|Kim, Y - CORNELL UNIVERSITY|
|Rychlik, J - CORNELL UNIVERSITY|
|Liu, R - CORNELL UNIVERSITY|
Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 2001
Publication Date: N/A
Technical Abstract: Conjugated linoleic acid (CLA) causes milkfat depression in dairy cattle and a change in body fat composition in other species. Diets containing linoleic acid (LA) and grain diet stimulates trans-10,cis-12 CLA production and milk fat depression, but predominant ruminal bacteria capable of producing trans-10,cis-12 CLA production had not been isolated. Mixed ruminal bacteria from cattle fed grain or hay were incubated with LA and trans-10,cis-12 CLA production was monitored by gas chromatography. Mixed ruminal bacteria from a cow fed grain were enriched with lactate and Trypticase and a trans-10,cis-12 CLA producing bacterium was isolated. Particle attached bacteria(PAB) were more active in biohydrogenation than free-floating bacteria(FFB), but FFB produced more CLA. FFB from grain-fed cows produced more trans-10,cis-12 CLA than FFB from hay-fed cows. When FFB from grain-fed cows were provided with lactate and Trypticase, the optical density and trans-10,cis-12 CLA increased. Trans-10,cis-12 CLA producing bacteria were isolated from culture enriched with lactate and Trypticase YJ-4 produced the most trans-10,cis-12 CLA among the isolated strains. 16S-rDNA sequencing indicated that YJ-4 was closely related to Megasphaera elsdenii. YJ-4 cultures that had been grown with lactate produced moretrans-10,cis-12 CLA than cultures grown on glucose. The trans-10,cis-12 CLA production was first order with respect to the cell mass, but not LA concentration. Cattle fed grain had ruminal bacteria that produced large amounts of trans-10,cis-12 CLA, and we isolated a trans-10,cis-12 CLA producing bacterium that could be classified as M. elsdenii. M. elsdenii is a lactate utilizing bacterium that is common in cattle fed grain, but this is the first report that it can produce trans-10,cis-12 CLA.