|TITLE||Development of technique for producing valuable chemical material by hydrogen
(Joint Program to Promote Technological Development with the Private Sectors)
This development has two objects. One is developing a technique of accumulation of poly-β-hydroxybutyrate (PHB), which would be a raw material for biodegradable plastic, by autotrophic culture of hydrogen-oxidizing bacteria. The microorganism used was Alcaligenes eutrophus ATCC 17697T. The other is substantiating a stability of the fermentation by a pilot plant including an air lift fermentor. The numerical values of targets of accumulation yield of PHB and cell product yield were 60% and 3g/L・hr, respectively.
Four studies are as follows.
1. Design, construction, installment of a 2L-fermentation system for fundamental experiments and a 400L-fermentation system for industrial application
2. Explosion free fermentation system
3. Highly efficient accumulation of PHB
4. Test of stable fermentation and evaluation
The explosion free fermentation systems were established. These systems allowed operation safety and continuous operation.
The investigation by using 2L-fermentation system provided optimum conditions for efficient culture and accumulation of PHB.
The method of evaluating each culture by means of some determinations was confirmed, and the possibility of developing a practical continuous fermentation system was evaluated by using 400L-fermentation system. It was consequently presumed that repeated batch culture can be applied for industry. The technique of fermentation operation for industrial large plant was established.
The accumulation yield of PHB reached 70%. On the other hand, cell product yield reached even as low as 1g/L・hr. However, it is possible to increase cell product yield by using gas absorption column. The effect of pressure in a fermentor that increase dissolved gas contributed to increasing growth rate in its early stage. Consequently, it suggested that gas adsorption and pressure were necessary to achieve objects.