Psychrotrophic Pseudomonas mandelii CBS-1 produces high levels of poly-β-hydroxybutyrate

Characterization of Poly(3-hydroxybutyrate) (P3HB) from Alternative, Scalable (Waste) Feedstocks

Bioplastics hold significant promise in replacing conventional plastic materials, linked to various serious issues such as fossil resource consumption, microplastic formation, non-degradability, and limited end-of-life options. Among bioplastics, polyhydroxyalkanoates (PHA) emerge as an intriguing class, with poly(3-hydroxybutyrate) (P3HB) being the most utilized. The extensive application of P3HB encounters a challenge due to its high production costs, prompting the investigation of sustainable alternatives, including the utilization of waste and new production routes involving CO2 and CH4. This study provides a valuable comparison of two P3HBs synthesized through distinct routes: one via cyanobacteria (Synechocystis sp. PCC 6714) for photoautotrophic production and the other via methanotrophic bacteria (Methylocystis sp. GB 25) for chemoautotrophic growth. This research evaluates the thermal and mechanical properties, including the aging effect over 21 days, demonstrating that both P3HBs are comparable, exhibiting physical properties similar to standard P3HBs. The results highlight the promising potential of P3HBs obtained through alternative routes as biomaterials, thereby contributing to the transition toward more sustainable alternatives to fossil polymers.

Valorization of food waste derived anaerobic digestate into polyhydroxyalkanoate (PHA) using Thauera mechernichensis TL1

Polyhydroxyalkanoate (PHA) is a biopolymer that can be used as a bioplastic, offering a green alternative to petroleum-based plastics. In this study, we investigated PHA production using Thauera mechernichensis TL1. The optimal molar C/N ratio was determined to be 20 from among the ratios of 4, 20, 40, 80, and 200 and in the absence of nitrogen. Food waste anaerobic digestate, mainly comprised of acetate and propionate, was used as the carbon source for PHA production by T. mechernichensis TL1, resulting in a maximum PHA content of 23.98 ± 0.52 wt% (0.52 ± 0.02 g/L PHA) with a PHA productivity of 0.043 g/L-h PHA. In addition, when using acetate and propionate, T. mechernichensis TL1 produced PHA with a maximum PHA content of 57.43 ± 2.84 wt% (2.04 ± 0.11 g/L PHA) and 50.94 ± 1.61 wt% (2.62 ± 0.16 g/L PHA), with a PHA productivity of 0.092 g/L-h PHA and 0.070 g/L-h PHA, respectively. Proton nuclear magnetic resonance spectroscopy (1H NMR) confirmed polyhydroxybutyrate (PHB) production using acetate as a carbon source, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) production using propionate or food waste anaerobic digestate as the carbon source. The whole-genome analysis of T. mechernichensis TL1 confirmed the existence of a PHA biosynthesis pathway, with the presence of phaA, phaB, phaC (Class I and Class II), and phaJ genes. This study was the first to demonstrate Thauera sp.'s ability to produce PHA from food waste anaerobic digestate, rendering it as a promising candidate for PHA-producing bacteria for the valorization of food waste.

In-silico analysis of a halophilic bacterial isolate-Bacillus pseudomycoides SAS-B1 and its polyhydroxybutyrate production through fed-batch approach under differential salt conditions

Polyhydroxybutyrate (PHB) is a natural biopolymer and a viable substitute for petroleum-derived polymers that possess immense potential for diverse applications. In the present study, PHB was produced by a halophilic bacteria identified as Bacillus pseudomycoides SAS-B1 by 16S rRNA gene sequencing. The bacterial genome was evaluated through complete genome sequencing, which elucidated a 5,338,308 bp genome with 34.88 % of G + C content and 5660 genes. Other genome attributes were analyzed such as functional profiling, gene ontology, and metabolic pathways. Genes involved in PHB biochemical pathway were identified such as phaA, phaB, and phaC. Furthermore, sodium-dependent transporters and other ATP-binding genes were identified in the genome that may be involved in sodium uptake during saline conditions. The PHB production by B. pseudomycoides SAS-B1 was examined under differential salt conditions. The PHB yield was increased from 3.14 ± 0.02 g/L to 6.12 ± 0.04 g/L when salinity was increased upto 20 g/L with intermittent feeding of glucose and corn steep liquor. FTIR, NMR, and GC-MS studies elucidated the presence of desired functional groups, molecular structure, and monomeric compositions of PHB respectively. Further, TGA revealed the thermal stability of the recovered PHB upto (220-230) °C and has a crystallinity index of upto 33 ± 0.5 % as confirmed by XRD analysis.

Cupriavidus necator-Produced Polyhydroxybutyrate/Eudragit FS Hybrid Nanoparticles Mitigates Ulcerative Colitis via Colon-Targeted Delivery of Cyclosporine A

Polyhydroxybutyrate (PHB) has emerged as a novel material for replacing various plastics used in the medical field. However, its application as a drug-delivery carrier for colitis-targeted delivery has not been explored. In this study, we used biosynthesized PHB combined with Eudragit FS (EFS) and cyclosporine A (CSA) to develop pH-responsive controlled CSA-releasing nanoparticles (CSA-PENPs) for colitis-targeted drug delivery and demonstrated its enhanced therapeutic efficacy in a dextran sulfate sodium (DSS)-induced murine colitis model. PHB was successfully biosynthesized in the bacterium Cupriavidus necator, as demonstrated by ¹H-NMR and FT-IR analyses. CSA-PENPs were fabricated via the oil-in-water emulsion solvent evaporation method. Owing to the potent pH-responsive and sustained drug release properties provided by PHB and EFS, CSA-PENPs could deliver a sufficient amount of CSA to inflamed tissues in the distal colon; in contrast, CSA-loaded EFS nanoparticles displayed premature burst release before reaching the target site. Due to enhanced CSA delivery to colitis tissues, CSA-PENPs exhibited potent anti-inflammatory effects in the DSS-induced murine colitis model. Overall, CSA-PENPs could be a promising drug-delivery system for treating ulcerative colitis.

The Hyperproduction of Polyhydroxybutyrate Using Bacillus mycoides ICRI89 through Enzymatic Hydrolysis of Affordable Cardboard

Bioplastics are contemplated as remarkable substitutes for conventional plastics to accommodate green technological advancements. However, their industrial production has not been fully implemented owing to the cost of carbon resources. From another perspective, valorizing different paper mill wastes has become a prominent research topic. These materials may serve as an affording sustainable feedstock for bioplastic production. Adjustment of cardboard waste hydrolysate as suitable fermentation media for production of bacterial polyhydroxyalkanoates (PHAs) has been investigated. Cardboard samples were defibered and dried before enzymatic hydrolysis. The enzymatic degradation of commercial cellulase was monitored over 15 days. Interestingly, 18.2 ± 0.2 g/L glucose yield was obtained from 50 g cardboard samples using a 1.5% (v/v) enzyme concentration. The samples exhibited maximum weight loss values of 69-73%. Meanwhile, five soil samples were collected from local sites in Lodz, Poland. A total of 31 bacterial isolates were screened and cultured on Nile blue plates. Analysis of the 16S rRNA gene sequence of the most potent producer revealed 100% similarity to Bacillus mycoides. Cardboard hydrolysates whole medium, modified MSM with cardboard hydrolysate and nitrogen depleted MSM with cardboard hydrolysate were utilized for PHA production, followed by PHA productivity and cell dry weight (CDW) estimation compared to glucose as a standard carbon source. An impressive PHA accumulation of 56% CDW was attained when the waste hydrolysate was used as a carbon source. FTIR and NMR analysis of the isolated PHA indicated that functional groups of the polymer were related to PHB (polyhydroxybutyrate). Thermal analysis demonstrates that PHB and PHB-CB (PHB produced from cardboard hydrolysate) have degradation temperatures of 380 and 369 °C, respectively, which reflect the high thermal stability and heat resistance compared to the same properties for a standard polymer. This is the first demonstration of full saccharification of corrugated cardboard paper waste for high-level production of PHA. In addition, the attained PHB productivity is one of the highest levels achieved from a real lignocellulosic waste.

Polyhydroxyalkanoate (PHA) Production in Pseudomonas sp. phDV1 Strain Grown on Phenol as Carbon Sources

Pseudomonas strains have a variety of potential uses in bioremediation and biosynthesis of biodegradable plastics. Pseudomonas sp. strain phDV1, a Gram-negative phenol degrading bacterium, has been found to utilize monocyclic aromatic compounds as sole carbon source via the meta-cleavage pathway. The degradation of aromatic compounds comprises an important step in the removal of pollutants. The present study aimed to investigate the ability of the Pseudomonas sp. strain phDV1 to produce polyhydroxyalkanoates (PHAs) and examining the effect of phenol concentration on PHA production. The bacterium was cultivated in minimal medium supplemented with different concentrations of phenol ranging from 200-600 mg/L. The activity of the PHA synthase, the key enzyme which produces PHA, was monitored spectroscopically in cells extracts. Furthermore, the PHA synthase was identified by mass spectrometry in cell extracts analyzed by SDS-PAGE. Transmission electron micrographs revealed abundant electron-transparent intracellular granules. The isolated biopolymer was confirmed to be polyhydroxybutyrate (PHB) by FTIR, NMR and MALDI-TOF/TOF analyses. The ability of strain Pseudomonas sp. phDV1 to remove phenol and to produce PHB makes the strain a promising biocatalyst in bioremediation and biosynthesis of biodegradable plastics.

Fructose-Based Production of Short-Chain-Length and Medium-Chain-Length Polyhydroxyalkanoate Copolymer by Arctic Pseudomonas sp. B14-6

Arctic bacteria employ various mechanisms to survive harsh conditions, one of which is to accumulate carbon and energy inside the cell in the form of polyhydroxyalkanoate (PHA). Whole-genome sequencing of a new Arctic soil bacterium Pseudomonas sp. B14-6 revealed two PHA-production-related gene clusters containing four PHA synthase genes (phaC). Pseudomonas sp. B14-6 produced poly(6% 3-hydroxybutyrate-co-94% 3-hydroxyalkanoate) from various carbon sources, containing short-chain-length PHA (scl-PHA) and medium-chain-length PHA (mcl-PHA) composed of various monomers analyzed by GC-MS, such as 3-hydroxybutyrate, 3-hydroxyhexanoate, 3-hydroxyoctanoate, 3-hydroxydecanoate, 3-hydroxydodecenoic acid, 3-hydroxydodecanoic acid, and 3-hydroxytetradecanoic acid. By optimizing the PHA production media, we achieved 34.6% PHA content using 5% fructose, and 23.7% PHA content using 5% fructose syrup. Differential scanning calorimetry of the scl-co-mcl PHA determined a glass transition temperature (T_g) of 15.3 °C, melting temperature of 112.8 °C, crystallization temperature of 86.8 °C, and 3.82% crystallinity. In addition, gel permeation chromatography revealed a number average molecular weight of 3.6 × 10⁴, weight average molecular weight of 9.1 × 10⁴, and polydispersity index value of 2.5. Overall, the novel Pseudomonas sp. B14-6 produced a polymer with high medium-chain-length content, low T_g, and low crystallinity, indicating its potential use in medical applications.

Psychrozymes as novel tools to biodegrade p-xylene and potential use for contaminated groundwater in the cold climate

Sites contaminated by petroleum hydrocarbons in cold-climate regions have recently received significant attention due to their sensitive ecosystem and human health impacts. Two cold-adapted pseudomonas strains were isolated from contaminated groundwater and soil. As xylene monooxygenase from Pseudomonas synxantha S2TR-26 and catechol 2,3-dioxygenase from Pseudomonas mandelii S2TR-08, have a matching end product, they acted in symphony to degrade p-xylene. Their unique thermodynamic and kinetic behavior permits them to achieve rapid degradation of p-xylene at low temperatures (<15 °C). The results showed that the sequential action led to the conversion of 200 mg/l of p-xylene within 72 h and complete degradation after 120 h. The cocktail of these enzymes with a ratio of 1:1.5 (xylene monooxygenase: catechol 2, 3-dioxygenase) confirmed the complete degradation of p-xylene within 48 h at 15 °C. This approach will allow efficient biodegradation of p-xylene to minimize the bioremediation duration in cold-climate regions.

Efficient polyhydroxybutyrate production from Bacillus juice substrate thuringiensis using sugarcane

The present study focused on the screening and optimization of biopolymer polyhydroxybutyrate (PHB) production by Bacillus spp. using cost-effective substrates. Among 602 local Bacillus isolates, Bacillus thuringiensis B417-5 produced the highest amount of PHB (2.278 g/L, 60.07% of dry cell weight, DCW). 1H NMR and FTIR analyses of the extracted polymer revealed the characteristic peaks of PHB. The optimization results showed that the highest PHB accumulation (2.768 g/L, 72.08% of DCW) was achieved when culturing B. thuringiensis B417-5 in a nitrogen-deficient medium containing 1% total sugar from sugarcane juice and 0.5% yeast extract, with a pH of 7.0 and an incubation temperature of 37 °C for 48 h. B. thuringiensis B417-5 can thus be considered a good candidate for large-scale production of PHB. We are reporting for the first time that sugarcane juice is a promising carbon source for economical PHB production by B. thuringiensis.

Bacterial polyhydroxyalkanoates: Still fabulous?

Bacterial polyhydroxyalkanoates (PHA) are polyesters accumulated as carbon and energy storage materials under limited growth conditions in the presence of excess carbon sources. They have been developed as biomaterials with unique properties for the past many years being considered as a potential substitute for conventional non-degradable plastics. Due to the increasing concern towards global climate change, depleting petroleum resource and problems with an utilization of a growing number of synthetic plastics, PHAs have gained much more attention from industry and research. These environmentally friendly microbial polymers have great potential in biomedical, agricultural, and industrial applications. However, their production on a large scale is still limited. This paper describes the backgrounds of PHAs and discussed the current state of knowledge on the polyhydroxyalkanoates. Ability of bacteria to convert different carbon sources to PHAs, the opportunities and challenges of their introduction to global market as valuable renewable products have been also discussed.

Identification of a new polyhydroxyalkanoate (PHA) producer Aquitalea sp. USM4 (JCM 19919) and characterization of its PHA synthase

Aquitalea sp. USM4 (JCM 19919) was isolated from a freshwater sample at Lata Iskandar Waterfall in Perak, Malaysia. It is a rod-shaped, gram-negative bacterium with high sequence identity (99%) to Aquitalea magnusonii based on 16S rRNA gene analysis. Aquitalea sp. USM4 also possessed a PHA synthase gene (phaC), which had amino acid sequence identity of 77-78% to the PHA synthase of Chromobacterium violaceum ATCC12472 and Pseudogulbenkiania sp. NH8B. PHA biosynthesis results showed that wild-type Aquitalea sp. USM4 was able to accumulate up to 1.5 g/L of poly(3-hydroxybutyrate), [P(3HB)]. The heterologous expression of the PHA synthase gene of Aquitalea sp. USM4 (phaC_Aq) in Cupriavidus necator PHB^-4 had resulted in PHA accumulation up to 3.2 g/L of P(3HB). It was further confirmed by ¹H nuclear magnetic resonance (NMR) analysis that Aquitalea sp. USM4 and C. necator PHB^-4 transformant were able to produce PHA containing 3-hydroxyvalerate (3HV), 4-hydroxybutyrate (4HB) and 3-hydroxy-4-methylvalerate (3H4MV) monomers from suitable precursor substrates. Interestingly, relatively high PHA synthase activity of 863 U/g and 1402 U/g were determined in wild-type Aquitalea sp. USM4 and C. necator PHB^-4 transformant respectively. This is the first report on the member of genus Aquitalea as a new PHA producer as well as in vitro and in vivo characterization of a novel PHA synthase from Aquitalea sp. USM4.

Genome Sequence of Pseudomonas mandelii PD30

The genome sequence of Pseudomonas mandelii PD30 is reported in this announcement. The genes for the reduction of nitrate to dinitrogen were identified in the genome assembly and subsequently used in gene expression research.