Biosynthesis of poly(3-hydroxybutyrate) by N,N-dimethylformamide degrading strain Paracoccus sp. PXZ: A strategy for resource utilization of pollutants

Deciphering the operation efficiency and fermentation model in mixed microbial cultures system for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) synthesis

The polyhydroxyalkanoates (PHAs) synthesis craft by using diversified organic acids from anaerobic fermentation was restricted due to the poor compatibility and uncertain biopolymer types. Odd-chain VFAs favor the accumulation of co-polyesters. In this study, propionic and valeric acids were utilized as substrates for mixed microbial cultures (MMC) acclimation, in the expectation of synthesizing poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with exceptional properties. Bioreactors using propionic acid and valeric acid as carbon substrates are defined as MMC-P and MMC-V, respectively. The acquisition of core PHAs communities was conducted under a feast-famine model, characterized by elevated carbon-nitrogen ratios (C/N) and increased organic loading. The optimum PHBV reached 616.47 mg L-1 (MMC-P, C/N = 60) and 406.68 mg L-1 (MMC-V, C/N = 80), accordingly. Allosphingosinicella, Labilithri, Stenotrophomonas, Brevundimonas, Parvibaculum, Azospirillum, and Hydrogenophaga were identified as the core PHBV fermentation consortium. The functional enzymes related to fatty acids β-oxidation and PHBV synthesis were concentrated. Four categories of PHAs synthases have been targeted for the production of multiple biopolymers. This study presented a technical reference for a convenient biomanufacturing process for efficient utilization of odd-chain organic waste.

Biorefinery of sugarcane molasses for poly(3-hydroxybutyrate) fermentation and genomic elucidation of metabolic mechanism using Paracoccus sp. P2

Biorefining sugarcane molasses to produce polyhydroxyalkanoates (PHAs) is an anticipated paradigm for replacing petroleum-based plastics. Nevertheless, there exists a deficiency in excellent chassis and genome resolution for the synthesis of poly(3-hydroxybutyrate) (PHB), which is a typical representative of PHAs. In this study, successive enrichment domestication was employed to screen PHB producers. The isolated species was defined as Paracoccus sp. P2 through taxonomic analysis. Then, a variety of nutrient substrates and physicochemical parameters were tailored to enhance the fermentation capacity. The maximum production of bio-polyester was 4.4 g·L-1, corresponding to a yield of 0.37 g-PHB·g-1-glucose. The concentration of PHB produced from 30 g·L-1 sugarcane molasses was 3.9 g·L-1, indicating a comparable fermentation performance. Furthermore, three-step condensation of acetyl-CoA and de novo synthesis of fatty acids were identified as the primary PHB accumulation pathways. The fermentation performance and genome investigation were compared with Paracoccus genus. The effective production of Paracoccus sp. P2 might be attributed to its efficient substrate conversion capacity and abundant PHB metabolic network. This study broadened the germplasm resources available for the bioconversion of sugarcane molasses, providing theoretical references for the valorization of high-concentration waste carbon sources.

Plastic particles in urban compost and their grain size distribution

Gathering information on plastic particles in composts and the processes they undergo is important in terms of potentially limiting their further entry into the environment, for example, in improving the fertilising properties of soils. Microplastics (MPs) were determined in composts produced from urban greenery. They are present in decreasing order: polyethylene terephthalate, polystyrene, polyethylene, and polypropylene. The determination of polymers and additives used to improve their properties was performed by pyrolysis and gas chromatography with mass spectrometric detection (Py-GC/MS). Additives and microplastics are most concentrated in composts in the 0.315-0.63 and 0.63-1.25 mm grain size class, together with the carbon contained in the compost dry matter. Additives form 0.11-0.13% of MPs in dry matter of compost. The average concentration of microplastics in the particle size class from 0.63 to 1.25 mm is 2434 ± 224 mg/kg; in the total sample of composts, it is 1368 ± 286 mg/kg of P-MPs. For composts with particle size <2.5 mm, a relationship between the C/N ratio and the plastic particle concentration was statistically significant. It documents a similar behaviour of lignocellulose and plastic particles during the degradation processes. A relationship between the concentration of polymer markers and additives in the compost dry matter and their concentrations in the leachate has been demonstrated. The leachability from compost is higher for additives than for chemical compounds originating from the decomposition of the main components of MPs. The suitability of the use of the compost for agricultural purposes was monitored by the germination index (GI) for watercress. The lowest value of the GI was determined in the particle size class from 0.63 to 1.25 mm. The leachability of polymer markers and additives alone cannot explain the low GI value in this grain size class. The GI value is also influenced by the leachability of chemical compounds characterised by the value of dissolved organic carbon (DOC) and water-leachable nitrogen (Nw). A statistically significant dependence between DOC/Nw and the germination index value was found.