Ayaaki Ishizaki, Naohiko Taga, Toshihiro Takeshita, Toshikazu Sugimoto,
Takeharu Tsuge, and Kenji Tanaka

Department of Food Science and Technology, Faculty of Agriculture,
Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812, Japan

Fermentative production of biodegradable plastic material, poly-D-3- hydroxybutyrate, P(3HB) from CO2 or agricultural wastes is expected to contribute to the solution of global environmental pollution problems. The practical cultivation systems to produce P(3HB) from CO2, H2 and O2 by hydrogen-oxidizing bacterium were developed by maintaining O2 concentration in gas phase below the lower limit for explosion. P(3HB) productivity was increased by improving gas mass transfer with the use of air-lift fermentor and the addition of 0.05 %CMC to the culture medium. P(3HB) was also produced from xylose via L-lactate by two-stage culture method using Alcaligenes eutrophus and Lactococcus lactis 10-1. P(3HB) productivity was increased by a pH-stat fed-batch culture method with feeding the substrate solution so as to control L-lactate concentration at very low level.

Polyhydroxyalkanoates, PHAs are potential raw materials for manufacturing biodegradable plastics(l). Alcaligenes eutrophus is a hydrogen-oxidizing bacterium that is able to grow autotrophically using H2, O2 and CO2 and heterotrophically using organic acids as substrate with the accumulation of poly-D-3-hydroxybutyric acid, P(3HB) in the cell under nutrient-limited conditions(Fig. l). The growth rate of this hydrogen-oxidizing bacterium is much higher than that of other autotrophs such as photosynthetic organisms and hence the bacterium has the potential to be used in industrial processes. Production of P(3HB) from CO2 or organic acids derived from agricultural wastes by A. eutrophus, could contribute to the solution of two environmental pollution problems of increased CO2 levels in the atmosphere and that of the disposals of non-biodegradable plastic waste. Here, we describe a strategy and system set-up for fermentative production of P(3HB) from CO2 and agricultural waste materials.

© 1997 American Chemical Society