Molecular characterization of Lactobacillus plantarum DMDL 9010, a strain with efficient nitrite degradation capacity.

Yong-Tao Fei,Hui Wu,Li Li,Tong-Hui Luo,Yi-Gang Yu,Dong-Mei Liu,Gu Chen,Wenjun Li

doi:10.1371/journal.pone.0113792

Abstract

Nitrites commonly found in food, especially in fermented vegetables, are potential carcinogens. Therefore, limiting nitrites in food is critically important for food safety. A Lactobacillus strain (Lactobacillus sp. DMDL 9010) was previously isolated from fermented vegetables by our group, and is not yet fully characterized. A number of phenotypical and genotypical approaches were employed to characterize Lactobacillus sp. DMDL 9010. Its nitrite degradation capacity was compared with four other Lactobacillus strains, including Lactobacillus casei subsp. rhamnosus 719, Lactobacillus delbrueckii subsp. bulgaricu 1.83, Streptococcus thermophilus 1.204, and lactobacillus plantarum 8140, on MRS medium. Compared to these four Lactobacillus strains, Lactobacillus sp. DMDL 9010 had a significantly higher nitrite degradation capacity (P<0.001). Based on 16S rDNA sequencing and sequence comparison, Lactobacillus sp. DMDL 9010 was identified as either Lactobacillus plantarum or Lactobacillus pentosus. To further identify this strain, the flanking regions (922 bp and 806 bp upstream and downstream, respectively) of the L-lactate dehydrogenase 1 (L-ldh1) gene were amplified and sequenced. Lactobacillus sp. DMDL 9010 had 98.92 and 76.98% sequence identity in the upstream region with L. plantarum WCFS1 and L. pentosus IG1, respectively, suggesting that Lactobacillu sp. DMDL 9010 is an L. plantarum strain. It was therefore named L. plantarum DMDL 9010. Our study provides a platform for genetic engineering of L. plantarum DMDL 9010, in order to further improve its nitrite degradation capacity.

Highlights

Amongst all processed vegetables, fermented vegetables have the highest productivity and are important Asian cuisine
Lactobacillus delbrueckii subsp. bulgaricus 1.83 and Streptococcus thermophiles 1.204 were purchased from Guangdong Institute of Microbial Culture Collection (GIMCC) and Lactobacillus plantarum 8140 was purchased from China General Microbiological Culture Collection (CGMCC)
We characterized a Lactobacillus strain that was previously isolated from fermented vegetables and exhibited significant nitrite degradation capability, using a number of phenotypical and genotypical approaches, including physiological and biochemical characterization, 16S rDNA sequencing, and DNA sequencing of flanking regions of the L-lactate dehydrogenase 1 (L-ldh1) gene

Summary

Introduction

Amongst all processed vegetables, fermented vegetables have the highest productivity and are important Asian cuisine. Understanding the degradation of salt and nitrites during the process of vegetable fermentation is critically important to food safety. Certain salt-tolerant Lactobacillus species are widely used in vegetable fermentation [4]. Preliminary results suggested that the DMDL 9010 strain can inhibit the nitrite accumulation in vegetable fermentation and that the fermentation can be completed within 24 hours without the addition of salt. Detailed characterization of this strain is important to understand the underlying mechanism of the nitrite degradation, and may facilitate its utilization in vegetable fermentation with genetic engineering. We aimed to characterize DMDL 9010, using a number of phenotypical and genotypical approaches

Objectives

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Conclusion