Table 2.
A comparison of research cases on the synthesis of pyrazines using different cheap carbon sources.
| Carbon source type | Pretreatment/processing method | Key process | Target product | Yield | Costs | References |
|---|---|---|---|---|---|---|
| Distiller 's grains | Dilute acid pretreatment; Fermentated by B. subtilis TTMP20. | Optimization of detoxification conditions for distiller's grains hydrolysate. | TTMP | 705.27 mg/L | 34-66 $/t | (Gan et al., 2023; Zheng et al., 2024) |
| Corncob | Alkali-treated; Fermentated by B. subtilis IPE5-4-UD-4. | Composite mutation;Isothermal simultaneous saccharification and fermentation. | Acetoin | 0.46 g/g | 50-30 $/t | (Jia et al., 2017; Zhang, 2023) |
| Ignocellulosic hydrolysates | Fermentated by engineered B. subtilis ZB02. | The overexpression of transporter (AraE) and key enzymes (XylA and XylB) enables it to utilize glucose, xylose and arabinose simultaneously. | Acetoin | 11.20 g/L | / | Zhang et al. (2016) |
| Sugarcane molasses | Fermentation after treatment with sulfuric acid; Soybean meal as nitrogen sources. | Knockout the key genes bdhA and acoA in the acetoin catabolism pathway. | TTMP | 1328.95 mg/L | 120 $/t | (Zhou et al., 2019; Li et al., 2023) |
| Okara hydrolysate | Batch fermentation and fed-batch fermentation; Fermentated by B. subtilis BSO3. | Knockout the key genes bdhA and acoA; overexpression of the arabinose transporter-encoding gene (araE). | TTMP | 5.33 g/L (Batch fermentation);13.37 g/L (Fed-batch fermentation) | 32-83 $/t | Li et al. (2023) |