Influence of environmental parameters on production of the acrolein precursor 3-hydroxypropionaldehyde by Lactobacillus reuteri DSMZ 20016 and its accumulation by wine lactobacilli Rolene Bauer a, ⁎, Maret du Toit b , Jens Kossmann a a Institute for Plant Biotechnology, Genetics Department, Stellenbosch University, Matieland 7602, Stellenbosch, South Africa b Institute for Wine Biotechnology, Department of Viticulture and Enology, Stellenbosch University, Matieland 7602, Stellenbosh, South Africa abstract article info Article history: Received 25 June 2009 Received in revised form 15 September 2009 Accepted 14 October 2009 Keywords: Acrolein 3-HPA Lactobacillus Wine Lactic acid bacteria belonging to the genus Lactobacillus are known to convert glycerol into 3-hydroxypropio- naldehyde (3-HPA) during anaerobic glycerol fermentation. Wine quality can be gravely compromised by the accumulation of 3-HPA, due to its spontaneous conversion to acrolein under wine making conditions. Acrolein is not only a dangerous substance for the living cell, but has been implicated in the development of unpleasant bitterness in beverages. This study evaluates the effect of individual environmental parameters on 3-HPA production by Lactobacillus reuteri DSMZ 20016, which only proved possible under conditions that allow accumulation well below the threshold concentration affecting cell viability. 3-HPA production was optimal at pH 6 and in the presence of 300 mM glycerol. Production increased with an increase in cell concentration up to an OD 600 of 50, whereas higher cell concentrations inhibited accumulation. Data presented in this study suggest that 3-HPA plays a role in regulating its own production through quorum sensing. Glycerol dehydratase possessing bacterial strains isolated from South African red wine, L. pentosus and L. brevis, tested positive for 3-HPA accumulation. 3-HPA is normally intracellularly reduced to 1,3-propanediol. This is the first study demonstrating the ability of wine lactobacilli to accumulate 3-HPA in the fermentation media. Recommendations are made on preventing the formation of acrolein and its precursor 3-HPA in wine. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Axelsson et al. (1987) first reported broad-spectrum antimicrobial action of 3-hydroxypropionaldehyde (3-HPA) produced by Lactobacil- lus reuteri. This compound was protected by patent in 1988 under the name reuterin and is proposed to be largely responsible for the probiotic effects of L. reuteri (Talarico et al., 1988). Probiotics are live microbial feed supplements which when administered in adequate amounts confer a health benefit on the host (WHO, 2002). Hence, L. reuteri is applied as a probiotic in the health care of humans and animals, while the food industry has started industrial applications with L. reuteri to enhance the quality and value of milk products and is using reuterin as a food preservative. Lactic acid bacteria (LAB) belonging to the genus Lactobacillus are known to convert glycerol into 3-HPA by a coenzyme B12-dependent glycerol dehydratase (EC 4.2.1.30) or its isoenzyme diol dehydratase (EC 4.2.1.29) (Smiley and Sobolov, 1962; Toraya et al., 1976). 3-HPA is normally an intracellular intermediate that does not accumulate, but is reduced to 1,3-propanediol (1,3-PDO) by a NADH- linked dehydrogenase (1,3-PD oxidoreductase; EC 1.1.1.202). Only a few lactobacilli strains have been identified with the ability to accumulate 3-HPA extracellularly (Garai-Ibabe et al., 2008; Martin et al., 2005; Pasteris and Strasser de Saad, 2009; Sauvageot et al., 2000). 3-HPA is a valuable compound that serves as a precursor for chemicals such as acrolein, acrylic acid, 1,3-PDO, and polymers (Vollenweider and Lacroix, 2004). Production is generally achieved through traditional chemistry from petrochemical resources as a dehydration product of glycerol. Due to increasing public demand for environmentally friendly products, recent studies aimed at optimizing bacterial 3-HPA produc- tion (Doleyres et al., 2005; Zamudio-Jaramillo et al., 2008). 3-HPA is a precursor to acrolein which is spontaneously produced through the secession of H 2 O under conditions of low acidity and/or heat. Acrolein, being a highly reactive α,β-unsaturated aldehyde, is a pulmonary toxicant and an irritant of mucous membranes that is con- sidered by regulatory agencies to be one of the greatest non-cancer health risks (ORL-RBT LD50 = 7 mg kg -1 ; ORL-RAT LD50 = 46 mg kg -1 ) (Esterbauer et al., 1991; Seaman et al., 2006). Acrolein is very polar and highly soluble in water and organic solvents, such as ethanol. Since analytical detection of acrolein in alcoholic water solution is complicated, few studies evaluated its content in beverages (Bauer et al., in review-b). Its presence has however been reported in fermented foodstuffs, such as International Journal of Food Microbiology 137 (2010) 28–31 ⁎ Corresponding author. Current address: Institute for Microbial Biotechnology and Metagenomics, Department of Biotechnology, University of the Western Cape, Private Bag X17, Bellville, 7535 Cape Town, South Africa. Tel.: +27 21 959 2817; fax: +27 21 959 3505. E-mail address: rbauer@uwc.ac.za (R. Bauer). 0168-1605/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ijfoodmicro.2009.10.012 Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro