Research Article: Biotransformation of caffeoyl quinic acids from green coffee extracts by Lactobacillus johnsonii NCC 533

Date Published: May 21, 2013

Publisher: Springer

Author(s): Rachid Bel-Rhlid, Dinesh Thapa, Karin Kraehenbuehl, Carl Erik Hansen, Lutz Fischer.

http://doi.org/10.1186/2191-0855-3-28

Abstract

The potential of Lactobacillus johnsonii NCC 533 to metabolize chlorogenic acids from green coffee extract was investigated. Two enzymes, an esterase and a hydroxycinnamate decarboxylase (HCD), were involved in this biotransformation. The complete hydrolysis of 5-caffeoylquinic acid (5-CQA) into caffeic acid (CA) by L. johnsonii esterase occurred during the first 16 h of reaction time. No dihydrocaffeic acid was identified in the reaction mixture. The decarboxylation of CA into 4-vinylcatechol (4-VC) started only when the maximum concentration of CA was reached (10 μmol/ml). CA was completely transformed into 4-VC after 48 h of incubation. No 4-vinylphenol or other derivatives could be identified in the reaction media. In this study we demonstrate the capability of L. johnsonii to transform chlorogenic acids from green coffee extract into 4-VC in two steps one pot reaction. Thus, the enzymatic potential of certain lactobacilli might be explored to generate flavor compounds from plant polyphenols.

Partial Text

Polyphenols have been reported to exert a variety of biological activities, such as free radical scavenging, metal chelating and modulation of enzyme activity (
Sud’ina 1993
). The main classes of phenolic compounds are hydroxycinnamic acids such as caffeic acid (CA), ferulic acid (FA), and p-coumaric acid (PCA), mainly in esterified form with organic acids, sugars, and lipids. CA (Figure 1) is the major representative of hydroxycinnamic acids and occurs in foods essentially as ester with quinic acid (chlorogenic acids) (Figure 1). Although chlorogenic acids are common in vegetables, the largest amounts are present in coffee (
Clarke 1987
). These phenolic acids are toxic to some but not all microorganisms. Some Pseudomonas strains, as well as Acinetobacter calcoaceticus, are able to use them as the sole source of carbon for growth (
Overhage 1999
). Other studies have confirmed the ability of some lactic acid bacteria to metabolize p-coumaric acid into 4-vinylphenol (4-VP) (
Osborn 1997
(van Beek
). One of the mechanisms evolved by microorganisms to counteract phenolic acid toxicity is the induction of enzymes able to metabolize these compounds. Lactic acid bacteria, especially Lactobacillus plantarum2000
(Barthelmebs
), Pediococcus pentosaceus2000
(Barghini
) and Pseudomonas fluorescens1998
) are able to decarboxylate p-coumaric acid and ferulic acid into vinylphenol, vinylguaiacol and vanillic acid. The decarboxylation is catalyzed by a hydroxycinnamate decarboxylase (HCD). This enzyme was found to be produced by different groups of microorganisms including gram negative bacteria, gram positive bacteria and yeasts. Among the gram positive bacteria only lactic acid bacteria (
Rodriguez 2008
;
van Beek 2000
;
Landete 2007
) and some Bacillus species (
Torres y Torres 2001
;
Degrassi 1995
;
Cavin 1998
;
Edlin 1998
) were identified to display HCD activity. This enzymatic activity might be constitutive or induced when the microorganisms are exposed to exogenous chemicals (
Hashidoko 2001
). The constitutive expression of HCDs has been reported in yeasts and some gram negative bacteria. The yeasts, Brettanomyces anomalus and B. bruxellensis, commonly found in wine, are responsible for the production of flavoring compounds such as 4-vinylphenol, 4- vinylguaiacol, 4-ethylphenol and 4-ethylguaiacol (
Edlin 1998
;
Godoy 2008
;
Morata 2013
) which are the catalytic products of cinnamic acids mediated by HCD. 4-Vinyl derivatives are considered to contribute to the smoky aroma of cured meat products (
Guillén 1998
). 4-VG and 4-VP have been approved as flavoring agents by regulatory agencies (Joint Expert Committee on Food Additives (
JECFA) 2001
). 4-Vinyl derivatives have also been reported as potent antioxidants (
Terpinc 2011
). The HCD activity has been reported in Lactobacillus species (
Rodriguez 20082008
;
van Beek 2000
;
Landete 2007
) but not yet in L. johnsonii. In a previous study we demonstrated the ability of L. johnsonii to hydrolyze rosmarinic acid into caffeic and 3,4-dihydroxyphenyllactic acids (
Bel-Rhlid 2009
). In the present study, we investigated the in vitro incubation of green coffee extract with L. johnsonii to hydrolyze chlorogenic acids into corresponding hydroxycinnamic acids. These phenolic compounds could be then transformed into corresponding vinylphenols by decarboxylase activity.

Chlorogenenic acids (CQA) are found in wide range of vegetables and fruits and are particularly abundant in green coffee (6 – 10% dry basis) (
Clarke 1987
). Roasting of green coffee beans reduces the amount of chlorogenic acids (2.5-4.0%) (
Debry 1994
) and hypothetical chemical degradation pathway has been proposed (
Franck 2007
;
Müller 2007
). On the other hand, intestinal microorganisms (
Couteau 2001
;
Monteiro 2007
) and other lactic acid bacteria (
Guglielmetti 2008
) were shown to be able to transform chlorogenic acids into caffeic and quinic acids by cinnamoyl esterase. Several other studies reported on the decarboxylation of hydroxycinnamic acids (e.g. caffeic acid, ferulic acid) into vinyl phenols by bacteria and yeasts (
Plumb 1999
;
Huang 1994
;
Hashidoko 2001
;
Rodriguez 2008
;
Curiel 2010
). However, to our knowledge, this is the first study reporting on two step, one pot bioconversion of caffeoyl quinic acids into 4-VC by the same microorganism (Figure 1). Our study reveals that L. johnsonii NCC 533 exhibits a chlorogenate esterase and a hydroxycinnamate decarboxylase like activities when incubated with green coffee extract for 24 h at 37°C. The chlorogenate esterase from L. johnsonii was already identified, cloned, and characterized (
Bel-Rhlid 2009
;
Kim 2009
). This enzyme showed high affinity and catalytic efficiency toward aromatic compounds such as chlorogenic acids. HCD has never been reported in L. johnsonii NCC 533. To explore both enzymatic activities synergistically, L. johnsonii was used as whole cell and it was incubated with GCE in a one pot reaction system. The formation kinetics of CA and 4-VC were studied under different reaction conditions. The first reaction, hydrolysis of chlorogenic acids into CA, started quickly, and the highest concentration of CA was generated after 16 h of incubation. After this level of CA was reached, the second reaction, decarboxylation of CA, was started, and after 28 h of reaction time a plateau was reached with maximum concentration of 4-VC. In the literature, the most frequently observed metabolic pathway of CA is by decarboxylation (
Landete 2007
;
Cavin 1997
;
de las Rivas 2009
) and further reduction to yield 4-ethylcatechol (
Peppercorn 1971
;
Landete 2007
). Alternatively, CA can be reduced to dihydrocaffeic acid which is then dehydroxylated into m-hydroxyphenylpropionic acid. In our study, neither 4-ethylcatechol nor dihydrocaffeic acid were identified in the reaction mixture. Similar results have been reported for Lactobacillus brevis strains (
Curiel 2010
).

The authors declare that they have no competing interests.

 

Source:

http://doi.org/10.1186/2191-0855-3-28

 

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