Increase in the CLA Conversion Rate and Transcription Level of CLA-Related Enzymes in Lactobacillus plantarum p-8 Following Ethanol Stress
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Abstract:
The effects of the presence of linoleic acid (LA) and ethanol on the conjugated linoleic acid (CLA) conversion rates and the transcription level of CLA synthesis-related enzymes of Lactobacillus plantarum p-8 (L. plantarum p-8) were studied. For this, 0.05 mg/mL LA and ethanol at different concentrations were added to MRS media. The results showed that the conversion rates of the three CLA isomers were the highest when 0.50% ethanol was added to the fermentation broth. More specifically, the conversion rate of the cis9, trans11-CLA (c9,t11-CLA) isomer was the highest, reaching up to 2.49%, which was 2.37 times higher than that observed without ethanol. The conversion rate of the trans10, cis12-CLA (t10,c12-CLA) isomer in the fermentation broth was the lowest, regardless of the concentration of ethanol added. The CLA conversion rates were much higher in the fermentation broths compared to those observed in the bacteria, and the CLA conversion rates in the bacteria were very low, but the variations in the CLA conversion rates following ethanol addition were consistent between the fermentation broths and the bacteria. The conversion rate of the c9,t11-CLA isomer was the highest (0.05%) in the bacteria following 0.50% ethanol treatment. This rate is five times higher than that obtained without ethanol treatment. When the ethanol concentration was higher than 0.50%, the conversion rates of all CLA isomers were reduced. The results indicate that CLA is produced in the cytosol and then transferred to the extracellular environment. Meanwhile, the transcription levels of the genes encoding CLA synthesis-related enzymes increased following ethanol stress within a certain concentration range, and accordingly, the CLA conversion rates increased. It is confirmed that the variation in the transcription levels of the CLA synthesis-related enzyme genes is the main reason for the differences in the CLA conversion rates. The results provide a foundation for elucidating the molecular mechanism of CLA production by Lactobacillus plantarum p-8 and for exploring effective regulation methods to improve CLA production.
