High-cell-density poly (3-hydroxybutyrate) production from sucrose using Burkholderia sacchari culture in airlift bioreactor

Abstract

Burkholderia sacchari IPT 189 poly (3-hydroxybutyrate) (P3HB) production in airlift bioreactor were investigated in batch and fed-batch culture using sucrose as carbon source. In batch experiments it was observed that during the growth phase B. sacchari IPT 189 might display exponential growth even at very low carbohydrate concentration, as long as NH 4 + concentration was above 190 mg l −1. The onset of accumulation phase took place when NH 4 + concentration dropped below this value and continued as long as carbohydrate was in excess, even with dissolved oxygen concentration at 0.0% of air saturation. In the fed-batch experiments, nitrogen limitation was used to induce P3HB biosynthesis in a two-phase process. In the first phase, an initial batch followed by a limited sucrose fed regime led to a growth with low-P3HB-content (less than 13%) and up to 60 g l −1 of biomass concentration in c.a. 25 h. In the second phase, nitrogen concentration limitation induced P3HB accumulation up to 42%, raising the biomass concentration to c.a. 150 g l −1. Calculated parameters for the experiments were P3HB productivity = 1.7 g l −1 h −1 and P3HB yield factor from sucrose = 0.22 g g −1.