Polyhydroxyalkanoates (PHAs) are biodegradable microbial polyesters that may reduce dependence on petroleum-derived plastics, but broader use remains constrained by production costs and tightly controlled cultivation. Thermophilic microorganisms have attracted increasing attention as promising PHA producers because they can be cultivated at elevated temperatures, reducing contamination risks and operational costs. In this study, a thermophilic Geobacillus sp. strain SL28 isolated from a Vietnamese hot spring was evaluated for its PHA-producing capability. Temperature, initial pH, carbon and nitrogen sources, C/N ratio, and cultivation time were examined. Intracellular inclusions were assessed by Sudan Black B and Nile Blue A staining and transmission electron microscopy, whereas the recovered polymer was characterized by FE-SEM, Fourier-transform infrared spectroscopy (FTIR), gas chromatography–mass spectrometry (GC–MS), 1H- and 13C-nuclear magnetic resonance (NMR) spectroscopy, capillary viscometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile testing. Under the optimized cultivation conditions identified by one-factor experimentation (50 °C, pH 7.0, sucrose, peptone, C/N 25:1, and 72 h), SL28 reached a dry cell weight of 2.215 ± 0.16 g/L and a PHA concentration of 1.383 ± 0.04 g/L, equivalent to 62.57 ± 2.82% of DCW. Structural characterization confirmed that the recovered polymer was poly(3-hydroxybutyrate) (PHB). The purified PHB also exhibited favorable thermal stability, a relatively high molecular weight, and satisfactory mechanical properties. These results demonstrate the potential of thermophilic Geobacillus sp. SL28 as a promising candidate for PHB production.
Microbial polyhydroxyalkanoates (PHAs) have drawn increasing attention as sustainable alternatives to conventional plastics. However, PHA market growth remains limited because of their elevated production costs. To address this challenge, this study investigated the valorization of food waste as a low-cost feedstock and the combination of yeast extract and nitrogen-rich waste as a co-nitrogen source for sustainable poly(3-hydroxybutyrate) (PHB) production by extremely halophilic archaeon Haloarcula sp. PLQ. Implementation of this strategy resulted in the production of 1.099 ± 0.205 g L-1 of biomass with a PHB concentration of 0.634 ± 0.0063 g L-1, corresponding to a gravimetric PHB content of approximately 60 ± 11.755% of its cell dry weight (CDW). However, the strain achieved a lower PHB content as determined by gas chromatography analysis (GC) of approximately 27.87 ± 0.067% of its CDW, which may be related to the co-extraction of non-PHB cellular components during gravimetric determination. Regarding the characterization of PHB film, the SEM-EDS analysis revealed a porous and heterogeneous surface morphology that was composed of approximately 56.38 wt% carbon and 35.27 wt% oxygen with minor amounts of sodium, chlorine, and magnesium. Regarding FTIR and Raman spectroscopy analyses, the functional groups were found to be similar to those of commercial PHB. The XRD pattern was also similar to that of pure PHB. TGA and DSC results confirmed that the film is a semi-crystalline polymer-based material, with a degree of crystallinity of 61.3%, as determined from the first DSC heating scan. The melting point and the maximum degradation temperature of PHB were found to be 157.3 and 293.35 °C, respectively. This present study demonstrates the potential of the haloarchaeal strain for converting carbon- and nitrogen-rich waste streams into biodegradable PHB, aligning with circular bioeconomy principles.
Manel Ben Abdallah, K. K. Sadasivuni, M. Cherif et al.· Journal of Environmental Man...· 0 citations
Polyhydroxyalkanoates (PHAs) are biodegradable biopolymers synthesized by bacteria as secondary metabolites under nutrient-limited conditions with excess carbon. However, PHA production is often constrained by the high cost of carbon substrates. The utilization of waste materials, such as waste frying oil, offers a cost-effective alternative. In this study, PHA was produced by Bacillus subtilis using waste frying oil as the carbon source. Cultivation was carried out in modified Mineral Salt Medium (MSM) supplemented with 2% waste frying oil and 0.1% yeast extract at 30°C and 150 rpm for 72 h. PHA was extracted using chloroform and precipitated with cold methanol. Sudan Black staining confirmed intracellular PHA accumulation. Fourier Transform Infrared Spectroscopy (FTIR) analysis identified characteristic PHA functional groups, including O–H, C–H, C=O, CH₃, C–O–C, and C–O. X-ray Diffraction (XRD) revealed a predominantly amorphous structure with low crystallinity and an average crystallite size of 42.87 nm. Scanning Electron Microscopy (SEM) showed a fibrous surface morphology. Thermal characterization by Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) indicated a melting temperature of 163.54°C and a degradation temperature of 311°C. These results demonstrate the potential of waste frying oil as an economical carbon source for PHA production by B. subtilis.
Siti Saleha, Fika Yunidar, Kartika Mz et al.· Journal of Carbazon· 0 citations
Background: Polyhdroxyalkanoate (PHA) is a biopolymer synthesized by some bacteria as a carbon and energy storage. It has similar characteristics to fossil-derived plastic. Hence, it is considered a replacement for nonbiodegradable plastic. However, the bacterial strain and culture conditions determine the biosynthesis and properties of PHA.
Objective: To determine the structure and properties of PHA produced by Rhodobacter sphaeroides ADZ101.
Methods: Fourier Transform Infrared spectroscopy (FTIR) was used to evaluate the functional groups of the PHA, thermal stability analysis was carried out using TGA, and molecular weight was determined with MALDI-TOF MS. Other structural analyses were performed using NMR and GC-MS.
Results: The results showed the presence of absorption bands related to the symmetrical CH3 group, carbonyl ester, bacterial intracellular protein amide, and the stretching vibration in the amorphous phase. Structural analysis revealed that the PHA contains short- and medium-length monomers in the order C5, C13, C14, to C18. The GCMS analysis showed that the PHA consisted of poly 3-hydroxybutyrate and poly 3-hydroxyvalerate with the presence of methyl esters of dodecanone, butyrate, hexadeconoic and heptadeconoic acids, and phenol 2,5 bis (1,1 dimethyl ethyl)-4-phenol. The estimated molecular weight of the polymer was 628.55 kDa. Thermal analysis revealed that the maximum PHA decomposition temperatures are 395 and 454°C, indicating two major decomposition reactions.
Conclusion: The PHA produced by R. sphaeroides ADZ101 exhibit enhanced temperature decomposition and has numerous potential industrial applications.
A. Idi, M. U. Maikudi, Hindatu Yusuf et al.· Baghdad Journal of Biochemis...· 0 citations
The increasing accumulation of plastic waste has intensified efforts to identify sustainable biodegradable alternatives. Polyhydroxyalkanoates (PHAs) are microbial polyesters with properties similar to conventional plastics; however, their commercial feasibility is limited by high production costs. This study investigated the use of oil palm waste, specifically palm kernel meal (PKM) and empty fruit bunch (EFB), as feedstocks for PHA production by Paraburkholderia sp. PFN29. Biomass pretreatment used sodium hydroxide (1-5% w/v) followed by hydrogen peroxide (3% v/v), and enzymatic hydrolysis with pectinase, xylanase, and cellulase. Reducing sugars were quantified using the dinitrosalicylic acid (DNS) method, and morphological changes were examined via scanning electron microscopy (SEM). Optimal saccharification with 3% (w/v) NaOH at 50°C for 48 h yielded 10.53±0.33 and 21.02±0.38 mg/mL reducing sugars from PKM and EFB, respectively. Glucose was the predominant sugar in both hydrolysates. PHA biosynthesis was assessed under various carbon- and nitrogen-supplementation conditions. The EFB hydrolysate at 100 ml supplemented with 0.1 g NH₄Cl produced the highest PHA concentration (1.12±0.02 g/L), PHA content (59.02%), and productivity (0.01 g/L/h), which was comparable to that of the mineral medium control. The PKM hydrolysate supported optimal PHA production without supplementation (PHA content, 39.02%). Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) analyses confirmed PHB-type PHA production. These findings indicate that palm oil residues, particularly EFB hydrolysates under optimized nitrogen conditions, are promising substrates for sustainable PHA production.
Sumintra Chaimongkol, T. Sriyapai, Pichapak Sriyapai· Current Applied Science and...· 0 citations
Lipases obtained from thermophilic microorganisms are attracting great interest in the industrial field due to their stability under high-temperature conditions and their wide range of industrial applications. In this study, thermophilic bacterial strains were isolated from water and mud samples collected from Erzurum Ilica Hot Springs (Turkey). An isolate producing a potent extracellular lipase was selected, named IO3, and identified by 16S rRNA sequencing. Sequencing analysis revealed that this isolate showed 99% similarity to Aeribacillus pallidus. The lipase enzyme purified from the isolate was obtained using two comparative strategies. The conventional multi-stage chromatographic approach, which includes ammonium sulfate precipitation, ion exchange chromatography, and gel filtration chromatography, provided 9.3-fold purification with a 3.18% recovery. However, the alternative Three-Phase Partitioning (TPP) system provided rapid, single-step recovery with a significantly higher yield of 38.79%, although the purification fold remained 0.65 under the tested conditions. The molecular weight of the purified A. pallidus IO3 lipase was determined to be approximately 33.88 kDa by SDS-PAGE. The enzyme showed optimum activity at pH 8.0 and 50 °C and maintained considerable thermal stability; the enzyme retained significant activity levels (45-69%) even at high temperatures such as 70 °C and 80 °C after an incubation period of 120 minutes. Among the tested metal ions, Fe2+, Fe³+, Cu2+, and Zn2+ enhanced enzyme activity, while the enzyme showed stability in the presence of Li+ and Cu2+ ions. Lipase activity also increased in the presence of surfactants, while chloroform enhanced enzyme activity by 22-338% depending on solvent concentration. The enzyme showed the highest activity toward p-nitrophenyl palmitate. The enzyme was completely inhibited by DTNB, IAA, and EDTA. In addition, the enzyme retained low activity in the presence of β-mercaptoethanol. The Km and Vmax values were calculated as 0.46 mM and 51.44 µmol·min-1·mg-1, respectively, using nonlinear regression analysis. Overall, these findings indicate that A. pallidus IO3 lipase is a thermostable and chemically tolerant enzyme with potential applicability in industrial biocatalysis and detergent-related processes.
Ikra Ozkan, A. Adiguzel· Preparative Biochemistry & B...· 0 citations
Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) is a biodegradable copolymer whose mechanical properties can be tuned by the 3-hydroxyhexanoate (3HHx) fraction. However, current industrial production largely relies on established hosts and plant oil-based feedstocks. Here, we developed Rhodobacter capsulatus SB1003 as a new PHBH-producing platform by focusing on the two key determinants of copolymer formation: polyhydroxyalkanoate (PHA) synthase substrate specificity and intracellular monomer supply. A PHA synthase with broad-substrate specificity was integrated into the native phaC locus to generate a heterologous phaC strain. All PHA production experiments were performed under anaerobic photoheterotrophic conditions in 8-mL screw-cap tubes containing 7.6 mL of medium and illuminated with continuous white light. During butyrate cultivation under these conditions, the engineered strain accumulated polymer up to 41.5% of cell dry weight and incorporated detectable 3HHx, whereas the wild type showed no 3HHx incorporation. To increase 3HHx-CoA availability from butyrate, we introduced C4-to-C6 precursor-supply modules involving β-ketothiolase (BktB)/β-ketoacyl-CoA reductase (PhaB) and crotonyl-CoA carboxylase/reductase (Ccr)/ethylmalonyl-CoA decarboxylase (Emd), but these modifications led to only marginal improvements in the 3HHx fraction. In contrast, supplying C6 or longer fatty acids under the same conditions markedly increased 3HHx incorporation; cultivation on hexanoate yielded PHBH containing 32.4 mol% 3HHx. Collectively, this study demonstrates PHBH biosynthesis in R. capsulatus and indicates that limited 3HHx-CoA supply rather than polymerization capacity is the primary bottleneck, providing a foundation for further pathway and host optimization toward flexible PHBH production from diverse substrates.
Kako Miura, Takayuki Shimizu, T. Hasunuma et al.· Journal of Bioscience and Bi...· 0 citations