Researchers from the Biochemical Engineering Lab at UCIBIO-NOVA have published a new study in the journal Bioresource Technology exploring how carbon dioxide (CO₂) influences the way certain bacteria produce a type of biodegradable plastic. The study, titled "Influence of inorganic carbon on purple phototrophic bacteria polyhydroxyalkanoates production under high reductive stress environment", was developed by Juliana Roda Almeida, Maria Ascensão Reis, and Joana Costa Fradinho.
The research focused on a group of bacteria known as Purple Phototrophic Bacteria (PPB), which are capable of producing polyhydroxyalkanoates (PHA), an internal biopolymer with thermoplastic properties that can be used to produce fully biodegradable plastics.
A natural material that has plastic-like properties and can break down in the environment, making it a promising alternative to traditional plastics. The researchers aimed to understand how the availability of CO₂ affects both the diversity of the bacterial cultures and how efficiently they produce PHA. According to the team, “with decreasing CO₂ availability, the culture decreased its microbial diversity, and became dominated by the purple bacteria Rhodopseudomonas palustris, yet maintained similar PHA content across different CO₂ availabilities.”
The authors also observed a trade-off between growth and plastic production: “when CO₂ was present, growth was promoted over PHA production, and when CO₂ was limited, a preference for PHA production was observed,” explains Joana Costa Fradinho, senior researcher in the Biochemical Engineering Lab and co-leader of the study.
This discovery may help improve the use of organic waste in producing biodegradable plastics. Although PHA is considered an environmentally friendly alternative to conventional plastics, it remains more expensive to produce. Using low-cost waste streams combined with controlled CO₂ levels could make PHA production more efficient and economically viable.
The study highlights CO₂ tuning as a potential growth-controlling strategy to boost phototrophic PHA production using reduced feedstocks, offering new insights for the development of sustainable materials.
Original article:
Influence of inorganic carbon on purple phototrophic bacteria polyhydroxyalkanoates production under high reductive stress environment
Juliana Roda Almeida, Maria Ascensão Miranda Reis, Joana Costa Fradinho
Bioresource Technology, 428, 132462
DOI: 10.1016/j.biortech.2025.132462
(link to: https://doi.org/10.1016/j.biortech.2025.132462)