Short Communication The use of Lactobacillus brevis PS1 to in vitro inhibit the outgrowth of Fusarium culmorum and other common Fusarium species found on barley A. Mauch a,b , F. Dal Bello a,b , A. Coffey c , E.K. Arendt a, ⁎ a Department of Food Science, Food Technology and Nutrition, National University of Ireland, Cork, Ireland b National Food Biotechnology Centre, National University of Ireland, Cork, Ireland c Department of Biological Sciences, Cork Institute of Technology, Bishopstown, Cork, Ireland abstract article info Article history: Received 15 December 2009 Received in revised form 15 April 2010 Accepted 1 May 2010 Keywords: Antifungal Lactobacillus Fusarium spp. Mycelia growth Macroconidia Inhibition A total of 129 lactic acid bacteria (LAB) were screened for antifungal activity against common Fusarium spp. isolated from brewing barley. Four out of the five most inhibiting isolates were identified as Lactobacillus brevis, whereas one belonged to Weissella cibaria. L. brevis PS1, the isolate showing the largest inhibition spectrum, was selected and the influence of its freeze-dried cell-free supernatant (cfsP) on germination of macroconidia as well as mycelia growth was investigated using Fusarium culmorum as target organism. Addition of cfsP into the growth medium at concentrations ≥2% altered the growth morphology of F. culmorum, whereas at concentrations N 5% the outgrowth of germ tubes from macroconidia was delayed and distorted. The presence of 10% cfsP completely inhibited the outgrowth of F. culmorum macroconidia. The activity of the compounds produced by L. brevis PS1 was higher at low pH values, i.e. pH b 5. Heating and/or proteolytic treatment reduced the inhibitory activity of cfsP, indicating that L. brevis produces organic acids and proteinaceous compounds which are active against Fusarium spp. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The mycotoxigenic fungi associated with the human food chain belong mainly to the three genera Aspergillus, Fusarium and Penicillium (Pitt et al., 2000). Aspergillus and Penicillium species are reported as spoilage organisms from a wide range of food and feeds, whereas Fusarium species are often found on cereal grains (Filtenborg et al., 1996; Samson et al., 2000). In grain processing, mycotoxin secretion by storage fungi like Aspergillus or Penicillium species can be prevented by the selection of appropriate storage conditions of the grains. This approach does not apply for field fungi. Therefore field fungi represent an important threat to the safety of cereal products (Noots et al., 1999). Although processing, notably heat treatment, can reduce mycotoxin concentrations significantly, it does not eliminate them completely (Bullerman and Bianchini, 2007; Ryu et al., 2002). Safety of raw materials and food products can be assured by the use of chemical preservatives. However, during the last decades the application of these compounds has been questioned. In particular, the enhanced interest in natural and free-from foods, preferentially with health- promoting characteristics has forced the food makers to find alter- native solutions. The applications of lactic acid bacteria (LAB) as starter cultures as well as their metabolites are a matter of particular interest to perform this task. LAB have a long history of application in fermented foods because of their beneficial influence on nutritional, organoleptic, and shelf-life characteristics, and are naturally occurring in many food systems (De Vuyst and Leroy, 2007; Tamminen et al., 2004; Vaughan et al., 2001). There is an extensive knowledge about antibacterial compounds, especially bacteriocins, produced by LAB (Aso et al., 2008; De Vuyst and Leroy, 2007; Elegado et al., 2007; Ghrairi et al., 2007; Millette et al., 2008; Oguntoyinbo, 2007) whereas the number of published studies on the identification of antifungal compounds produced by LAB is rather limited. Several low molecular weight compounds, mostly organic acids, have been isolated with the ability to retard or eliminate fungal growth or spores outgrowth, either on their own or synergis- tically (Batish et al., 1997; Dal Bello et al., 2007; Lavermicocca et al., 2003; Lind et al., 2007; Ryan et al., 2008; Schnurer and Magnusson, 2005). Regarding the great diversity of LAB within a single species, particularly due to environmental adaptions, there is a strong justification for further studies aimed at identifying novel antifungal LAB and characterising the compounds responsible for their inhibitory activity. The ambition of this study was to find LAB isolated from different sources like cheese as well as human, mouse, pig and bovine intestinal sources exhibiting antifungal activity against a variety of important Fusarium species commonly found on barley. International Journal of Food Microbiology 141 (2010) 116–121 ⁎ Corresponding author. Tel.: + 353 21 4902064; fax: + 353 21 4270213. E-mail address: e.arendt@ucc.ie (E.K. Arendt). 0168-1605/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.ijfoodmicro.2010.05.002 Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro