Process Development Acetogens

Development of processes for production of acetic acid by the anaerobic acetogenic bacteria has focused mainly on fermentation of sugars. The advantage of these bacteria (such as C. thermoaceticum) is that they are homofermentative, with almost quantitative conversion of substrate to acetic acid. However, as outlined above (see section O Strain Improvement Acetogens ), they are sensitive both to high sugar concentration and to inhibition by acid conditions, resulting in limited acetic acid output (less than 20 g/1) in batch culture. 

The acid-tolerant mutant of C. thermoaceticum ATCC49707 (see section O Strain Improvement Acetogens ) when grown in batch culture with pH controlled at pH 6.3-6.8 showed a much improved acetic acid output of 30 0 g/1 

Comparison of experimental bioreactors for acetate production from sugars by acetogenic Clostridia 

Bioreactor and process Acetic acid output (g/1) Acetic acid productivity (g/l-h) Stable operation (days) References 

Cell recycle continuous, hollow fiber filtration 25-45 0.4-1.7 54 Parekh and Cheryan (1994a) 

---