Partial characterisation of bacteriocins produced by lactic acid bacteria isolated from Thai fermented meat and fish products Onanong Pringsulaka * , Narumon Thongngam, Nuttika Suwannasai, Wisrutta Atthakor, Kajeenart Pothivejkul, Achariya Rangsiruji Department of Biology, Faculty of Science, Srinakharinwirot University, Wattana, Bangkok 10110, Thailand article info Article history: Received 25 March 2011 Received in revised form 6 August 2011 Accepted 13 August 2011 Keywords: Weissella cibaria Bacteriocins Lactic acid bacteria Thai fermented meat and fish products abstract Lactic acid bacteria (LAB) from Thai fermented meat and fish products were isolated. From a total of 93 samples, 152 isolates of lactic acid bacteria were obtained. Antimicrobial activity screening was per- formed using the agar spot test and the agar well diffusion method. Of the six isolates which produced antimicrobial activities against Weissella confusa N31, only isolate N23 was identified as Weissella cibaria (GenBank accession number AB494716.1) with 99% similarity by 16S rDNA sequence analyses. Complete inactivation of antimicrobial activity produced by W. cibaria N23 was observed after treatment of the bacteriocins with trypsin, actinase, protease XIII, ficin, trypsin from porcine pancreas, a-chymotrypsin and pepsin. In addition, the inhibitory activities were not affected by the addition of catalase. Taken together, these results confirmed that the inhibitory compounds produced by this strain were protein- aceous in nature and possessed typical characteristics of bacteriocins. The highest yield of bacteriocin produced by W. cibaria N23 was recorded at 20 h. The bacteriocin N23 remained stable after 2 h of incubation at pH values between 2.0 and 8.0, and also for 15 min at 121  C. The bacteriocin produced by W. cibaria N23 was found to have a narrow antibacterial spectrum, being able to inhibit only W. confusa N31. In addition, bacteriocin N23 did not adhere to the surface of the producer cells. The results produced from this study will contribute to the existing body of knowledge and enhance the databases of bacteriocin-producing Weissella. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction At present, the trend towards greater food safety is attracting a significant amount of interest. The use of chemical preservatives to prevent food spoilage and inhibit food-borne pathogens is being questioned due to lack of consumer acceptance and potential health risks. Since consumers are becoming increasingly health aware, the application of bacteriocins as a natural preservative in food has recently received considerable attention (Papagianni & Anastasiadou, 2009). Thai fermented meats are produced naturally, using raw mate- rials available locally in each area of Thailand. Common to all Thai fermented products, salt and other ingredients such as rice bran, pepper, minced garlic and chilies are usually added to the meat. The mixture is then left in a jar or wrapped tightly in banana leaves or a plastic bag and allowed to ferment for several days or months depending on the kind of products. Throughout Thailand’s history, fermented meats, including Nham (Thai fermented pork), Sai Krok Preaw (fermented pork sausage) and Plaa-ra (Thai fermented fish), have been, and remain, widely consumed by the Thai people. Generally, such fermented meats are carried out naturally by lactic acid bacteria (LAB). Through natural fermentation, the products become acidic (pH approximately 4.5) and develop a sour flavour. Like most other meat fermentations, Nham fermentation relies on indigenous lactic acid bacteria; however, the development of pilot- and large-scale fermented food manufacture requires a lactic starter culture for high productivity. Lactic acid bacteria (LAB) are a diverse group of microorganisms that produce lactic acid as the primary end-product of the fermentation of carbohydrates (Carr, Chill, & Maida, 2002). LAB are Gram positive, non-spore forming, catalase-negative, and acid- tolerant. They have a low GC content, and are either facultatively anaerobic or microaerophilic. LAB produce a variety of bacteriocins, most of which can be grouped into the classes described by Klaenhammer (1993). Since bacteriocins produced by LAB are considered to be Generally Recognized as Safe microorganisms * Corresponding author. Tel.: þ66 (2)649 5000x8517; fax þ66 (2)260 0127. E-mail addresses: opringsulaka@gmail.com, onanong@swu.ac.th (O. Pringsulaka). Contents lists available at SciVerse ScienceDirect Food Control journal homepage: www.elsevier.com/locate/foodcont 0956-7135/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodcont.2011.08.029 Food Control 23 (2012) 547e551