Biohydrogenation of linoleic acid by rumen fungi compared with rumen bacteria.
OBJECTIVE
To investigate biohydrogenation of linoleic acid by rumen fungi compared with rumen bacteria, and to identify the fungus with the fastest biohydrogenation rate.


RESULTS
Biohydrogenation of linoleic acid by mixed rumen fungi and mixed rumen bacteria were compared in vitro. With mixed rumen bacteria, all biohydrogenation reactions were finished within 100 min of incubation and the end product of biohydrogenation was stearic acid. With mixed rumen fungi, biohydrogenation proceeded more slowly over a 24-h period. Conjugated linoleic acid (CLA; cis-9, trans-11 C18 : 2) was an intermediate product, and vaccenic acid (VA; trans-11 C18 : 1) was the end product of biohydrogenation. Fourteen pure fungal isolates were tested for biohydrogenation rate. DNA sequencing showed that the isolate with the fastest rate belonged to the Orpinomyces genus.


CONCLUSIONS
It is concluded that rumen fungi have the ability to biohydrogenate linoleic acid, but biohydrogenation is slower in rumen fungi than in rumen bacteria. The end product of fungal biohydrogenation is VA, as for group A rumen bacteria. Orpinomyces is the most active biohydrogenating fungus.


CONCLUSIONS
This is the first study to demonstrate that rumen fungi can biohydrogenate fatty acids. Fungi could influence CLA content of ruminant products.
Nam
I S
IS
Division of Agricultural and Environmental Sciences, University of Nottingham, School of Biosciences, Sutton Bonington Campus, Loughborough, UK.
Garnsworthy
P C
PC
D000818:Animals; D001419:Bacteria / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D005516:Food Microbiology; D005658:Fungi / Q000302:isolation & purification / Q000378:metabolism*; D006865:Hydrogenation; D019787:Linoleic Acid / Q000378:metabolism*; D044243:Linoleic Acids, Conjugated / Q000378:metabolism; D008297:Male; D020085:Neocallimastigales / Q000302:isolation & purification / Q000378:metabolism; D009829:Oleic Acids / Q000378:metabolism; D012417:Rumen / Q000382:microbiology*
D044243:Linoleic Acids, Conjugated; D009829:Oleic Acids; D019787:Linoleic Acid; C050413:11-octadecenoic acid