Effects of aeration on the synthesis of poly(3-hydroxybutyrate) from glycerol and glucose in recombinant Escherichia coli

Abstract

Bioreactor cultures of Escherichia coli recombinants carrying phaBAC and phaP of Azotobacter sp. FA8 grown on glycerol under low-agitation conditions accumulated more poly(3-hydroxybutyrate) (PHB) and ethanol than at high agitation, while in glucose cultures, low agitation led to a decrease in PHB formation. Cells produced smaller amounts of acids from glycerol than from glucose. Glycerol batch cultures stirred at 125 rpm accumulated, in 24 h, 30.1% (wt/wt) PHB with a relative molecular mass of 1.9 MDa, close to that of PHB obtained using glucose.

FIG. 1.

Growth and PHB accumulation by strain KP24KP grown with shaking in 250-ml flasks in MYA medium supplemented with 3% (wt/vol) glucose (triangles) or glycerol (circles) under the four culture conditions indicated in the figure. All experiments were conducted at least twice, and results shown are mean values. Standard deviations were <5% of the means.

FIG. 2.

Fermentation profiles of strain K24KP grown on glycerol or glucose in 24-h bioreactor cultures at low (A) or high (B) aeration. Cell dry weight (CDW) in glycerol cultures, open triangles; CDW in glucose cultures, closed triangles; PHB content in glycerol cultures, open circles; PHB content in glucose cultures, closed circles. All experiments were conducted at least twice, and results shown are mean values. Standard deviations were <5% of the means.