Purification and Characterization of Plantaricin YKX and Assessment of Its Inhibitory Activity Against Alicyclobacillus spp.

Jinjin Pei,Wengang Jin,A M Abd El-Aty,Yonggui Zhang,Hongxia Zhang,Yigang Huang,Xinsheng Li,Amer Ramadan,Jinze Wang

doi:10.3389/fmicb.2021.783266

Abstract

Consumers prefer natural over synthetic chemical preservatives on a food label. Therefore, it is crucial to ensure the safety and efficacy of such natural preservatives. The emergence of heat-resistant spore-forming Alicyclobacillus spp. has been associated with spoilage problems in the fruit juice industry. Herein, a bacteriocin-producing stain YKX was isolated from the traditional pickles in Hanzhong City, China, and it was identified as Lactobacillus plantarum by morphological, biochemical, physiological, and genotypic features. A stable bacteriocin, plantaricin YKX, was isolated, purified, and tested for its efficacy against Alicyclobacillus acidoterrestris. Plantaricin YKX is a 14-amino acid peptide (Lys-Tyr-Gly-Asn-Gly-Leu-Ser-Arg-Ile-Phe-Ser-Ala-Leu-Lys). Its minimal inhibitory concentrations (MICs) against the tested bacterial and fungal strains were ranged from 16 to 64 μg/mL. It is thermostable and active at pH 3–8. The flow cytometry data and microscopic observations suggested that plantaricin YKX can augment cell membrane permeability, induce potassium ion leakage and pore formation, and disrupt cell membranes. It also affects spore germination and guaiacol production of A. acidoterrestris, probably due to upregulation of the luxS gene linked to quorum sensing.

Highlights

Bacteria, such as Alicyclobacillus species, spoil foods, juices, carbonated fruit beverages and shelfstable iced tea (Silva, 2016; Tremarin et al, 2017). Lee et al (2002) reported that 60% of respondents among 57 companies experienced spoilage incidents, of which 35% were due to Alicyclobacillus spp
Alicyclobacillus spp. (one strain DSMZ3922 purchased from Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ); 9 strains of A. acidoterrestris isolated from apple garden; and three strains of A. acidocaldarius isolated from apple juice processing lines by the previous study) (Yue et al, 2013) were cultured in Alicyclobacillus acidoterrestris medium (AAM) (Solarbio, Beijing, China) at 45◦C for 48 h (Pei et al, 2020)
The strain YKX was chosen for subsequent studies due to its significant inhibition against Alicyclobacillus spp. and several other spoilage and pathogenic microorganisms, including Grampositive and negative bacteria

Summary

Introduction

Bacteria, such as Alicyclobacillus species, spoil foods, juices, carbonated fruit beverages and shelfstable iced tea (Silva, 2016; Tremarin et al, 2017). Lee et al (2002) reported that 60% of respondents among 57 companies experienced spoilage incidents, of which 35% were due to Alicyclobacillus spp. Bacteria, such as Alicyclobacillus species, spoil foods, juices, carbonated fruit beverages and shelfstable iced tea (Silva, 2016; Tremarin et al, 2017). Lee et al (2002) reported that 60% of respondents among 57 companies experienced spoilage incidents, of which 35% were due to Alicyclobacillus spp. Various levels of contamination risk exist for diverse juice types, such as apple juice concentrates, 31–75%; orange juice concentrates, 82%; fresh juice, 32%; apple concentrates, 83% (Walker and Phillips, 2008); orange juice, 15%, and fruit concentrate, 8% (Osopale et al, 2017). The principal spoilage characteristic is an off-odor (Walker and Phillips, 2008; Tremarin et al, 2017), ascribed to the metabolites guaiacol and halophenol derivatives 2,6-dibromophenol and 2,6-dichlorophenol (Lee et al, 2002). Alicyclobacillus species present a grave threat to the juice industry and other industries

Methods

Results

Conclusion