Robust strategy for bioplastic production from cyanobacteria-enriched microbiomes: insights from gene expression and population dynamics

In this study, four cyanobacteria-rich microbiomes were evaluated in terms of PHB synthesis over 168 days. Despite applying consistent environmental and cultivation conditions to the cultures, significant differences in biopolymer accumulation were observed, highlighting the influence of microbial community on PHB production. By overlapping PHB quantification data, DNA sequencing and RT-qPCR data, links between PHB content, microbial community, and gene expression could be detected. The high PHB content in CW1 microbiome was associated with upregulation of the phaC gene, involved in PHB synthesis, and glgp1, linked to glycogen catabolism. This suggested an interaction between PHB and glycogen pathways that supports higher PHB accumulation. In contrast, lower PHB production in CW2 microbiome (a representative example of microbiome with reduced PHB content) correlated with the overexpression of gltA, a gene involved in the TCA cycle, which may divert metabolic resources away from PHB synthesis. Moreover, variations in the relative abundance of Cyanobacteria and Alphaproteobacteria were observed across microbiomes. The stabilization of Alphaproteobacteria and Cyanobacteria relative abundances in CW1 were associated to high PHB content. The findings suggest that maintaining a balanced coexistence between these microbial groups may be critical for achieving optimal PHB production in cyanobacteria-enriched microbiomes. However, it is important to note that the specific mechanisms underlying this interaction remain unclear and further investigation is needed to elucidate the precise roles of each microbial group in PHB accumulation.

This work was supported by the European Union’s Horizon 2020 research and innovation programme under the grant agreement No 101000733 (project PROMICON). B.A.A. acknowledges the Agency for Management of University and Research (AGAUR) for her grant [FIAGAUR_2021]. L.S. thanks the financial support from the program of China Scholarships Council (No. 202308440158) J. N. acknowledges the support of SyCoSys project, TED2021-130689B-C33 funded by MCIN/ AEI/10.13039/ 501100011033 and the European Union “NextGenerationEU”/PRTR. E.G.F. would like to thank the European Union-NextGenerationEU, Ministry of Universities and Recovery, Transformation and Resilience Plan for her research grant [2021UPF-MS-12]. J.G. acknowledges the support provided by the ICREA Academia program. The authors would like to sincerely thank ADM Biopolis (Val` encia, Spain) for their assistance in performing the 16S rRNA gene amplification, and the Barcelona Research Center in Multiscale Science and Engineering (Barcelona, Spain) for their support with the confocal laser scanning microscopy.

Peer Reviewed

Postprint (published version)