Journal of Molecular Catalysis B: Enzymatic 39 (2006) 179–183 Effect of redox potential on the growth of Yarrowia lipolytica and the biosynthesis and activity of heterologous hydroperoxide lyase Florence Husson a,∗ , Viet Phu Tu a , Mirna Santiago-Gomez a , R´ emy Cachon a , Gilles Feron a , Jean-Marc Nicaud b , S´ elim Kermasha c , Jean-Marc Belin a a Laboratoire de Microbiologie, UMR UB/INRA 1232, ENSBANA, 1, Esplanade Erasme, Campus Universitaire Montmuzard, 21000 Dijon, France b Laboratoire de Microbiologie et G´ en´ etique Mol´ eculaire, INRA-CNRS-INAPG UMR 2585, BP 01, 78 850 Thiverval-Grignon, France c Department of Food Science and Agricultural Chemistry, McGill University, 21,111 Lakeshore, Ste-Anne de Bellevue, Que., Canada H9X 3V9 Available online 10 March 2006 Abstract The aim of this study was to investigate the effect of redox potential (Eh) on the growth of the yeast Yarrowia lipolytica in both oxidizing (Eh = +350 mV) and reducing (Eh = -150 mV) media and its effect on the expression and activity of hydroperoxide lyase (HPL). HPL activity was assayed in media with Eh values ranging from -250 to +720mV. In order to change the Eh value of the media, reducing agents including dithiotreitol (1 g/L) and hydrogen (4%) as well as oxidants such as potassium ferricyanide (1 g/L) and oxygen (100%), were used. The experimental findings showed that oxidizing conditions, with Eh of +350mV, were favorable for the growth of the yeast, whereas reducing conditions, with Eh values of -150mV, resulted in a higher expression of HPL. In addition, the results showed that the enzymatic activity of the purified HPL was enhanced in the presence of 0.5 mM dithiotreitol but decreased with 1 mM potassium ferricyanide and bubbling O 2 . However, HPL activity increased 1.5 times in the presence of 4% hydrogen with an Eh value of -170 mV. © 2006 Elsevier B.V. All rights reserved. Keywords: Yarrowia lipolytica; Culture medium; Oxido-reduction potential (ORP); Hydroperoxide lyase activity 1. Introduction Hydroperoxide lyase (HPL) is an enzyme widely distributed in plants and involved in the biosynthesis of volatile aldehy- des and -oxo-acids, obtained by cleavage of the C C bond between the hydroperoxide (HP) group and neighboring dou- ble bond of HPs of polyunsaturated fatty acids (PUFAs), such as linoleic acid [1]. Aldehydes (C6 and C9) as well as their corresponding alcohols, obtained from the HPL bioconversion of 13- and 9-HPs of linoleic and linolenic acids, respectively, are important constituents of the characteristic flavors of fruits, vegetables and green leaves [2]. These flavoring compounds are molecules of higher added-value, widely used in the aroma industry. Previous work by our group [3] showed that the chloroplast fraction and purified HPL from green bell pepper were of partic- ∗ Corresponding author. Tel.: +33 3 80 39 66 80; fax: +33 3 80 39 66 41. E-mail address: florence.husson@u-bourgogne.fr (F. Husson). ular interest for the production of green note molecules, such as hexanal and trans-2-hexenal. However, the amount of enzyme recovered was limited, making the cost of biocatalyst production too high to be considered for an industrial application. Subsequent research work carried out by our group [4] was aimed at the genetic expression of HPL from green bell pep- per in the yeast Yarrowia lipolytica. The HPL activity from the yeast extract as well as the whole yeast cells was measured to be 1200 enzyme U/L culture medium. In addition, the amount of C6-aldehydes produced directly in the culture medium, after addition of the HP substrates, was relatively high (350 mg/L reaction medium). A process using whole S. cerevisiae cells transformed with banana HPL was previously developed to pro- duce cis-3-hexenal and cis-3-hexenol [5]. The literature reported that micro-organisms were sensitive to the oxido-reduction potential (ORP) of the culture medium [6]. The ORP has also been called the redox potential (Eh) and is a physicochemical parameter that determines the oxidizing or reducing properties of the medium. Eh depends essentially upon the composition of the medium in terms of the properties 1381-1177/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molcatb.2006.01.021