Summary
The effect of the ratio of methanol to ammonia, in the feeding solution the C/N ratio, on microbial PHB production was investigated. A constant C/N ratio regulated both the PHB content and the specific rate of PHB production. The results indicated that to produce the maximum PHB effectively in a short time the C/N ratio should be controlled automatically according to the increase in PHB content. Variation of the PHB content was estimated by tracing the timecourse of CO2 concentration in exhaust gas. When the cell concentration reached 70 g/l, C/N ratio was gradually increased from the initial C/N ratio of 10 (mol methanol/mol ammonia). At 121 h, concentration of PHB reached 136 g/l, which was the maximum level so far obtained. The reaction time was considerably shortened compared with our previous study (175 h). Furthermore, PHB concentration reached 149 g/l at 170 h and total cell concentration became 233 g/l. PHB yield from methanol was 0.20 (g PHB/g methanol), which was also superior to the previous result of 0.18.
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Suzuki, T., Yamane, T. & Shimizu, S. Mass production of poly-β-hydroxybutyric acid by fed-batch culture with controlled carbon/nitrogen feeding. Appl Microbiol Biotechnol 24, 370–374 (1986). https://doi.org/10.1007/BF00294592
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DOI: https://doi.org/10.1007/BF00294592