Control of Ethyl Carbamate Formation in Wine From Arginine Degradation by

In the past term we have investigated the inhibitory effect of several energy sources on the degradation of arginine and the excretion of citrulline by malolactic bacteria. It was found that increasing sugar concentrations lead to a reduced arginine degradation rate. It is likely that the inhibition is mediated by the energy status of the bacterial cells, or more specifically by the intracellular concentration of ATP that may be increased when higher sugar concentrations are present in the medium. Citrulline excretion from arginine degradation was increased at high glucose concentrations, suggesting that more citrulline was built up intracellularly during arginine degradation. Therefore, an inhibition is likely to occur at the second enzymatic step responsible for the degradation of citrulline. Degradation pathway of arginine in malolactic bacteria. L-arginine + H20 ? >? L-citrulline + NFL,* (1) L-citrulline + Pi -< £?!£ >? L-ornithine + carbamyl-P (2) carbamyl-P + ADP < £K ^ ATP + C02 + NH/ (3) The ability of different malolactic bacteria to increase their growth by degrading arginine was further investigated with 2 lactobacilli and 2 oenococci. It was found that only one lactobacilli was able to increase its growth by degradation of arginine and only at pH values of 3.5 or more. However, under these conditions the growth advantage was considerable. A cheap and simple enzymatic method for quantification of arginine was evaluated. The test is an end-point method comparable to those offered by Boehringer Mannheim (now Roche) for many substrates and fills the gap between sophisticated apparative methods and the unspecific chemical methods that are still widely used.