Control of acetic acid concentration by pH-stat continuous substrate feeding in heterotrophic culture phase of two-stage cultivation of Alcaligenes eutrophus for production of P(3HB) from CO2, H2, and O2 under non-explosive conditions
✍ Scribed by Toshikazu Sugimoto; Takeharu Tsuge; Kenji Tanaka; Ayaaki Ishizaki
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 179 KB
- Volume
- 62
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
A-two stage culture method of hydrogenoxidizing bacterium, Alcaligenes eutrophus, is used to produce poly-D-3-hydroxybutyrate, P(3HB) from CO 2 , O 2 , and H 2 without using a very high oxygen transfer rate while maintaining the O 2 concentration in gas phase below 6.9 (v/v)% to prevent detonation of the gas mixture. The two-stage method consists of a heterotrophic culture using fructose as carbon source for exponential cell growth and an autotrophic culture for P(3HB) accumulation. We investigated the use of acetic acid as a cheaper carbon source than fructose for the heterotrophic culture in the two-stage method. However, the acetate concentration in the culture system must be maintained at 1.0 g и dm -3 since its inhibitory effect on the cell growth is very strong. Then, high cell density cultivation of A. eutrophus was investigated by pH-stat continuous feeding of acetic acid to control acetate concentration. As a result, acetate concentration was automatically maintained around 1.0 g и dm -3 by using a feed with a composition in CH 3 COOH/CH 3 COONH 4 /KH 2 PO 4 molar ratio of 5:1:0.084. Cell concentration increased to 48.6 g и dm -3 after 21 h of cultivation. The cell mass grown in the fedbatch culture on acetic acid was useful for P(3HB) production from CO 2 in the subsequent autotrophic culture stage.