THERMOPHILIN 110:A BACTERIOCIN OF STREPTOCOCCUS THERMOPHILUS ST110

Authors: Gilbreth, Stefanie; Somkuti, George

Submitted to: Current Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2005
Publication Date: 9/1/2005
Citation: Gilbreth, S.E., Somkuti, G.A. 2005. Thermophilin 110:a bacteriocin of streptococcus thermophilus st110. Current Microbiology.

Interpretive Summary: Specific cultures of lactic acid bacteria are essential in the fermentation of cheeses, yogurt and meat products but their presence may create spoilage problems for the wine and beer industries. Control of unwanted lactic spoilage bacteria such as pediococci in wine and beer fermentations may be possible with bacteriocins which are antibacterial agents produced by related lactic acid bacteria. As a group, lactic acid bacteria used in yogurt production have not been studied extensively as a source of such natural preservatives. The evaluation of a group of Streptococcus thermophilus strains for bacteriocin production resulted in the discovery of thermophilin 110, an apparently new type of bacteriocin with unique properties. Thermophilin 110 was shown to have two peptide components and a small amount of carbohydrate and it lost its activity when exposed to protein digesting enzymes. Thermophilin 110 apparently inhibited pediococci by inducing cell lysis which resulted in cell death. The effectiveness of thermophilin 110 against pediococci may permit its utilization as a biopreservative to control the growth of these spoilage bacteria in wine and beer fermentations.

Technical Abstract: A screen of thermophilic lactic acid bacteria identified Streptococcus thermophilus strain ST110 as the putative producer of a bacteriocin with high level of activity against pediococci. Thermophilin 110 was isolated from culture supernatant after 16 h of growth and partially purified by a chloroform extraction procedure. The bacteriocin inhibited the growth of several lactic acid bacteria and in the case of Pediococcus acidilactici cultures, it induced cell lysis with the concomitant release of OD260 - absorbing material and intracellular enzymes. SDS-PAGE analysis revealed two components with estimated sizes between 4.0 kDa and 4.5 kDa, respectively, with possible involvement in bacteriocin activity as indicated by agar overlay assays with P. acidilactici as the target organism. Thermophilin 110 was inactivated by several proteolytic enzymes and also by amylase which indicated the putative requirement of a glycosidic component for activity. The bacteriocin produced by S. thermophilus may be especially useful in the food processing industries to control spoilage caused by pediococci.