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bioRxiv · 10.1101/2025.11.12.688118

Bioplastic Production Potential of Azospira suillum PS: Growth-Associated PHB Production Under Aerobic and Anaerobic Conditions

Meier, D. A. O.·Glazer, B.·Lanclos, V. C.·Carlson, H. K.·Coates, J. D.
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Abstract

Plastics are indispensable in modern society, yet less than 10% of the 380 million tons produced annually are recycled. This accumulation of non-degradable waste has intensified the search for sustainable alternatives. Polyhydroxyalkanoates (PHAs), particularly polyhydroxybutyrate (PHB), are biodegradable polymers produced by microorganisms. Here, we investigate the capacity of Azospira suillum PS, a model facultative perchlorate-reducing bacterium, to synthesize PHB. We show that unlike most organisms, PHB production is growth-associated both aerobically, and anaerobically with perchlorate as an electron acceptor under moderate nitrogen deplete conditions. Genomic analysis revealed four phaC homologs, with one, phaC4, co-localized with phaB and phaR, suggesting a conserved operon. While three of the phaC genes were successfully deleted, phaC4 could not be disrupted, indicating an essential role for growth. Redox profiling revealed a positive correlation between PHB accumulation and NADPH/NADP+ ratios, supporting the role of cytoplasmic reducing equivalents in PHB synthesis. This study presents the first demonstration of PHA production under perchlorate-respiring conditions and one of the few documented cases of growth-associated PHA synthesis. It offers new insights into the genetic and metabolic basis of PHB production in A. suillum PS, underscoring its potential as a platform organism for sustainable, growth-coupled bioplastic production.

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Meier, D. A. O., Glazer, B., Lanclos, V. C., Carlson, H. K., Coates, J. D.. 2025-11-12. Bioplastic Production Potential of Azospira suillum PS: Growth-Associated PHB Production Under Aerobic and Anaerobic Conditions. https://doi.org/10.1101/2025.11.12.688118

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