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Lactobacillus Casei: A Conjugated Linoleic Acid Producing Bacterium

Probiotics are living microorganisms that benefit human health when ingested in adequate doses. Probiotics produce several metabolic compounds with bioactive properties, including conjugated linoleic acid (CLA)1.

Fermentation using specific lactic acid bacteria (LAB) starter cultures in milk and meat can increase the content of conjugated linoleic acid. In a previous study the CLA-producing LAB were identified as Lactobacillus plantarum strain was found to produce the highest conjugated linoleic acid levels1.

Previously researchers had isolated Lactobacillus casei strain AG from the human gastrointestinal tract, for its potential use as a probiotic. Based on an in silico analysis, the L. casei strain AG has one or more homologous of the L. plantarum AKU 1009a genes that were responsible for conjugated linoleic acid synthesis2.

Therefore, in the aaobce mentioned context a new study was conducted to investigate the ability of the L. casei strain AG to synthesize conjugated linoleic acid during milk fermentation and to measure the transcription level of CLA-synthesis genes upon the addition of Linoleic Acid3.

CLA in milk fermented by the L. casei strain AG and corresponding non-fermented milk standard was detected in the form of fatty acid methyl esters (FAME). FAME forms of CLA and LA can be distinguished by gas spectrometry, due to their different retention times and same molecular weights. Fresh milk (non-fermented milk standard) used in the study contained linoleic acid but does not include conjugated linoleic acid. GC-MS results showed that milk fermented by the L. casei strain AG contained conjugated linoleic acid.

The identified genes were cla-hy, cla-dh and cla-dc genes. The nucleotide sequences of these genes from L. plantarum AKU 1009a were aligned with the genome of L. casei strain. The size of the amplification products obtained from L. casei strain AG, using the three selected primer pairs, correlated with the predicted target lengths.

The study discovered the synthesis of conjugated linoleic acid (CLA) in milk fermented with L. casei strain AG. The ability of L. casei AG to synthesize CLA in fermented milk can be beneficial for human health. The study will support the utilization of L. casei AG as starter culture for dairy fermentation and thus develop probiotic-based food industries.


Lactobacillus casei strain AG, milk fermentation, CLA (Conjugated Linoleic Acid), homologue genes, transcription, synthesize, starter culture, probiotic-based food industries, genome alignment, non-fermented milk standard, fatty acid methyl esters.


  1. Kishino, S., J. Ogawa, A. Ando, T. Iwashita, T. Fujita, H. Kawashima and S. Shimizu, 2003. Structural analysis of conjugated linoleic acid produced by Lactobacillus plantarum and factors affecting isomer production. Biosci. Biotechnol. Biochem., 67: 179-182.
  2. Widodo, T.T. Taufiq, E. Aryati, A. Kurniawati and W. Asmara, 2012. Human origin Lactobacillus casei isolated from Indonesian infants demonstrating potential characteristics as probiotics in vitro. Indonesian J. Biotechnol., 17: 79-89.
  3. Widodo, Sukarno A.R., Estancia, K., Widianto D. and Indratiningsih , 2018. Conjugated Linoleic Acid Synthesis in Milk Fermented with Lactobacillus casei Strain AG. Pak. J. Nutr., 17: 524-529.

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