Peptide Identification and Expression Analysis of Genes Involved in Inulin Metabolism in Lactobacillus casei AP

Abstract

Background and objective: Lactobacillus casei AP are probiotic bacteria found in the gastrointestinal tracts of Indonesian breast-fed infants. Lactobacillus casei AP can degrade inulin through metabolic pathways that involve certain proteins. However, detailed information on how inulin is metabolized by this strain is limited. The aim of this study was to identify intracellular proteins that play roles in metabolism of inulin. Material and methods: Bacteria were cultured on media containing commercial inulin or inulin extracted from dahlia tubers as the sole carbon source and protein identification was carried out using intracellular extraction. The bacterial intracellular proteins were isolated and separated using sodium dodecyl sulphate-polyacrylamide gel electrophoresis and then peptides were identified using electrospray ionization-liquid chromatography-mass spectrometry. Based on the identified proteins, corresponding genes involved in inulin metabolism were identified and their expression levels were quantified using quantitative real time-polymerase chain reactions. Results and conclusion: Comparisons of intracellular proteins from Lactobacillus casei AP cultured in inulin and MRS control media showed a different protein band at 70 kDa in bacterial cells cultured in inulin or inulin extract. This protein was identified as a glycoside hydrolase (α-2,1 glycosidic) with a gene expression value of 1.55 or a fructan hydrolase (β-2,1 fructo-furanosidic) with a gene expression value of 2.68, compared to controls. Conflict of interest: The authors declare no conflict of interest.

Keywords

• ▪ Dahlia tuber ▪ Fructan hydrolase ▪ Glycoside hydrolase ▪ Inulin ▪ Peptide identification