptors.

Session 14A, Dairy Foods: General developments in dairy technology I
8:30 AM - 12:00 PM, Sunday AM

2003 IFT Annual Meeting - Chicago,