Pyrazine production by Bacillus subtilis

2,5-Dimethylpyrazine (2,5-DMP) and tetramethylpyrazine (TTMP) were produced using Bacillus subtilis IFO 3013 grown in solid substrate conditions using soya flour, suspended in water. Optimization studies, carried out using preceding results obtained on ground soybeans, showed that the conditions of the hydrothermal processing involved in medium sterilization were of critical importance for 2,5-DMP synthesis in L-threonine enriched substrates. Also, further feeding of the medium with acetoin and ammonium salts allowed subsequent TTMP production. As a result, 3.5 g/L 2,5-DMP were obtained after 24 h cultivation, and ca. 1 g/L TTMP after 4 days.