2,5-Dimethylpyrazine (2,5-DMP) and tetramethylpyrazine (TTMP) were produced using Bacillus subtilis IFO 3013 grown in solid substrate conditions using ground soybeans suspended in water. Optimization studies showed that the best way to produce the two above aroma compounds involved massive enrichment of the medium with L-threonine and acetoin, The amino acid allowed 2,5-DMP formation and was added at 40 g/l at the beginning of a process, while acetoin was the precursor of TTMP and had to be added at 60 g/l only after 2,5-DMP production was terminated. The optimal cultivation temperature was 40 degrees C, pH had to be monitored at 7.5, and aeration rate had to be higher than 0.1 VVM with a volu metric oxygen tranfer coefficient k(L)a close to 180 h(-1) . These conditions allowed recovery of 2 g/l total pyrazines, that demonstra ted the efficiency of this approach.