New strategy for bioplastic and exopolysaccharides production: Enrichment of field microbiomes with cyanobacteria

Abstract

Seven photosynthethic microbiomes were collected from field environmental samples to test their potential in polyhydroxybutirate (PHB) and exopolysaccharides (EPS) production, two alternatives to chemical-based polymers. Microscope observations together with microbial sequence analysis revealed the microbiome enrichment in cyanobacteria after culture growth under phosphorus limitation. PHB and EPS production was studied under three culture factors (phototrophy, mixotrophy and heterotrophy) by evaluating and optimizing the effect of three parameters (organic and inorganic carbon and days under light:dark cycles) by Box-Behnken design. Results showed that optimal conditions for both biopolymers synthesis were microbiome-dependent; however, the addition of organic carbon boosted PHB production in all the tested microbiomes, producing up to 14%dcw PHB with the addition of 1.2 g acetate L-1 and seven days under light:dark photoperiods. The highest EPS production was 59 mg L-1 with the addition of 1.2 g acetate L-1 and four days under light:dark photoperiods. The methodology used in this article is suitable for enriching microbiomes in cyanobacteria, and for testing the best conditions for bioproducts synthesis for further scale up.

Bioplastic production by harnessing cyanobacteria-rich microbiomes for perpetual synthesis

“…We started the study by inoculating two photobioreactors (PBRs) with 100 mg volatile suspended solids (VSS)·L -1 of microbiome R3 obtained in 16 . The study began with the growth phase of the conditioning cycle (Supplementary Fig.…”

“…Two microbiomes isolated in 16 , named R3 and UP, were used as the inoculum for 3 L glass cylindrical photobioreactors (PBRs) of 2.5 L working volume (Supplementary Fig. 17).…”

Species composition determines bioplastics production in photosynthetic microbiomes: strategy to enrich cyanobacteria PHB-producers

“…Consequently, to avoid green microalgae and favour cyanobacteria growth, P concentration at the beginning of each growth phase was xed at 0.1 mg•L − 1 . Note that the biomass used as inoculum for the PBRs had been kept in modi ed BG-11 medium with a P concentration of 0.5 mg•L − 1 (24). The P concentration set at the beginning of the conditioning period was 1 mgP•L − 1 to sustain cell growth; however, we assumed that this value was too high and P stopped being growth-limiting for green algae.…”

“…A mixed culture enriched with cyanobacteria would in effect combine the aforementioned advantages of working with microbiomes and cyanobacteria, potentially overcoming the production rates obtained by cyanobacteria monocultures up to now. Nevertheless, to the authors' knowledge, photosynthetic microbiomes enriched with cyanobacteria have only been tested for PHB production in (22)(23)(24), obtaining a PHB production up to 14%dcw PHB (24). In (24) the effect of the number of days under light and the presence of inorganic and organic carbon on PHB production by a photosynthetic microbiome was evaluated.…”

“…Nevertheless, to the authors' knowledge, photosynthetic microbiomes enriched with cyanobacteria have only been tested for PHB production in (22)(23)(24), obtaining a PHB production up to 14%dcw PHB (24). In (24) the effect of the number of days under light and the presence of inorganic and organic carbon on PHB production by a photosynthetic microbiome was evaluated. Outcomes revealed that the addition of an organic carbon source (acetate) greatly triggered biopolymer synthesis and reactors could be under dark during PHB production.…”