Biochemical Engineering Journal 55 (2011) 176–184 Contents lists available at ScienceDirect Biochemical Engineering Journal j o ur nal homep a ge: www.elsevier.com/locate/bej Development of a reversible binding process for in situ removal of 3-hydroxypropionaldehyde during biotechnological conversion of glycerol D.P. Rütti, C. Lacroix ∗ , T. Jeremic ¸ , M. Mathis, A. Díe, S. Vollenweider 1 Laboratory of Food Biotechnology, Institute of Food Science and Nutrition, ETH Zurich, CH-8092 Zurich, Switzerland a r t i c l e i n f o Article history: Received 2 October 2010 Received in revised form 17 March 2011 Accepted 6 April 2011 Available online 13 April 2011 Keywords: Reuterin Biotransformation Bisulfite ISPR Antimicrobial Platform chemical a b s t r a c t 3-Hydroxypropionaldehyde (3-HPA) has a great potential in the pharmaceutical-, food-, and chemical industry as a potent antimicrobial compound and chemical precursor. Until now it is not commercially available, occurring only as intermediate in production of petro-derived 1,3-propanediol. In this study, we developed a new method for 3-HPA isolation, biotechnologically produced by Lactobacillus reuteri. A composition of an Amberlite anion exchange resin and hydrogensulfite (IRA-SO 3 H) was generated to extract 3-HPA from the complex mixture of the production medium. 3-HPA was successfully recovered and concentrated in a pure form. Using this approach, IRA-SO 3 H was evaluated to bind 3-HPA through- out the bioconversion. The IRA-SO 3 H successfully bound already produced 3-HPA without decreasing L. reuteri viability. However, new 3-HPA formation was repressed. To conclude, our data showed for the first time the selective extraction of 3-HPA from the bioconversion medium and its subsequent recovery. Future work is needed to adapt this system to an in situ product removal process not interfering with the bioconversion. © 2011 Elsevier B.V. All rights reserved. 1. Introduction 3-Hydroxypropionaldehyde (3-HPA) can be produced biotech- nologically from glycerol using Lactobacillus reuteri [1]. After release into the aqueous medium it forms an equilibrium (HPA system or 3-HPA) with its hydrate and its dimer reuterin [2,3]. 3-HPA inhibits the growth of bacteria, moulds, yeasts, and protozoa including human pathogenic and food spoilage organisms [3,4] making it interesting for use as an antimicrobial in the health-care- and food industry. As a precursor for the synthesis of 1,3-propanediol (1,3- PDO), acrolein, hydroxypropionic acid, or acrylic acid, 3-HPA has also great potential for the chemical industry [5]. Commercialisation is desired but needs large-scale production of clean 3-HPA. Purification of 3-HPA, formed during the production of petro-derived 1,3-propanediol is not feasible [5]. Biotechnologi- cal conversion of low cost glycerol, using bacteria as biocatalyst is a promising approach. As previously reviewed, bacteria of six genera were able to convert glycerol into 3-HPA [5]. Out of these, the probi- otic Lactobacillus reuteri (L. reuteri) yielded highest amounts of free 3-HPA (235 ± 3 mM [1]) using a two-step process where viable cells ∗ Corresponding author at: ETH Zurich, Institute of Food Science and Nutrition Schmelzbergstrasse 7, CH-8092 Zurich, Switzerland. Tel.: +41 44 632 53 67; fax: +41 44 632 14 03. E-mail address: christophe.lacroix@ilw.agrl.ethz.ch (C. Lacroix). 1 Present address: Givaudan Dübendorf AG, Überlandstrasse 138, 8600 CH- Dübendorf/ZH, Switzerland. were incubated after growth in 400 mM glycerol solution [1,6,7]. Responsible for the high 3-HPA production of L. reuteri is the unique combination of the propanediol utilisation (pdu) operon, and the pseudovitamin B 12 -operon [8–10]. The pdu- and B 12 -operon in L. reuteri form a genomic island (a cluster of genes that is not found in closely related organisms and has divergent features compared to other gene clusters on the chromosome), which is proposed to be important in the evolution of health promoting strains in the human gut [11]. However, accumulation of aldehydes such as 3-HPA is lim- ited by the cell toxicity of these products [12]. The minimum inhibitory concentration (MIC) and minimum bactericidal concen- tration (MBC) of 3-HPA for L. reuteri were determined to be in the range of 30–50 mM and 60–120 mM 3-HPA, respectively [13], cor- responding to 3-HPA concentrations inducing cell death during its production with the same organism [1,5]. Consequently, to cell inactivation and cell death, 3-HPA production stops and cells can- not be reused for additional production cycles. An economical and large scale process, however, needs high concentrations of viable cells, which could be reused. One possible solution is the in situ removal of the aldehyde dur- ing production [14,15]. The in situ product removal (ISPR) of 3-HPA was successfully achieved using semicarbazide, resulting in very high production of 621 mM 3-HPA-semicarbazone from 761 mM glycerol in small scale experiments with Klebsiella pneumoniae [16]. Although these results are promising, the recovery of 3-HPA from the semicarbazone was neither reported [5,16–18], nor successfully performed in our laboratory (data not published). 1369-703X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.bej.2011.04.005