Pilot-scale production of mcl-PHA by Pseudomonas citronellolis using acetic acid as the sole carbon source

Expanding the utilization of alkane mixtures: Enhancing medium chain length polyhydroxyalkanoate production in Pseudomonas resinovorans through alkane monooxygenase overexpression

Medium chain length Polyhydroxyalkanoate (mcl-PHA) is a biodegradable bioplastic material with promising applications in various fields, including the medical, packaging, and agricultural industries. This mcl-PHA can be biosynthesized by microorganisms from various carbon sources, and notably, it can also be produced from alkane mixtures contained in pyrolysis oil derived from low-grade waste plastics. In this study, Pseudomonas resinovorans was engineered to overexpress alkane monooxygenase from Lysinibaillus fusiformis JJY0216, enhancing its ability to utilize alkanes as carbon sources and thereby increasing mcl-PHA production. The engineered strain, P. resinovorans JJY01, demonstrated a notable increase in cell dry weight (CDW) to 0.97 g/L and mcl-PHA production to 0.33 g/L from an optimized alkane mixture, achieving a 1.7-fold enhancement compared to the wild type. The PHA content reached 39.5 %, which is 3.1 times higher than the wild type. Further optimization through fed-batch cultivation resulted in P. resinovorans JJY01 achieving 5.65 g/L of CDW, 3.07 g/L of PHA, and a PHA content of 57.5 % within 96 h. In addition, produced mcl-PHA were characterized through various analytical techniques to assess their physical properties and monomer compositions, highlighting the potential of mcl-PHA produced by P. resinovorans JJY01 as a candidate for medical-grade biopolymers.

Pilot scale polyhydroxyalkanoates biopolymer production using pure cultures: current status and future opportunities

The development and commercialization of bio-based and biodegradable polyhydroxyalkanoates (PHAs) biopolymers could be crucial for the transition toward a sustainable circular economy. However, despite potential traditional and novel applications in the packaging, textiles, agriculture, automotive, electronics, and biomedical industries, the commercialization of PHAs is limited by their current market competitiveness. This review provides the first critical assessment of the current pure culture pilot-scale PHA literature, which could be crucial in translating promising laboratory-scale developments into industrial-scale commercial PHA production. It will also complement reviews of mixed microbial cultures currently dominating pilot-scale PHA literature. Pure culture fermentations could provide advantages, such as ease of characterizing microbial producers' behavior, higher PHA productivities, and better alignment with existing PHA commercialization and industrial biotechnology approaches. Key aspects, including producer organisms, fermentation volumes and schemes, control schemes, optimization, and properties of the polymers produced, are discussed in-depth, to elucidate important trends, achievements, and knowledge gaps. Furthermore, specific ways for future pilot-scale studies to help address current PHA commercialization challenges are also identified. The insights, and recommendations provided will be extremely beneficial for the future development of PHA production, at both pilot and commercial scales, whilst also being beneficial to the production of other microbial polymers and industrial biotechnology as a whole.

Acid hydrolysis of Solanum tuberosum periderm for accumulation of polyhydroxyalkanoates in Pseudomonas putida MTCC 2475

Polyhydroxyalkanoates are a class of biodegradable, biocompatible polymers composed of polyesters of R-hydroxyalkanoic acids and deposited intracellularly by a variety of microorganisms which have potential to serve as alternative to commercial plastic. Bioplastics are gaining attention due to sustainability, biodegradability, biocompatibility, and lower carbon footprint. Nevertheless, the commercialization of PHA is predominantly hindered by the elevated production expenses arising primarily from the use of a pure sugar substrate. Our study has established a feasible method for bioplastic formation applying Pseudomonas putida MTCC 2475 and Solanum tuberosum periderm as a carbon source. To optimize the sugar yield response surface methodology was used, which released 69.34% ± 0.25% reducing sugar. PHA production experiments were performed in hydrolysate containing media as well as commercial sugar containing mineral salt media. After 48 h of fermentation of using this sugar, a biomass concentration of 2.19 gL-1, with a PHA production of 0.60 gL-1 (28.71% ± 0.55%) was obtained which was comparatively similar with synthetic media (2.56 gL-1 cell dry weight and 29.97% ± 0.45% PHA). Furthermore, the monomers of PHA produced by hydrolysate were characterized using Gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance. This investigation has identified three distinct monomers of medium-chain PHAs, namely, methyl 3-Hydroxydodecanoate, 3-Hydroxytetradecanoate, and Hexadecanoic acid 3-Hydroxy methyl esters. Hence this study concludes a sustainable production of bioplastics from S. tuberosum periderm waste.