Influence of organic loading rate and solid retention time on polyhydroxybutyrate production from hybrid poplar hydrolysates using mixed microbial cultures

• Polyhydroxybutyrate was biosynthesized from poplar wood hydrolysates.
• Fed-batch bioreactors were seeded using mixed microbial cultures.
• Microbial community evolution was monitored using 16S rRNA Illumina sequencing.
• Actinobacteria, Alpha- and Beta-proteobacteria were dominant groups in bioreactors.

The aim of this study was to investigate the potential of using wood hydrolysates (enzymatically hydrolyzed from hybrid poplar) as substrate to produce polyhydroxybutyrate (PHB) using mixed microbial cultures. The optimal operational conditions for fed-batch bioreactors were 4 d solid retention time with an organic loading rate of 2.5 g/Ld. The maximum PHB accumulated was 27% of cell dry weight with a yield of 0.32 g/g (g PHB produced per g sugars consumed). Microbial community analysis was done at the genus level by 16S rRNA sequencing on an Illumina system and community evolution was observed among different samples and initial seed. Actinobacteria, Alpha- and Beta-proteobacteria were found to be the dominant groups in all the bioreactors. Several PHB-storing microorganisms were characterized belonging to Alpha- and Beta-proteobacteria.

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