The enzyme acetolactate decarboxylase (ALDC), which is used in the fermentation of beer, is produced by Bacillus subtilis containing the structural gene for ALDC production originating from a Bacillus brevis . ALDC and the glutaraldehyde-stabilized ALDC were subjected to a series of toxicological tests to investigate their safety. None of the ALDC preparations were mutagenic either in bacterial cultures (Ames test) or in mammalian cell cultures (mouse lymphoma assay) nor did they cause chromosomal damage (human lymphocyte assay). The test materials possessed no antimicrobial activity. To investigate the toxicological properties of ALDC, dietary concentrations of 200, 1,400, 10,000 ppm ALDC, or 10,000 ppm stabilized ALDC were given to rats continuously for 13 weeks. When given to pregnant rats at similar dose levels, no effect on the outcome of pregnancy was observed. The dietary concentration of 10,000 ppm corresponds to an intake of some 760 mg/kg/day, which represents approximately 120,000 times the estimated human intake. The toxicological investigations have proven ALDC to be a safe enzyme for use in fermentation of beer.