Evaluation of whisky distillery by‐products. VI. The reduction in digestibility of malt distiller's grains by fatty acids and the interaction with calcium and other reversal agents

Abstract

In vitro methods have been used to study the inhibitory effects of fat and fatty acids which reduce the digestibility of malt distiller's grains (MDG). Glycerol and individual fatty acids below Cs in the homologous series do not produce any measurable decrease in digestibility. Capric acid lowers digestibility appreciably and the depression is even greater with lauric acid. Myristic, palmitic and stearic acids are less active than lauric and the greatest depressions were recorded with the unsaturated acids which showed greater activity with increasing unsaturation. Calcium salts produced partial reversal of digestibility in the presence of saturated acids above C,, and substantially greater reversal with the CI8 unsaturated acids. The reduction in digestibility of MDG and in steam volatile acid production in the digesta by the presence of native fat may be attributed to the high content of oleic and linoleic acids which can also account Sor the marked reversal of effects by calcium. Alkaline earth metals and iron were examined for reversibility but only calcium produced consistent effects. Addition of ergocalciferol produced reversal effects similar to calcium. The reversal by calcium was evident when the calcium was added to the digesta up to 8 h after the commencement of incubation which indicates that the fatty acids have a bacteriostatic effect. In in vivo digestibility trials sheep consumed increasing amounts of dried MDG when the level of calcium supplementation was increased. Rations containingfat levels similar to that of MDG should be supplemented with calcium at levels higher than normal requirements of the element.

Fermentative degradation of nonionic surfactants and polyethylene glycol by enrichment cultures and by pure cultures of homoacetogenic and propionate-forming bacteria

“…Probably, the alcohol cannot cross the cytoplasmic membrane in its free form. Fatty acids with chain lengths of 8 to 16 C atoms can be toxic to anaerobic microbial communities to a varying extent (10,14,16,17). The gram-positive strain KoB58 appeared to withstand more fatty acids than the gram-negative strain KoB35.…”

Effect of Long Chain Fatty Acids on Bacterial Respiration and Amino Acid Uptake

“…It has been shown that anaerobic transport systems are sensitive to inhibition and that Gram negative bacteria are inhibited to a limited extent. The marked, but not complete reduction in cellulose digestibility (El Hag & Miller, 1972) may have been due to the fatty acid-induced reductions in the uptake of essential metabolites by the bacteria responsible and hence reduced growth. The inhibition of ruminant methane production by fatty acids (Blaxter & Czerkawski, 1966;Demeyer & Henderickx, 1967) may occur similarly since uncouplers of oxidative phosphorylation have been shown to inhibit the energy metabolism of a species of methane-producing bacteria (Robertson & Wolf, 1971).…”

Inhibition of Methanogenesis from Acetate in Granular Sludge by Long-Chain Fatty Acids

“…Basal medium. The basal medium used in all experiments contained (in milligrams per liter) NH4Cl (174), Na2HPO4 2H20 (37), and Na2SO4 (7). The medium was made up in Wageningen tap water, which contains approximately 35 mg of calcium ions per liter.…”