Consolidated bioprocessing of plant biomass to polyhydroxyalkanoate by co-culture of Streptomyces sp. SirexAA-E and Priestia megaterium.

Polyhydroxyalkanoate (PHA) production from plant biomass is an ideal way to realize sustainable PHA-based bioplastic. The present study demonstrated consolidated bioconversion of plant biomass to PHA by co-culturing two specialized bacteria, cellulolytic Streptomyces sp. SirexAA-E and PHA producing Priestia megaterium. In monoculture, S. sp. SirexAA-E does not produce PHA, while P. megaterium did not grow on plant polysaccharides. The co-culture showed poly(3-hydroxybutyrate) (PHB) production using purified polysaccharides, including cellulose, xylan, mannan and their combinations, and plant biomass (Miscanthus, corn stalk and corn leaves) as sole carbon sources, confirmed by GC-MS. The co-culture inoculated with 1:4 (v/v) ratio of S. sp. SirexAA-E to P. megaterium produced 40 mg PHB/g Miscanthus using 0.5% biomass loading. Realtime PCR showed ∼85% S. sp. SirexAA-E and ∼15% P. megaterium in the co-culture. Thus, this study provides a concept of proof for one-pot bioconversion of plant biomass into PHB without separate saccharification processes.