TAILIEUCHUNG - Báo cáo khoa học: Contribution of exofacial thiol groups in the reducing activity of Lactococcus lactis

Lactococcus lactiscan decrease the redox potential at pH 7 (Eh7) from 200 to )200 mV in oxygen free Man–Rogosa–Sharpe media. Neither the con-sumption of oxidizing compounds or the release of reducing compounds during lactic acid fermentation were involved in the decrease inEh7by the bacteria. | Contribution of exofacial thiol groups in the reducing activity of Lactococcus lactis D. Michelon1 S. Abraham1 B. Ebel1 J. De Coninck1 F. Husson1 G. Feron2 P. Gervais1 and R. Cachon1 1 Laboratoire de Genie des Precedes Microbiologiques et Alimentaires AgroSup Dijon Universite de Bourgogne Dijon France 2 Unite Mixte de Recherche 1129 FLAVIC ENESAD-INRA-UB Dijon France Keywords Lactococcus lactis proton motive force redox reducing activity thiol groups Correspondence R. Cachon Laboratoire de Genie des Precedes Microbiologiques et Alimentaires AgroSup Dijon Universite de Bourgogne site INRA 17 Rue Sully 21065 Dijon France Fax 33 3 80 69 32 29 Tel 33 3 80 69 33 73 E-mail Received 17 July 2009 revised 22 February 2010 accepted 8 March 2010 doi Lactococcus lactis can decrease the redox potential at pH 7 Eh from 200 to -200 mV in oxygen free Man-Rogosa-Sharpe media. Neither the consumption of oxidizing compounds or the release of reducing compounds during lactic acid fermentation were involved in the decrease in Eh7 by the bacteria. Thiol groups located on the bacterial cell surface appear to be the main components that are able to establish a greater exchange current between the Pt electrode and the bacteria. After the final Eh7 -200 mV was reached only thiol-reactive reagents could restore the initial Eh7 value. Inhibition of the proton motive force showed no effect on maintaining the final Eh7 value. These results suggest that maintaining the exofacial thiol -SH groups in a reduced state does not depend on an active mechanism. Thiol groups appear to be displayed by membrane proteins or cell wallbound proteins and may participate in protecting cells against oxidative stress. Introduction Electrochemical measurement of the oxidoreduction potential Eh in liquid media has been used for eight decades 1 . Recent studies have emphasized that the characterization of redox conditions is of both scientific and practical

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