In vitro digestion of bloat-safe and bloat-causing legumes by rumen microorganisms: gas and foam production.

Leaves of three bloat-safe legumes -- birdsfoot trefoil (Lotus corniculatus L.), sainfoin (Onobrychis viciaefolia Scop.), and cicer milkvetch (Astralagus cicer L.) -- and of three bloat-causing legumes -- alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), and white clover (Trifolium repens L.) -- were incubated with strained rumen fluid or with mixed rumen fluid and solids. Gas released was measured during the early period (0 to 22 h) of this in vitro digestion. Gas volume was greater with a 1:1 (wt/vol) mixture of solid and fluid rumen contents than with rumen fluid alone. It was greater with whole and chewed leaves from the bloat-causing legumes than with whole leaves from the bloat-safe legumes. However, when leaves were homogenized, volumes of gas from bloat-causing and bloat-safe legumes were similar. More gas was released from homogenized leaves than from the same weight of whole leaves. The amount of foam produced on chewed herbage and homogenized leaves of bloat-causing legumes was greater than on those of bloat-safe legumes. These results are consistent with the rate of disintegration and digestion of legumes by rumen bacteria being an important determinant in pasture bloat. Measurement of gas produced early in in vitro digestion may provide a useful bioassay for evaluating the bloat-causing potential of legumes in breeding selections if variability of the method can be reduced.

Fermenting yeasts associated with softening and gas-pocket formation in olives.

Fermenting, pectolytic yeasts were isolated from a massive commercial outbreak of softening and gas-pocket formation in olives that had been stored in acidified, low-salt brines in an attempt to reduce the problem of brine disposal. The suspected yeasts represented three different species: Saccharomyces oleaginosus, S. kluyveri, and Hansenula anomala var. anomala. All pectolytic cultures produced pectin esterase and polygalacturonase but no pectic acid trans-eliminase when grown in nutrient glucose broth. Crude, cell-free dialyzed enzyme preparations measured viscosimetrically exhibited optimal activity on sodium polygalacturonate at pH 6.0 and 45 C and were active in the range of pH 4.0 to 9.0 and 10 to 60 C.