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

Isolation and Characterization of Carbonosomes from Pseudomonas sp. phDV1 Grown Using Phenol as Carbon Source

The Pseudomonas sp. strain phDV1 was found to utilize monocyclic aromatic compounds as a sole carbon source and has a variety of potential applications in the bioremediation and biosynthesis of biodegradable plastics. It was possible to produce polyhydroxybutyrate when cultivated in the presence of monocyclic aromatic compounds as the sole carbon source. This study provides the small-scale optimization for phenol bioremediation and polyhydroxybutyrate production. The bacterium was cultivated in minimal medium supplemented with different concentrations of phenol. The formation and localization of the polyhydroxybutyrate granules (carbonosomes) in the cell were determined after 72 h of cultivation using Nile Red stain in combination with fluorescence microscopy. Analytical HPLC was also used to quantify the PHB content in the cells and to optimize the production. Finally, comparative proteomic analysis of isolated carbonosomes was used to characterize of their protein composition.

Controlled release of trifluralin herbicide using luminescent Vibrio-derived polyhydroxyalkanoate (PHA) microcapsules

The controlled release of herbicides using new and safe materials can mitigate environmental pollution. Polyhydroxyalkanoate (PHA) is a type of biopolymer that can be produced by various bacteria. It has properties that make it suitable for encapsulation and controlled release applications. A luminescent bacterium, Vibrio sp. VLC strain was used as the PHA producer in this study. Initially, the polymer was synthesized by the bacterium following optimization of the culture medium, resulting in an approximate yield of 25 %. Subsequently, the produced polymer was analyzed using TEM, FTIR, and H-NMR techniques. Microcapsules were produced using the emulsion method. FE-SEM imaging revealed spherical microcapsules with an average diameter of 0.5-2 μm. The herbicide loading content and encapsulation efficiency were determined to be 16.64 % and 66.56 %, respectively. The herbicidal effect of the microcapsules containing trifluralin was investigated using Amaranthus retroflexus and Setaria viridis plants, demonstrating a significant reduction in various parameters after application. Furthermore, the impact of encapsulated herbicide on soil microbial population was assessed, revealing a less negative effect compared to its free form. These findings suggest that the PHA from a luminescent vibrio holds promise as an eco-friendly, biodegradable, nontoxic material for the controlled release of herbicides.

Metabolic conversion of phenol to polyhydroxyalkanoate (PHA) for addressing dual environmental challenges: A review

A sustainable approach to microbial polyhydroxyalkanoate (PHA) production involves utilizing waste as a substrate, which can include toxic pollutants like phenol as a carbon feedstock. Phenol-contaminated effluents offer cost-effective and readily available resources for PHA production, while simultaneously addressing phenol contamination issues. Understanding the metabolic conversion of phenol to PHA is crucial to enhance its efficiency, especially considering phenol's toxicity to microbial cells and the substrate-dependent nature of microbial PHA production. In this review, the mechanisms of phenol biodegradation and PHA biosynthesis are first independently elucidated to comprehend the role of bacteria in these processes. Phenol can be metabolized aerobically via various pathways, including catechol meta-cleavage I and II, catechol ortho-cleavage, protocatechuate ortho-cleavage, and protocatechuate meta-cleavage, as well as anaerobically via 4-hydrozybenzoate and/or n-caproate formation. Meanwhile, PHA can be synthesized through the acetoacetyl-CoA (pathway I), de novo fatty acids synthesis (pathway II), β-oxidation (pathway III), and the tricarboxylic acid (TCA) cycle, with the induction of these pathways are highly dependent on the substrate. Given that the link between these two mechanisms was not comprehensively reported before, the second part of the review delve into understanding phenol conversion into PHA, specifically polyhydroxybutyrate (PHB). While phenol toxicity can inhibit bacterial performance, it can be alleviated through the utilization of microbial mixed culture (MMC), which offers a wider range of metabolic capabilities. Utilizing phenol as a carbon feedstock for PHB accumulation could offer a viable approach to boost PHA's commercialization while addressing the issue of phenol pollution.

Bacterial acquisition of host fatty acids has far-reaching implications on virulence

SUMMARYThe lipid homeostasis pathways of bacterial pathogens have been studied comprehensively for their biochemical functionality. However, new and refined technologies have supported the interrogation of bacterial lipid and fatty acid homeostasis mechanisms in more complex environments, such as mammalian host niches. In particular, emerging findings on the breadth and depth of host fatty acid uptake have demonstrated their importance beyond merely fatty acid utilization for membrane synthesis, as they can contribute to virulence factor regulation, pathogenesis, and group-based behaviors. Lipid homeostasis is also intertwined with other metabolic and physiological processes in the bacterial cells, which appear to be largely unique per species, but overarching themes can be derived. This review combines the latest biochemical and structural findings and places these in the context of bacterial pathogenesis, thereby shedding light on the far-reaching implications of lipid homeostasis on bacterial success.

Green alternatives to petroleum-based plastics: production of bioplastic from Pseudomonas neustonica strain NGB15 using waste carbon source

Polyhydroxyalkanoates have attracted great interest as a suitable alternative to petrochemical based plastics due to their outstanding properties such as biodegradability and biocompatibility. However, the biggest problem in the production of microbial polyhydroxyalkanoates is low cost-effectiveness. In this study, polyhydroxyalkanoate production was carried out using waste substrates with local isolates. Culture conditions were optimized to increase the polyhydroxyalkanoate production potential. The produced polyhydroxyalkanoate was characterized by FTIR analyses, and its metabolic pathway was determined by real-time PCR. According to the results, the best polyhydroxyalkanoate producer bacteria was characterized as Pseudomonas neustonica NGB15. The optimal culture conditions were detected as 30 g/L banana peel powder, 25 °C temperature, pH 8, and 4-day incubation time. Under the optimized conditions, 3.34 g/L PHA production was achieved. As a result of FTIR analyses, major peaks were obtained at 1723, 1277, 1261, 1097, 1054, and 993 cm-1. These peaks represent that the type of produced polyhydroxyalkanoate was poly-β-hydroxybutyrate. According to gene expression profile of NGB15, it was determined that Pseudomonas neustonica NGB15 produces PHA using the de novo fatty acid synthesis metabolic pathway. In conclusion, poly-β-hydroxybutyrate production by Pseudomonas neustonica NGB15 using a low-cost fermentation medium has been shown to be biotechnologically promising.

A sustainable synthesis of polyhydroxyalkanoate from stubble waste as a carbon source using Pseudomonas putida MTCC 2475

Polyhydroxyalkanoates (PHAs) are biodegradable polymers that can be produced from lignocellulosic biomass by microorganisms. Cheap and readily available raw material, such as corn stover waste, has the potential to lessen the cost of PHA synthesis. In this research study, corn stover is pretreated with NaOH under conditions optimized for high cellulose and low lignin with central composite design (CCD) followed by characterization using Fourier-transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). Design expert software performed further optimization of alkali pretreated corn stover for high total reducing sugar (TRS) enhancement using CCD using response surface methodology (RSM). The optimized condition by RSM produced a TRS yield of 707.19 mg/g. Fermentation using corn stover hydrolysate by Pseudomonas putida MTCC 2475 gave mcl-PHA detected through gas c hromatography - t andem m ass s pectrometry (GC-MS/MS) and characterization of the PHA film by differential scanning calorimetry (DSC), FTIR, and nuclear magnetic resonance (NMR). Thus, this research paper focuses on using agriculture (stubble) waste as an alternative feedstock for PHA production.

Exploring Bacillus amyloliquefaciens strain OM81 for the production of polyhydroxyalkanoate (PHA) bioplastic using olive mill wastewater

In this study, bacterial strains isolated from olive oil mill wastewater assigned to Bacillus (n = 4) and Klebsiella (n = 1) genera, were evaluated for their ability to accumulate intracellular PHA granules using Sudan Black staining. A maximum PHA production of 0.14 g/L (i.e., 30.2% wt./wt. in dry biomass) was observed in Bacillus amyloliquefaciens strain OM81 after 72 h of incubation in the presence of 2% glucose (synthetic medium). To reduce bioplastic production costs and recover a polluting product, olive mill wastewater was tested as a carbon source. In this context, the maximum growth (1.45 g/L) was observed in the presence of 50% olive mill wastewater. After extracting the biopolymers with chloroform, quantitative and qualitative analyses were conducted using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). FTIR showed an absorption band at 1730 cm-1 assigned to the elongation of the PHB carbonyl groups. This approach offers a dual benefit of reducing pollution and bioplastic production costs. The Bacillus amyloliquefaciens strain OM81 showed promising results for PHAs production, making it a potential candidate for further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03808-4.

Sustainable Polyhydroxyalkanoate Production from Food Waste via Bacillus mycoides ICRI89: Enhanced 3D Printing with Poly (Methyl Methacrylate) Blend

In view of implementing green technologies for bioplastic turning polices, novel durable feedstock for Bacillus mycoides ICRI89 used for efficient polyhydroxybutyrate (PHB) generation is proposed herein. First, two food waste (FW) pretreatment methods were compared, where the ultrasonication approach for 7 min was effective in easing the following enzymatic action. After treatment with a mixture of cellulase/amylases, an impressive 25.3 ± 0.22 g/L of glucose was liberated per 50 g of FW. Furthermore, a notable 2.11 ± 0.06 g/L PHB and 3.56 ± 0.11 g/L cell dry eight (CDW) over 120 h were generated, representing a productivity percentage of 59.3 wt% using 25% FW hydrolysate. The blend of polyhydroxybutyrate/poly (methyl methacrylate) (PHB/PMMA = 1:2) possessed the most satisfactory mechanical properties. For the first time, PHB was chemically crosslinked with PMMA using dicumyl peroxide (DCP), where a concentration of 0.3 wt% had a considerable effect on increasing the mechanical stability of the blend. FTIR analysis confirmed the molecular interaction between PHB and PMMA showing a modest expansion of the C=O stretching vibration at 1725 cm-1. The DCP-PHB/PMMA blend had significant thermal stability and biodegradation profiles comparable to those of the main constituent polymers. More importantly, a 3-Dimetional (3D) filament was successfully extruded with a diameter of 1.75 mm, where no blockages or air bubbles were noticed via SEM. A new PHB/PMMA "key of life" 3D model has been printed with a filling percentage of 60% and a short printing time of 19.2 min. To conclude, high-performance polymeric 3D models have been fabricated to meet the pressing demands for future applications of sustainable polymers.

Production of Polyhydroxybutyrate by Genetically Modified Pseudomonas sp. phDV1: A Comparative Study of Utilizing Wine Industry Waste as a Carbon Source

Pseudomonas sp. phDV1 is a polyhydroxyalkanoate (PHA) producer. The presence of the endogenous PHA depolymerase (phaZ) responsible for the degradation of the intracellular PHA is one of the main shortages in the bacterial production of PHA. Further, the production of PHA can be affected by the regulatory protein phaR, which is important in accumulating different PHA-associated proteins. PHA depolymerase phaZ and phaR knockout mutants of Pseudomonas sp. phDV1 were successfully constructed. We investigate the PHA production from 4.25 mM phenol and grape pomace of the mutants and the wild type. The production was screened by fluorescence microscopy, and the PHA production was quantified by HPLC chromatography. The PHA is composed of Polydroxybutyrate (PHB), as confirmed by ¹H-nuclear magnetic resonance analysis. The wildtype strain produces approximately 280 μg PHB after 48 h in grape pomace, while the phaZ knockout mutant produces 310 μg PHB after 72 h in the presence of phenol per gram of cells, respectively. The ability of the phaZ mutant to synthesize high levels of PHB in the presence of monocyclic aromatic compounds may open the possibility of reducing the costs of industrial PHB production.

Environmental impacts of microplastic and role of plastisphere microbes in the biodegradation and upcycling of microplastic

Increasing usage of plastic has led to the deposition of plastic in the environment which later become microplastic, a pollutant of global concern. These polymeric particles affect the ecosystem bestowing toxicity and impede the biogeochemical cycles. Besides, microplastic particles have been known for their role in aggravating the effect of various other environmental pollutants including organic pollutants and heavy metals. These microplastic surfaces are often colonized by the microbial communities also known as "plastisphere microbes" forming biofilms. These microbes include cyanobacteria like Nostoc, Scytonema, etc., and diatoms like Navicula, Cyclotella, etc. Which become the primary colonizer. In addition to the autotrophic microbes, Gammaproteobacteria and Alphaproteobacteria dominate the plastisphere microbial community. These biofilm-forming microbes can efficiently degrade the microplastic in the environment by secreting various catabolic enzymes such as lipase, esterase, hydroxylase, etc. Besides, these microbes have shown great potential for the bioconversion of microplastic to polyhydroxyalkanoates (PHA), an energy efficient and sustainable alternative to the petroleum based plastics. Thus, these microbes can be used for the creation of a circular economy using waste to wealth strategy. This review provides a deeper insight into the distribution, transportation, transformation, and biodegradation of microplastic in the ecosystem. The formation of plastisphere by the biofilm-forming microbes has been described in the article. In addition, the microbial metabolic pathways and genetic regulations involved in the biodegradation have been discussed in detail. The article suggests the microbial bioremediation and upcycling of microplastic along with various other strategies for effectively mitigate the microplastic pollution.

Commercialization potential of agro-based polyhydroxyalkanoates biorefinery: A technical perspective on advances and critical barriers

The exponential increase in the use and careless discard of synthetic plastics has created an alarming concern over the environmental health due to the detrimental effects of petroleum based synthetic polymeric compounds. Piling up of these plastic commodities on various ecological niches and entry of their fragmented parts into soil and water has clearly affected the quality of these ecosystems in the past few decades. Among the many constructive strategies developed to tackle this global issue, use of biopolymers like polyhydroxyalkanoates as sustainable alternatives for synthetic plastics has gained momentum. Despite their excellent material properties and significant biodegradability, polyhydroxyalkanoates still fails to compete with their synthetic counterparts majorly due to the high cost associated with their production and purification thereby limiting their commercialization. Usage of renewable feedstocks as substrates for polyhydroxyalkanoates production has been the thrust area of research to attain the sustainability tag. This review work attempts to provide insights about the recent developments in the production of polyhydroxyalkanoates using renewable feedstock along with various pretreatment methods used for substrate preparation for polyhydroxyalkanoates production. Further, the application of blends based on polyhydroxyalkanoates, and the challenges associated with the waste valorization based polyhydroxyalkanoates production strategy is elaborated in this review work.

Characterization of a New Pseudomonas Putida Strain Ch2, a Degrader of Toxic Anthropogenic Compounds Epsilon-Caprolactam and Glyphosate

In this work, a new Ch2 strain was isolated from soils polluted by agrochemical production wastes. This strain has a unique ability to utilize toxic synthetic compounds such as epsilon-caprolactam (CAP) as a sole carbon and energy source and the herbicide glyphosate (GP) as a sole source of phosphorus. Analysis of the nucleotide sequence of the 16S rRNA gene of Ch2 revealed that the strain belongs to the species Pseudomonas putida. This strain grew in the mineral medium containing CAP in a concentration range of 0.5 to 5.0 g/L and utilized 6-aminohexanoic acid and adipic acid, which are the intermediate products of CAP catabolism. The ability of strain Ch2 to degrade CAP is determined by a conjugative megaplasmid that is 550 kb in size. When strain Ch2 is cultured in a mineral medium containing GP (500 mg/L), more intensive utilization of the herbicide occurs in the phase of active growth. In the phase of declining growth, there is an accumulation of aminomethylphosphonic acid, which indicates that the C-N bond is the first site cleaved during GP degradation (glyphosate oxidoreductase pathway). Culture growth in the presence of GP during the early step of its degradation is accompanied by unique substrate-dependent changes in the cytoplasm, including the formation of vesicles of cytoplasmic membrane consisting of specific electron-dense content. There is a debate about whether these membrane formations are analogous to metabolosomes, where the primary degradation of the herbicide can take place. The studied strain is notable for its ability to produce polyhydroxyalkanoates (PHAs) when grown in mineral medium containing GP. At the beginning of the stationary growth phase, it was shown that, the amount and size of PHA inclusions in the cells drastically increased; they filled almost the entire volume of cell cytoplasm. The obtained results show that the strain P. putida Ch2 can be successfully used for the PHAs’ production. Moreover, the ability of P. putida Ch2 to degrade CAP and GP determines the prospects of its application for the biological cleanup of CAP production wastes and in situ bioremediation of soil polluted with GP.

Genotypic and Phenotypic Detection of Polyhydroxyalkanoate Production in Bacterial Isolates from Food

Polyhydroxyalkanoates (PHAs) are widely used in medical and potentially in other applications due to their biocompatibility and biodegradability. Understanding PHA biosynthetic pathways may lead to the detection of appropriate conditions (substrates) for producing a particular PHA type by a specific microbial strain. The aim of this study was to establish a method enabling potentially interesting PHA bacterial producers to be found. In the study, all four classes of PHA synthases and other genes involved in PHA formation (fabG, phaA, phaB, phaG, and phaJ) were detected by PCR in 64 bacterial collection strains and food isolates. Acinetobacter, Bacillus, Cupriavidus, Escherichia, Klebsiella, Lelliottia, Lysinibacillus, Mammaliicoccus, Oceanobacillus, Pantoea, Peribacillus, Priestia, Pseudomonas, Rahnella, Staphylococcus, and Stenotrophomonas genera were found among these strains. Fructose, glucose, sunflower oil, and propionic acid were utilized as carbon sources and PHA production was detected by Sudan black staining, Nile blue staining, and FTIR methods. The class I synthase and phaA genes were the most frequently found, indicating the strains' ability to synthesize PHA from carbohydrates. Among the tested bacterial strains, the Pseudomonas genus was identified as able to utilize all tested carbon sources. The Pseudomonas extremorientalis strain was determined as a prospect for biotechnology applications.

Characterization of P(3HB) from untreated raw palm oil mill effluent using Azotobacter vinelandii ΔAvin_16040 lacking S-layer protein

The production of poly(3-hydroxybutyrate) [P(3HB)] from untreated raw palm oil mill effluent (urPOME), the first wastewater discharge from crude palm oil extraction, is discussed. The mutant strain Azotobacter vinelandii ΔAvin_16040, which lacks the S-layer protein but has a better P(3HB) synthesis capability than the wild type strain ATCC 12,837, was chosen for this study. UrPOME substrate, with high biological oxygen demand (BOD), chemical oxygen demand (COD) and suspended solids, was used without pre-treatment. DSMZ-Azotobacter medium which was devoid of laboratory sugar(s) was used as the basal medium (BaM). Initially, Azotobacter vinelandii ΔAvin_16040 generated 325.5, 1496.3, and 1465.7 mg L^-1 of P(3HB) from BaM with 20% urPOME, 2BaM with 20% urPOME and 20 g L^-1 sucrose, and 2BaM with 20% urPOME and 2 mL L^-1 glycerol, respectively. P(3HB) generation was enhanced by nearly tenfold using statistical optimization, resulting in 13.9 g L^-1. Moreover, the optimization reduced the compositions of mineral salts and sugar in the medium by 48 and 97%, respectively. The urPOME-based P(3HB) product developed a yellow coloration most possibly attributed to the aromatic phenolics content in urPOME. Despite the fact that both were synthesised by ΔAvin_16040, thin films of urPOME-based P(3HB) had superior crystallinity and tensile strength than P(3HB) produced only on sucrose. When treated with 10 and 50 kGy of electron beam irradiation, these P(3HB) scissioned to half and one-tenth of their original molecular weights, respectively, and these cleavaged products could serve as useful base units for specific polymer structure construction.

Techno-economic analysis of food waste valorization for integrated production of polyhydroxyalkanoates and biofuels

This study focused on the techno-economic analysis of integrated polyhydroxyalkanoates (PHAs) and biofuels such as biohydrogen, bioethanol, and 2,3-butanediol production from food waste (FW). Based on previous literature studies, the integrated process was developed. The process plan produced 2.01 MT of PHAs, 0.29 MT of biohydrogen, 4.79 MT of bioethanol, and 6.79 MT of 2,3-butanediol per day, from 50 MT of FW. The process plan has a positive net present value of 4.47 M$, a 13.68% return on investment, a payback period of 7.31 yr, and an internal rate of return of 11.95%. Sensitivity analysis was used to examine the economic feasibility. The actual minimum selling price (MSP) of PHAs was 4.83 $/kg, and the lowest achievable MSP with 30% solid loading is 2.41 $/kg. The solid loading in the hydrolysis stage and the price of byproducts have a major impact on the economic factors and MSP of PHAs.

Contribution of Fermentation Technology to Building Blocks for Renewable Plastics

Large-scale worldwide production of plastics requires the use of large quantities of fossil fuels, leading to a negative impact on the environment. If the production of plastic continues to increase at the current rate, the industry will account for one fifth of global oil use by 2050. Bioplastics currently represent less than one percent of total plastic produced, but they are expected to increase in the coming years, due to rising demand. The usage of bioplastics would allow the dependence on fossil fuels to be reduced and could represent an opportunity to add some interesting functionalities to the materials. Moreover, the plastics derived from bio-based resources are more carbon-neutral and their manufacture generates a lower amount of greenhouse gasses. The substitution of conventional plastic with renewable plastic will therefore promote a more sustainable economy, society, and environment. Consequently, more and more studies have been focusing on the production of interesting bio-based building blocks for bioplastics. However, a coherent review of the contribution of fermentation technology to a more sustainable plastic production is yet to be carried out. Here, we present the recent advancement in bioplastic production and describe the possible integration of bio-based monomers as renewable precursors. Representative examples of both published and commercial fermentation processes are discussed.

Optimization of Propagation Medium for Enhanced Polyhydroxyalkanoate Production by Pseudomonas oleovorans

Polyhydroxyalkanoates (PHAs) represent a promising alternative to commercially used petroleum-based plastics. Pseudomonas oleovorans is a natural producer of medium-chain-length PHA (mcl-PHA) under cultivation conditions with nitrogen limitation and carbon excess. Two-step cultivation appears to be an efficient but more expensive method of PHA production. Therefore, the aim of this work was to prepare a minimal synthetic medium for maximum biomass yield and to optimize selected independent variables by response surface methodology (RSM). The highest biomass yield (1.71 ± 0.04 g/L) was achieved in the optimized medium containing 8.4 g/L glucose, 5.7 g/L sodium ammonium phosphate and 35.4 mM phosphate buffer. Under these conditions, both carbon and nitrogen sources were completely consumed after 48 h of the cultivation and the biomass yield was 1.7-fold higher than in the conventional medium recommended by the literature. This approach demonstrates the possibility of using two-stage PHA cultivation to obtain the maximum amount of biomass and PHA.