Lactic acid bacteria phenolic compounds

In recent years several applications of the HC1 proteolysis have been published in the field of Se speciation, for example, as regards Se-enriched lactic acid bacteria [66], mullet and cockles [8], and algae [67], where the technique provided extraction efficiencies of greater than 90 percent and preserved the integrity of the selenoamino acids. The general usefulness of this method of Se speciation is, however, questionable. Sometimes the authors do not state clearly whether phenol - an essential compound for the prevention of oxidation of SeCys - was used or not. In practice, neither phenol nor the short-duration MW-assisted irradiation can prevent the alteration of selenoamino acids [68-71], At the moment, no final conclusion on the applicability of HC1 proteolysis can be drawn, as CRMs certified for SeCys are still unavailable. On the other hand, an Se extraction efficiency of 80-90 percent can be achieved with this method only if either proteins are at least partly separated from the other components of the matrix, for example, separate analysis of fish muscles is carried out [8], or a considerable portion of Se is originally contained in inorganic forms in the sample, as observed by B Hymer and Caruso [1] in the case of Se-enriched food supplements. 

Volatile phenols originate from hydroxycinnamic acids (ferulic, p-coumaric, or caffeic acid) by the action of hydroxycinnamate decarboxylase enzyme, which turn the hydroxycinnamics acid into vinylphe-nols (Albagnac, 1975 Grando et al., 1993). Then, these compounds are reduced to ethyl derivatives by vinylphenol reductase enzymes characteristic of species, such as Dekkera bruxellensis, Dekkera anomala, Pichia guillermondii, Candida versatilis, Candida halophila, and Candida mannitofaciens (Edlin et al., 1995 1998 Dias et al., 2003 Chatonnet et al., 1992 1995 1997 Dias et al., 2003), apart from very small quantities produced by some yeasts and lactic acid bacteria under peculiar growth conditions (Chatonnet et al., 1995 Barata et al., 2006 ... 

The action of phenolic compounds on lactic acid bacteria growth remains relatively nnknown. Past results have shown that polyphenols tested alone or in a mixture had an inhibitory effect. Saraiva (1983) noticed, on the contrary, that gallic acid stimulates yeasts and lactic acid bacteria. Conversely, different phenolic acids (coumaric, pro-tocatechic acid, etc.) and condensed anthocyanins inhibited them. Enological tannins were found to have an antibacterial effect (Ribdreau-Gayon et al 1975). The effect of phenolic compounds on lactic acid bacteria growth remains unclear. 

Silva, L, Campos, F.M., Hogg, T, and Couto, J.A. (2011) Wine phenolic compounds influence the production of volatile phenols by wine-related lactic acid bacteria. 7 App/ Microbiol 111, 360-370. 

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