New PROMICON research paves the way for more efficient PHB production strategies

Polyhydroxybutyrate (PHB) is a biopolymer whose versatile physicochemical properties enable its applications in different fields, such as packaging and medicine. However, industrial PHB production costs remain high due to reliance on "pure" microbial cultures, making it difficult for PHB to be price competitive with traditional plastics. Utilising microbial "mixed" cultures (microbiomes) for PHB production offers potential cost reductions by operating in open systems without sterilisation and using cheap by-products and waste streams as feed, thus aligning it with the circular economy concept.

In light of that, PROMICON partners from UPC – as part of their work in WP2 – aimed to set a strategy to enrich cyanobacteria PHB-producers in order to enhance this biopolymer production. A preprint on their work is available in bioarxiv and their work has subsequently been published in Algal Research. 

To enhance biopolymer production in microbiomes, PROMICON partners evaluated a novel methodology based on cycles of alternating cell growth and subsequent biopolymer accumulation. One of the challenges considered in the study was maintaining productive cyanobacterial cultures for long-term bioproduct generation. Thus, PROMICON researchers conducted their experiment over 197 days. Despite challenges, such as the presence of green algae potentially reducing PHB production, their microbiome yielded up to 22% dry cell weight (dcw) PHB. These findings emphasise the importance of culture composition and suggest the potential application of their methodology to boost PHB production in robust cyanobacteria-rich microbiomes.

Confocal Laser Scanning Microscopy image of Synechocystis sp. cells. PHB granules are clearly detected as bright dots within the cells.