Tailor‐made PAT platform for safe syngas fermentations in batch, fed‐batch and chemostat mode with Rhodospirillum rubrum

Abstract

SummaryRecently, syngas has gained significant interest as renewable and sustainable feedstock, in particular for the biotechnological production of poly([R]‐3‐hydroxybutyrate) (PHB). PHB is a biodegradable, biocompatible polyester produced by some bacteria growing on the principal component of syngas, CO. However, working with syngas is challenging because of the CO toxicity and the explosion danger of H2, another main component of syngas. In addition, the bioprocess control needs specific monitoring tools and analytical methods that differ from standard fermentations. Here, we present a syngas fermentation platform with a focus on safety installations and process analytical technology (PAT) that serves as a basis to assess the physiology of the PHB‐producing bacterium Rhodospirillum rubrum. The platform includes (i) off‐gas analysis with an online quadrupole mass spectrometer to measure CO consumption and production rates of H2 and CO 2, (ii) an at‐line flow cytometer to determine the total cell count and the intracellular PHB content and (iii) different online sensors, notably a redox sensor that is important to confirm that the culture conditions are suitable for the CO metabolization of R. rubrum. Furthermore, we present as first applications of the platform a fed‐batch and a chemostat process with R. rubrum for PHB production from syngas.

A Review on Established and Emerging Fermentation Schemes for Microbial Production of Polyhydroxyalkanoate (PHA) Biopolyesters

“…These calculations are based on a biorefinery concept using switch grass as feedstock for syngas production and generating bio-hydrogen as a marketable by-product of this process; according to these authors, the fermentation process should be carried out in CSTRs [118]. Karmann and colleagues demonstrated a tailored platform for safe production of PHB from syngas using Labfors (Infors, Basel, Switzerland) STRs, which can be operated in fed-batch and chemostat mode; the authors underlined the importance of safety measures to overcome the risks connected to CO as toxic substrate and biohydrogen as a precarious co-product and online analytical tools to make PHA production technologically feasible [119]. More recently, heterologous expression of PHA synthase genes in R. rubrum was studied by Klask and colleagues in order to enhance PHA productivity, and to extend the range of types of PHA accessible by this strain.…”

Switching from petro-plastics to microbial polyhydroxyalkanoates (PHA): the biotechnological escape route of choice out of the plastic predicament?

“…Besides measuring devices to control gas supply and consumption, this platform contained an in-line flow cytometer to determine the biomass concentration and intracellular PHA fraction. The platform was used in fedbatch and continuous syngas-based PHA production processes with R. rubrum (106).…”

Chemical and Biochemical Engineering Approaches in Manufacturing Polyhydroxyalkanoate (PHA) Biopolyesters of Tailored Structure with Focus on the Diversity of Building Blocks

“…25 In particular, the use of C1-compounds like CO 2 , syngas, or methanol for PHA production is currently attracting increasing attention. [26][27][28][29][30] Beside the raw material aspect, downstream processing to recover PHA from microbial biomass in an efficient and environmentally sound fashion constitutes another crucial aspect of the PHA production chain. Here, solvent-based techniques for PHA extraction, enzymatic, chemical, and mechanical methods for disintegration of non-PHA biomass are exhaustively summarized in current review articles, all of these methods displaying shortcomings either in economic terms, environmental, and safety aspects, recovery efficiency, product purity, or scalability; this clearly indicates that PHA recovery displays a crucial aspect in making PHA market-fit.…”