Submitted to: Current Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/18/2007
Publication Date: 7/31/2007
Citation: Somkuti, G.A., Gilbreth, S.E. 2007. Influence of organic buffers on bacteriocin production by streptococcus thermophilus st110. Current Microbiology. 55(2):173-177. Interpretive Summary: Pediococci are microbes frequently associated with spoilage in wine and beer fermentations. The control of these unwanted lactic spoilage bacteria may be possible with bacteriocins which are natural antimicrobials produced by related dairy fermentation bacteria used in yogurt production. Thermophilin 110 is a new type of bacteriocin found in a yogurt culture that controls pediococci by inducing cell lysis which results in cell death. The production of thermophilin 110 by the yogurt culture was evaluated in growth media formulated from whey permeate which was prepared from the effluent of cheese manufacture. The results showed that the relatively inexpensive dairy whey permeate supplemented with yeast extract and appropriate buffering salts supported the growth of the yogurt culture and was suitable for producing this natural antimicrobial agent in large amounts which would be needed for applications to control spoilage-causing pediococci in industrial wine and beer fermentations.
Technical Abstract: The effect of the organic buffer salts MES, MOPS and PIPES on the growth of S. thermophilus ST110, medium pH and accumulation of the antipediococcal bacteriocin thermophilin 110 were evaluated in whey permeate media over a period of 24 h. In non buffered medium, thermophilin 110 production at 37°C paralleled the growth of S. thermophilus ST110 and reached a maximum after 8-10 h. Addition of organic buffer salts decreased the drop in medium pH and resulted in increased biomass (dry cells, 'g/ml) and higher yields of thermophilin 110 (units/'g of cells). The best results were obtained by the addition of 1% (w/v) MES to the medium which reduced pH drop to 1.8 units after 10 h of growth (compared to 2.3 pH units in the control), and resulted in a 1.5-fold increase in cell mass (495 'g/ml) and a 7-fold increase in thermophilin 110 yield (77 units/'g of dry cells) over the control. The results showed that whey-permeate based media may be suitable for producing large amounts of thermophilin 110 needed for controlling spoilage pediococci in industrial wine and beer fermentations.