Microbial metabolism of 1,2‐propanediol studied by the Rumen Simulation Technique (Rusitec)

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Abstract
Experiments with the Rumen Simulation Technique (Rusitec) showed that 1,2-propanediol was metabolized efficiently by rumen microorganisms and that the main end-products of fermentation were propionic and 2-methylbutyric acids. Propionaldehyde and n-propanol were also formed as intermediate compounds. The effect of the diol on digestion of the basal diet appeared to be small with concentrate, or when the roughage was supplemented with additional N (urea). The decrease in the output of acetic and butyric acids was consistent with utilization of C2 units for synthesis of 2-methylbutyric acid. The fermentation of 1,2-propanediol resulted in little or no increase in the output of additional microbial matter. The distribution of radioactivity from [1-14C]1,2-propanediol confirmed that propionaldehyde and n-propanol were the primary products of metabolism of the diol and that the end-products were propionic and 2-methylbutyric acids, with very little labeling of microbial matter. Between 2-3% of radioactivity was found in gases and the specific radioactivity of CH4 was higher than that of CO2, particularly during the initial stages of incubation. Possible pathways in the degradation of 1,2-propanediol by rumen microorganisms are suggested and discussed in relation to similar reactions established in other systems.