Production of poly-β-hydroxybutyrate (PHB) by Methylobacterium organophilum isolated from a methanotrophic consortium in a two-phase partition bioreactor

Abstract

The biodegradation of methane, a greenhouse gas, and the accumulation of poly-β-hydroxybutyrate (PHB) were studied using a methanotrophic consortium and an isolated strain thereof. The specific rates for methane consumption were 100 and 17 m g C H 4 g x − 1 h − 1 for the isolate and the consortium, respectively. Also the effect of including 10% (v v −1) of silicone oil in a two-phase partitioning bioreactor (TPPB) was assayed for the elimination of 1% methane in air stream. TPPB allowed a 33–45% increase of methane elimination under growing conditions. Nitrogen limitation was assayed in bioreactors to promote PHB production. Under this condition, the specific methane degradation rate remained unchanged for the consortium and decreased to 36 m g C H 4 g x − 1 h − 1 for the isolated strain. The accumulated PHB in the reactor was 34% and 38% (w w −1) for the consortium and the isolate, respectively. The highest productivity was obtained in the TPPB and was 1 .61 m g PHB g x − 1 h − 1 . The CZ-2 isolate was identified as Methylobacterium organophilum, this is the first study that reports this species as being able to grow on methane and accumulate up to 57% (w w −1) of PHB under nitrogen limitation in microcosm experiments.