Metabolic Properties of Lacticaseibacillus paracasei Zhang ΔpglX during Continuous Passage Culture

The aim of this study was to investigate the metabolite changes in Lacticaseibacillus paracasei Zhang ΔpglX, a DNA methyltransferase mutant, after successive passages and to explore the possible mechanism of metabolic regulation during the passage process. We monitored the morphological characteristics and changes in the carbohydrate-metabolizing capacity of this strain. The metabolites at different passages were characterized using ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS) combined with principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). The identification of significantly differential metabolites and the key metabolic pathways involving them was performed through Kyoto Encyclopedia of Genes and Genomes (KEGG) database annotation. The phenotype of L. paracasei Zhang ΔpglX exhibited stable inheritance during successive passages, but the metabolic profile changed with increasing passage. The differential metabolites were mainly enriched in organic heterocyclic compounds, nucleosides, nucleotides and their analogs, lipids and lipid-like molecules, and the nucleotide metabolic pathway was the most dominant enriched pathway, which agreed with the results of differential metabolite enrichment analysis. These results suggested that L. paracasei Zhang ΔpglX could adapt to environmental changes by adjusting metabolic pathways, providing new insights into metabolic pathway changes in Lactobacillus during adaptive evolution.