Journal of Pure and Applied MicrobiologyVol. 7 No. 4

Isolation and Characterization of an Antimicrobial Compound Produced by Lactobacillus casei C7-2

Tie-Dan Zhang1#, Yun-Zhi Shi3#, Zhi-Wei Ye1,2, Li-Qiong Guo1,2 and Jun-Fang Lin1,2*

1Department of Bioengineering, College of Food Science, South China Agricultural University, 483 Wushan Road, Tianhe District, Guangzhou - 510 640, China. 2Institute of Biomass Research, South China Agricultural University, Guangzhou - 510 640, China. 3Beijing tiantan Biological Products Corporation Limited, Beijing - 100 024, China.

Received on 23 September 2013 and accepted on 06 November 2013

 

ABSTRACT

In this study, a Lactobacillus casei strain (C7-2) that produced broad spectrum antifungal compounds was isolated from fermented pickle samples. This strain was identified by the analyses of morphologic characteristics, physiological-biochemical tests, and molecular-biological test. The highest yield of the antimicrobial substances produced by this strain was recorded at 36 h. The antimicrobial compound remained stable at pH values between 2.0 to 6.0, and also for 30 min at 121 ?C. The antimicrobial compound produced by the strain C7-2 was found to have a wide antimicrobial spectrum, which effectively inhibit Escherichia coli, Bacillus subtilis, Staphylococcus aureus, Salmonella, Saccharomyces cerevisiae, and Botryodiplodia theobromae Pat. This antimicrobial compound was purified using silica gel column chromatography, VLC, and HPLC. The structure of this compound was elucidated using NMR (1HNMR, 13CNMR). The active compound was identified as 2,5-diketopiperazines (DKPS) [cyclo (l-Pro-d-Leu)]. The diketopiperazine derivative identified in the study may be a promising alternative to chemical preservatives as a potential bio-preservative which prevent fungal growth and mycotoxin formation in food and feed. This is the first report on the isolation of this DKPS from L. casei.

Keywords : Lactobacillus casei; Fermented pickle; Antimicrobial compound; Chromatography; Diketopiperazines.