History of the acetone-butanol-ethanol fermentation industry in China: development of continuous production technology.

The acetone-butanol-ethanol (ABE) fermentation industry in China was started in the early 1950s in Shanghai and expanded rapidly thereafter. At its peak, there were about 30 plants all over the country and the total annual production of solvents reached 170,000 tons. This large enterprise was compelled to complete shutdown at the end of the 20th century due to the rapid increase of petrochemicals. The success of the ABE industry in China had special features like the development of a continuous fermentation technology. Its main strategic considerations were as follows: maintaining maximal growth and acid production phase, adoption of multiple stages in the solvent phase to allow gradual adaptation to increasing solvent, and the incorporation of stillage to offer enough nutrients to delay cell degeneration. Due to the tremendous national demand for solvents, China has begun a new round of ABE fermentation research. It is expected that a new era in the ABE industry is on the horizon.

Bacterial type I glutamine synthetase of the rifamycin SV producing actinomycete, Amycolatopsis mediterranei U32, is the only enzyme responsible for glutamine synthesis under physiological conditions.

The structural gene for glutamine synthetase, glnA, from Amycolatopsis mediterranei U32 was cloned via screening a genomic library using the analog gene from Streptomyces coelicolor. The clone was functionally verified by complementing for glutamine requirement of an Escherichia coli glnA null mutant under the control of a lac promoter. Sequence analysis showed an open reading frame encoding a protein of 466 amino acid residues. The deduced amino acid sequence bears significant homologies to other bacterial type I glutamine synthetases, specifically, 71% and 72% identical to the enzymes of S. coelicolor and Mycobacterium tuberculosis, respectively. Disruption of this glnA gene in A. mediterranei U32 led to glutamine auxotrophy with no detectable glutamine synthetase activity in vivo. In contrast, the cloned glnA gene can complement for both phenotypes in trans. It thus suggested that in A. mediterranei U32, the glnA gene encoding glutamine synthetase is uniquely responsible for in vivo glutamine synthesis under our laboratory defined physiological conditions.