Production of poly-β-hydroxybutyrate by Alcaligenes eutrophus on different carbon sources

Abstract

Poly-β-hydroxybutyrate was produced in shake cultures by Alcaligenes eutrophus H16 on fructose, xylose, and fumaric, itaconic, lactic and propionic acids in a three-stage process. The maximum polymer concentration of 6.9 g l⁻¹ (69% of cell dry matter) was obtained with 20g l⁻¹ of fructose with a volumetric productivity of about 0.22 g l⁻¹ h⁻¹ at 24h. Up to about 3 g l⁻¹ (about 50% of cell dry matter) of polymer was also produced on lactic and propionic acids as the sole carbon source during the production phase. In multivatiate optimization employing an orthogonal 2³-factorial central composite experimental design with fructose as the substrate in a single-stage process, the optimal initial fructose concentration decreased from 35 g l⁻¹ to 24 g l⁻¹ when the incubation time was increased from about 35 h to 96 h. The optimal shaking speed range was 90–113 rpm.