Production of a newly discovered PHA family member with an isobutyrate-fed enrichment culture

Abstract

Using microbial enrichment cultures for the production of waste-derived polyhydroxyalkanoates (PHAs) is a promising technology to recover secondary resources. Volatile fatty acids (VFAs) form the preferred substrate for PHA production. Isobutyrate is a VFA appearing in multiple waste valorization routes, such as anaerobic fermentation, chain elongation, and microbial electrosynthesis, but has never been assessed individually on its PHA production potential. This research investigates isobutyrate as sole carbon source for a microbial enrichment culture in comparison to its structural isomer butyrate. The results reveal that the enrichment of isobutyrate has a very distinct character regarding microbial community development, PHA productivity, and even PHA composition. Although butyrate is a superior substrate in almost every aspect, this research shows that isobutyrate-rich waste streams have a noteworthy PHA-producing potential. The main finding is that the dominant microorganism, a Comamonas sp., is linked to the production of a unique PHA family member, poly(3-hydroxyisobutyrate) (PHiB), up to 37% of the cell dry weight. This is the first scientific report identifying microbial PHiB production, demonstrating that mixed microbial communities can be a powerful tool for discovery of new metabolic pathways and new types of polymers. Key points • PHiB production is a successful storage strategy in an isobutyrate-fed SBR • Isomers isobutyrate and butyrate reveal a very distinct PHA production behavior • Enrichments can be a tool for discovery of new metabolic pathways and polymers Graphical abstract

Production of medium‐chain‐length PHA in octanoate‐fed enrichments dominated by Sphaerotilus sp.

“…For the accumulation experiments, a gap in the mass balance developed over time, resulting in an average closure of 66.5 ± 13%. Although these gaps have been observed in accumulation experiments of previous research (Marang et al, 2016; Vermeer et al, 2022), the gaps in this study are larger. A possible explanation for the large size of these gaps forms the feeding method during the accumulation which entails the addition of undiluted octanoic or hexanoic acid.…”

Analysis of Bacterial Diversity in Different Types of Daqu and Fermented Grains From Danquan Distillery

“…The dominant microbe Comamonas sp. was linked to the yield of a unique PHA member poly(3-hydroxyisobutyrate) with an isobutyrate-fed enrichment culture (Vermeer et al, 2022 ). Comamonas played a dominant role in tetracycline hydrochloride degradation and power generation in a microbial fuel cell (Zhang et al, 2021 ).…”

Structural variability, implementational irregularities in mathematical modelling of polyhydroxyalkanoates (PHAs) production—A state‐of‐the‐art review

“…Metabolic model has also been used to explore the composition of PHA if a key substrate is replaced with a structural analogue. For example, the addition of isobutyrate to that of the butyrate‐based metabolic model for PHA production led to the discovery of a new PHA monomer, that is, poly(3‐hydroxyisobutyrate) (Vermeer et al, 2022). An MFA of the TCA for polyhydroxybutyrate (PHB) production in recombinant Escherichia coli suggests increasing flux of acetyl CoA/CoA ratio (with a response coefficient of 0.7) favors PHB production.…”