Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Nov 8:8:2158.
doi: 10.3389/fmicb.2017.02158. eCollection 2017.

Characterization of Pseudomonas spp. and Associated Proteolytic Properties in Raw Milk Stored at Low Temperatures

Lu Meng  1   2 , Yangdong Zhang  1   2 , Huimin Liu  1   2 , Shengguo Zhao  1   2 , Jiaqi Wang  1   2 , Nan Zheng  1   2
Affiliations

Characterization of Pseudomonas spp. and Associated Proteolytic Properties in Raw Milk Stored at Low Temperatures

Lu Meng et al. Front Microbiol. .

Abstract

Milk spoilage is caused by the presence of proteolytic enzymes produced by Pseudomonas spp. during storage at low temperatures. The aim of this study was to identify Pseudomonas spp. in raw milk and investigate their associated proteolytic properties at low temperatures. Raw milk samples (n = 87) were collected from 87 bulk tanks in Shaanxi Province in China. Pseudomonas spp. were identified using Pseudomonas specific 16S, universal 16S rRNA sequencing, and rpoB gene sequencing. The proteolytic properties of Pseudomonas spp. were examined using milk agar, quantitative trinitrobenzenesulfonic acid assay, and by the presence of alkaline metallopeptidase gene (aprX). A total 143 isolates from all 87 samples were confirmed as Pseudomonas, and were identified as belonging to 14 Pseudomonas species. Of these, 40 (28.0%) isolates revealed proteolysis on milk agar at 2°C, 74 (51.8%) at 4°C, 104 (72.7%) at 7°C, and 102 (71.3%) at 10°C. However, proteolytic activity of 45 (31.5%) isolates exceeded 2 μmol of glycine equivalents per mL at 7°C, followed by 43 (30.1%) at 10°C, 18 (12.6%) at 4°C, and 7 (4.9%) at 2°C. The results reveal proteolytic activity of Pseudomonas spp. present in milk and their spoilage potential at different temperatures.

Keywords: Pseudomonas spp.; aprX gene; milk; proteolytic activities; spoilage.

PubMed Disclaimer

Figures

FIGURE 1
FIGURE 1
Proteolytic activity quantification of Pseudomonas isolates obtained from raw cow milk samples stored for 5 days at 2°C (A), 4°C (B), 7°C (C), and 10°C (D). The X-axis represents the storage day when the isolates displayed extracellular peptidase activity on milk agar, and the Y-axis represents proteolytic activity (μmol of glycine equivalents per mL). Species names and isolate numbers are not indicated.
See this image and copyright information in PMC

References

    1. Anzai Y., Kim H., Park J. Y., Wakabayashi H., Oyaizu H. (2000). Phylogenetic affiliation of the pseudomonads based on 16S rRNA sequence. Int. J. Syst. Evol. Microbiol. 50 1563–1589. 10.1099/00207713-50-4-1563 - DOI - PubMed
    1. Baur C., Krewinkel M., Kranz B., von Neubeck M., Wenning M., Scherer S., et al. (2015). Quantification of the proteolytic and lipolytic activity of microorganisms isolated from raw milk. Int. Dairy J. 49 23–29. 10.1016/j.idairyj.2015.04.005 - DOI
    1. Caldera L., Franzetti L., Van Coillie E., De Vos P., Stragier P., De Block J., et al. (2016). Identification, enzymatic spoilage characterization and proteolytic activity quantification of Pseudomonas spp. isolated from different foods. Food Microbiol. 54 142–153. 10.1016/j.fm.2015.10.004 - DOI
    1. Chabeaud P., de Groot A., Bitter W., Tommassen J., Heulin T., Achouak W. (2001). Phase-variable expression of an operon encoding extracellular alkaline protease, a serine protease homolog, and lipase in Pseudomonas brassicacearum. J. Bacteriol. 183 2117–2120. 10.1128/JB.183.6.2117-2120.2001 - DOI - PMC - PubMed
    1. Chakravarty S., Gregory G. (2015). “The genus Pseudomonas,” in Practical Handbook of Microbiology eds Goldman E., Green L. H. (New York, NY: CRC Press; ) 321–344.

LinkOut - more resources