Table 3.

Comparison of B. subtilis and E. coli as chassis for pyrazines biosynthesis.

Attribute	B. subtilis	E. coli
Native pathway capacity	High (TTMP/alkylpyrazines via acetoin)	None (requires full heterologous pathway)
Max. reported titer	13.37 g/L TTMP (Li et al., 2023)	2.90 g/L 2,5-DMP (Liu et al., 2024)
Metabolic flexibility	Limited (alkylpyrazines dominant)	High (engineered for various pyrazines)
Key engineering targets	Precursor retention (bdhA, acoA)	Pathway assembly + Cofactor balancing (NADH/NADPH)
Process scalability	Robust in waste-based media (e.g., molasses)	Demands defined media; Sensitive to inhibitors