Response of Lactiplantibacillus plantarum NMGL2 to Combinational Cold and Acid Stresses during Storage of Fermented Milk as Analyzed by Data-Independent Acquisition Proteomics.

Min Zhang,Tiantian Lai,Hua Zhao,Yihui Wang,Mengke Yao,Zhennai Yang

doi:10.3390/foods10071514

Min Zhang, Tiantian Lai + Show 4 more

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https://doi.org/10.3390/foods10071514

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Abstract

To understand the mechanism of tolerance of lactic acid bacteria (LAB) during cold storage of fermented milk, 31 LAB strains were isolated from traditional fermented products, and Lactiplantibacillus plantarum NMGL2 was identified with good tolerance to both cold and acid stresses. Data-independent acquisition proteomics method was employed to analyze the response of Lpb. plantarum NMGL2 to the combinational cold and acid stresses during storage of the fermented milk made with the strain at 4 °C for 21 days. Among the differentially expressed proteins identified, 20 low temperature-resistant proteins and 10 acid-resistant proteins were found. Protein interaction analysis showed that the low temperature-resistant proteins associated with acid-resistant proteins were Hsp1, Hsp2, Hsp3, CspC, MurA1, MurC, MurD, MurE1, and MurI, while the acid-resistant proteins associated with low temperature-resistant proteins were DnaA, DnaK, GrpE, GroEL, and RbfA. The overall metabolic pathways of Lpb. plantarum NMGL2 in response to the stresses were determined including increased cell wall component biosynthesis, extracellular production of abundant glycolipids and glycoproteins, increased expression of F1Fo-ATPase, activation of glutamate deacidification system, enhanced expression of proteins and chaperones associated with cell repairing caused by the acidic and cold environment into the correct proteins. The present study for the first time provides further understanding of the proteomic pattern and metabolic changes of Lpb. plantarum in response to combinational cold and acid stresses in fermented milk, which facilitates potential application of Lpb. plantarum in fermented foods with enhanced survivability.

Highlights

Functional lactic acid bacteria (LAB) have been widely applied in fermented milk that may be attributed with various functions such as promoting immunity [1], improving intestinal digestion [2], regulating intestinal flora [3], alleviating rheumatoid arthritis [4], relieving major depression [5], and inhibiting gastrointestinal inflammation [6]
Gene sequencing showed that there were 11 strains of Lpb. plantarum, seven strains of Levilactobacillus brevis, two strains of Lacticaseibacillus casei and one strain of Lactiplantibacillus pentosus. These 21 strains with good growth characteristics at 37 ◦ C were selected for further evaluation of their growth under low temperature condition
The LAB strains showed better tolerance with much better growth at 10 ◦ C than at 4 ◦ C for 72 h, except Lpb. plantarum p2 that was inhibited with little growth at the low temperatures

Summary

Introduction

Functional lactic acid bacteria (LAB) have been widely applied in fermented milk that may be attributed with various functions such as promoting immunity [1], improving intestinal digestion [2], regulating intestinal flora [3], alleviating rheumatoid arthritis [4], relieving major depression [5], and inhibiting gastrointestinal inflammation [6]. During the cold storage of fermented milk, LAB strains are exposed to long-time low temperature and acid stresses, leading to sublethal or even lethal effects on the strains, the reduced functionality of the products specially at the later stage of the storage [7,8]. The response and the relevant mechanism of the LAB strains against the combined stresses of cold and acid in fermented milk have not been studied. E.g., Bacillus subtilis, a temperature downshift causes a transient cell growth arrest, during which general protein synthesis is severely inhibited. Under these conditions, the synthesis of cold shock proteins (Csps) is triggered. Csps have been shown to regulate the expression of cold-induced genes such as anti-terminators [10]

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