Abstract
Megaspahera elsdenii YJ-4, which was previously isolated as a producer of trans-10, cis-12 CLA, was studied for its carbon source on the CLA production. M. elsdenii YJ-4, was incubated with glucose and lactose, and cultured in batch and continuous culture systems with linoleic acid at various pHs to investigate CLA production. Batch cultures of the ruminal bacterium, M. elsdenii YJ- 4, were resistant to stearic acid and linoleic acid, and little growth inhibition was observed even when the fatty acid concentration in the culture was as much as 4 mg ml -1 . Stationary phase batch cultures (0.25 mg bacterial protein ml -1 ) that had been grown on lactate and incubated with linoleic acid (0.20 mg ml -1 ) produced approximately 12 µg trans-10, cis-12 CLA mg protein -1 and little cis-9, trans-11 CLA was detected. Some linoleic acid was converted to hydrogenated products (chiefly stearic acid), but these fatty acids were less than 5 µg mg bacterial protein -1 . Stationary phase batch cultures that had been grown on glucose produced at least 3-fold less trans-10, cis-12 CLA than ones grown on lactate. Cells from lactate-limited continuous cultures produced less trans-10, cis-12 CLA than those from batch culture, but only if the pH was greater than 6.4. When the pH of the lactate-limited continuous cultures was lower than 6.4, trans- 10, cis-12 CLA and hydrogenated products declined. Cells from glucose-limited continuous cultures produced less trans-10, cis-12 CLA and hydrogenated products than the cells that had been limited by lactate, but pH had little impact on this production. These results support the idea that M. elsdenii YJ-4 could be one of the major producers of trans-10, cis-12 CLA which causes cows to produce milk with a low fat content. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 10 : 1425-1429)
Highlights
Conjugated linoleic acid (CLA) is a collective term for different positional and geometric isomers of octadecanoic acid with double bonds in a conjugate configuration
In the 1960's, Davis et al (1964) noted that dietary oil supplements accentuated the milk fat depression of cattle fed low fiber rations, but abomasal infusions of the same oil did not. These results suggested that milk fat depression was associated with changes in ruminal metabolism rather than a direct effect of the oils on the mammary gland per se
M. elsdenii YJ-4 batch cultures that were grown with either lactate or glucose as a carbon source were relatively resistant to linoleic acid, which serves as substrate for CLA production, and stearic acid, the final product of biohydrogenation
Summary
Conjugated linoleic acid (CLA) is a collective term for different positional and geometric isomers of octadecanoic acid with double bonds in a conjugate configuration. It was shown that B. fibrisolvens A38 accumulated cis9, trans-11 CLA when the substrate fat concentration was high enough to inhibit growth and CLA reduction to further saturated fatty acids (Kim et al, 2000).
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