Hydrogenation in vitro of -Linolenic Acid to Stearic Acid by Mixed Cultures of Pure Strains of Rumen Bacteria

Abstract

The hydrogenation of α-linolenic acid to stearic acid which occurs with the mixed bacteria of the sheep rumen can be demonstrated in vitro by mixing exponential phase cultures of only two species of rumen bacteria and incubating for a further period with α-linolenic acid. One bacterium must be able to hydrogenate α-linolenic acid to predominantly trans-octadec-11-enoic acid which is then used 11 substrate by a second bacterium. Cultures grown from small mixed inocula failed, with the exception of one pair of bacteria, to hydrogenate α-linolenic acid to stearic acid. The products from these cultures showed that one of the pair of bacteria had outgrown the other. For stearate production it was necessary to use inocula with a minimum number of cells rather than cells in a particular phase of growth. Two of the bacteria used, P2/2 and T344, after several years in pure culture show an increased isomerization of the octadecenoic acid products.