ORIGINAL ARTICLE In vitro cholesterol-lowering properties of Lactobacillus plantarum AN6 isolated from aji-narezushi T. Kuda, T. Yazaki, M. Ono, H. Takahashi and B. Kimura Department of Food Science and Technology, Tokyo University of Marine Science and Technology, Tokyo, Japan Significance and Impact of the Study: Lactobacillus plantarum AN6 was isolated from aji-narezushi. Cho- lesterol-lowering activity of AN6 was higher than ones of the type strain. Cell surface of AN6 was rough. FT-IR analysis indicated that the content of cell wall polysaccharides of AN6 is higher than ones in the type strain. These results indicate that AN6 can be used as a new profitable starter and probiotic. Keywords cholesterol lowering, Fourier transform infrared, Lactobacillus plantarum, narezushi. Correspondence Takashi Kuda, Department of Food Science and Technology, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Minato-ku, Tokyo 108-8477, Japan. E-mail: kuda@kaiyodai.ac.jp 2013/0556: received 21 March 2013, revised 25 April 2013 and accepted 25 April 2013 doi:10.1111/lam.12094 Abstract Aji-narezushi is a traditional lactic acid-fermented fish. In this study, we screened for lactose-utilizing, acidophilic, bile-resistant and cholesterol- lowering lactic acid bacteria (LAB) from aji-narezushi for use as starter strains for fermented foods, as well as for use as probiotics. Of the 301 LAB isolates, 277 fermented lactose, and among these, 171 grew in de Man, Rogosa and Sharpe broth adjusted to pH 3Á5. Thirty-four of the isolates were grown in a broth containing 3% (w/v) bile. All of the isolates were lactobacilli. Seven isolates that demonstrated cholesterol-lowering activity in ethanolic solution were selected. All of the isolates were identified as Lactobacillus plantarum. Lactobacillus plantarum AN6 showed the highest cholesterol-lowering activity. AN6 was more resistant to acid, salt and bile than the type strain NBRC15891 T . One-half of the cholesterol-lowering effect remained after boiling AN6 for 10 min. The Fourier transform infrared (FT-IR) analysis indicated that the content of cell wall polysaccharides in AN6 is higher than ones in the type strain. These results indicate that Lact. plantarum AN6 can be used as a profitable starter organism and probiotic. Introduction Hypercholesterolaemia is a major human health problem, playing a role in cardiovascular disease (Aso et al. 2005) as well as various other diseases such as diabetes, osteo- porosis, Alzheimer’s disease, immune response disorders and cancers (Martens et al. 2008; Chen et al. 2011; Pelton et al. 2012). Therefore, many reports have dealt with the subject of cholesterol, particularly with respect to low-density lipoprotein (LDL) cholesterol, and the cholesterol-lowering effect of various chemicals and food materials (Nijjar et al. 2010). Among food materials, the cholesterol-lowering effect of dietary fibres, including soluble and indigestible polysaccharides such as pectin from fruits and alginate from brown algae, is well known (Kuda et al. 1997; Theuwissen and Mensink 2008). Certain lactic acid bacteria (LAB) and Bifidobacterium are regarded as probiotics, having health-promoting activ- ity associated with metabolism and immunity (Rijkers et al. 2010). The cholesterol-lowering effect of some probiotics has been reported. For example, Lactobacillus fermentum, Lact. delbrueckii ssp. bulgaricus, Lact. acidophilus, Lact. casei and Bifidobacterium animalis have shown cholesterol-lowering activity in vitro (Liong and Shah 2005; Alhaj et al. 2010; Tok and Aslim 2010). Further- more, the serum cholesterol-lowering effect of LABs in animals and/or humans was also reported (Sridevi et al. 2009; Lee et al. 2010). On the other hand, Yoon et al. (2011) reported that Lact. rhamnosus and Lact. plantarum promote cholesterol excretion in human enterocyte-like Caco-2 cells. In modern Japanese cuisine, sushi is made from vine- gar-flavoured rice combined with seafood. It is believed Letters in Applied Microbiology 57, 187--192 © 2013 The Society for Applied Microbiology 187 Letters in Applied Microbiology ISSN 0266-8254