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| Optimization of the quenching method for metabolomics analysis of Lactobacillus bulgaricus |
| Ming-ming Chen, Ai-li Li, Mao-cheng Sun, Zhen Feng, Xiang-chen Meng, Ying Wang |
| MOE Key Laboratory of Dairy Science, College of Food Science, Northeast Agricultural University, Harbin 150030, China; School of Public Health, Jilin Medical College, Jilin 132013, China |
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Abstract This study proposed a quenching protocol for metabolite analysis of Lactobacillus delbrueckii subsp. bulgaricus. Microbial cells were quenched with 60% methanol/water, 80% methanol/glycerol, or 80% methanol/water. The effect of the quenching process was assessed by the optical density (OD)-based method, flow cytometry, and gas chromatography-mass spectrometry (GC-MS). The principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were employed for metabolite identification. The results indicated that quenching with 80% methanol/water solution led to less damage to the L. bulgaricus cells, characterized by the lower relative fraction of prodium iodide (PI)-labeled cells and the higher OD recovery ratio. Through GC-MS analysis, higher levels of intracellular metabolites (including focal glutamic acid, aspartic acid, alanine, and AMP) and a lower leakage rate were detected in the sample quenched with 80% methanol/water compared with the others. In conclusion, we suggested a higher concentration of cold methanol quenching for L. bulgaricus metabolomics due to its decreasing metabolite leakage.
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Received: 24 May 2013
Published: 06 April 2014
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