Precursor supply strategy for tetramethylpyrazine production by bacillus subtilis on solid-state fermentation of wheat bran.

Tetramethylpyrazine (TTMP) is a widely used flavoring additive with a nutty and roasted taste. Solid-state fermentation (SSF) of wheat bran for producing TTMP was studied with Bacillus subtilis CCTCC M208157, which was an exogenous precursor-independent TTMP-producing strain. Factors influencing endogenous precursor supply and TTMP formation in this strain were investigated. According to the findings, glucose and diammonium phosphate contributed to TTMP production but excess salts caused an inhibition on cell growth and TTMP formation. Then a two-step supply strategy was applied: 10 % glucose was added at the beginning of the process to allow acetoin formation, which was the precursor of TTMP, while 3 % diammonium phosphate was added only after acetoin accumulation reached its maximum. By applying this strategy, acetoin increased from 5.44 to 13.2 g/kg dry substrate (kgds), and consequently the yield of TTMP increased by 6.8 folds from 0.44 to 3.01 g/kgds. This was the first report of using a two-step supply strategy for TTMP production by SSF, which proved to be conducive to TTMP production in this strain.