Microorganisms produce diverse polymers for various purposes such as storing genetic information, energy, and reducing power, and serving as structural materials and scaffolds. Among these polymers, ...polyhydroxyalkanoates (PHAs) are microbial polyesters synthesized and accumulated intracellularly as a storage material of carbon, energy, and reducing power under unfavorable growth conditions in the presence of excess carbon source. PHAs have attracted considerable attention for their wide range of applications in industrial and medical fields. Since the first discovery of PHA accumulating bacteria about 100 years ago, remarkable advances have been made in the understanding of PHA biosynthesis and metabolic engineering of microorganisms toward developing efficient PHA producers. Recently, nonnatural polyesters have also been synthesized by metabolically engineered microorganisms, which opened a new avenue toward sustainable production of more diverse plastics. Herein, the current state of PHAs and nonnatural polyesters is reviewed, covering mechanisms of microbial polyester biosynthesis, metabolic pathways, and enzymes involved in biosynthesis of short‐chain‐length PHAs, medium‐chain‐length PHAs, and nonnatural polyesters, especially 2‐hydroxyacid‐containing polyesters, metabolic engineering strategies to produce novel polymers and enhance production capabilities and fermentation, and downstream processing strategies for cost‐effective production of these microbial polyesters. In addition, the applications of PHAs and prospects are discussed.
Polyhydroxyalkanoates (PHAs) are biodegradable and bio‐based polymers that can substitute petroleum‐based plastics currently in use. A comprehensive overview of the mechanisms and metabolism of PHA biosynthesis, and strategies for strain development, fermentation, and downstream processing toward the cost‐effective production of natural and nonnatural polyesters having diverse material properties is provided. Additionally, applications of PHAs and future prospects are discussed.
Plastics, including poly(ethylene terephthalate) (PET), possess many desirable characteristics and thus are widely used in daily life. However, non-biodegradability, once thought to be an advantage ...offered by plastics, is causing major environmental problem. Recently, a PET-degrading bacterium, Ideonella sakaiensis, was identified and suggested for possible use in degradation and/or recycling of PET. However, the molecular mechanism of PET degradation is not known. Here we report the crystal structure of I. sakaiensis PETase (IsPETase) at 1.5 Å resolution. IsPETase has a Ser-His-Asp catalytic triad at its active site and contains an optimal substrate binding site to accommodate four monohydroxyethyl terephthalate (MHET) moieties of PET. Based on structural and site-directed mutagenesis experiments, the detailed process of PET degradation into MHET, terephthalic acid, and ethylene glycol is suggested. Moreover, other PETase candidates potentially having high PET-degrading activities are suggested based on phylogenetic tree analysis of 69 PETase-like proteins.
Widespread utilization of polyethylene terephthalate (PET) has caused a variety of environmental and health problems; thus, the enzymatic degradation of PET can be a promising solution. Although ...PETase from Ideonalla sakaiensis (IsPETase) has been reported to have the highest PET degradation activity under mild conditions of all PET-degrading enzymes reported to date, its low thermal stability limits its ability for efficient and practical enzymatic degradation of PET. Using the structural information on IsPETase, we developed a rational protein engineering strategy using several IsPETase variants that were screened for high thermal stability to improve PET degradation activity. In particular, the IsPETaseS121E/D186H/R280A variant, which was designed to have a stabilized β6-β7 connecting loop and extended subsite IIc, had a T m value that was increased by 8.81 °C and PET degradation activity was enhanced by 14-fold at 40 °C in comparison with IsPETaseWT. The designed structural modifications were further verified through structure determination of the variants, and high thermal stability was further confirmed by a heat-inactivation experiment. The proposed strategy and developed variants represent an important advancement for achieving the complete biodegradation of PET under mild conditions.
Colorectal cancer (CRC) is the most common type cancers in the world. CRC occurs sporadically in the majority of cases, indicating the predominant cause of the disease are environmental factors. ...Diet-induced changes in gut-microbiome are recently supposed to contribute on epidemics of CRC. This study was aimed to investigate the association of metagenomics and metabolomics in gut extracellular vesicles (EVs) of CRC and healthy subjects. A total of 40 healthy volunteers and 32 patients with CRC were enrolled in this study. Metagenomic profiling by sequencing 16 S rDNA was performed for assessing microbial codiversity. We explored the small molecule metabolites using gas chromatography-time-of-flight mass spectrometry. In total, stool EVs were prepared from 40 healthy volunteers and 32 patients with CRC. Metagenomic profiling demonstrated that bacterial phyla, particularly of Firmicutes and Proteobacteria, were significantly altered in patients with colorectal cancer. Through metabolomics profiling, we determined seven amino acids, four carboxylic acids, and four fatty acids; including short-chain to long chain fatty acids that altered in the disease group. Binary logistic regression was further tested to evaluate the diagnostic performance. In summary, the present findings suggest that gut flora dysbiosis may result in alternation of amino acid metabolism, which may be correlated with the pathogenesis of CRC.
Excess fructose consumption contributes to development obesity, metabolic syndrome, and nonalcoholic fatty liver disease (NAFLD). Uric acid (UA), a metabolite of fructose metabolism, may have a ...direct role in development of NAFLD, with unclear mechanism. This study aimed to evaluate role of fructose and UA in NAFLD and explore mechanisms of allopurinol (Allo, a UA lowering medication) on NAFLD in Otsuka Long-Evans Tokushima Fatty (OLETF) rats fed a high fructose diet (HFrD), with Long-Evans Tokushima Otsuka (LETO) rats used as a control. There were six groups: LETO, LETO-Allo, OLETF, OLETF-Allo, OLETF-HFrD, and OLETF-HFrD-Allo. HFrD significantly increased body weight, epididymal fat weight, and serum concentrations of UA, cholesterol, triglyceride, HbA1c, hepatic enzymes, HOMA-IR, fasting insulin, and two hour-glucose after intraperitoneal glucose tolerance tests, as well as NAFLD activity score of liver, compared to the OLETF group. Allopurinol treatment significantly reduced hepatic steatosis, epididymal fat, serum UA, HOMA-IR, hepatic enzyme levels, and cholesterol in the OLETF-HFrD-Allo group. Additionally, allopurinol significantly downregulated expression of lipogenic genes, upregulated lipid oxidation genes, downregulated hepatic pro-inflammatory cytokine genes, and decreased ER-stress induced protein expression, in comparison with the OLETF-HFrD group. In conclusion, allopurinol ameliorates HFrD-induced hepatic steatosis through modulation of hepatic lipid metabolism, inflammation, and ER stress pathway. UA may have a direct role in development of fructose-induced hepatic steatosis, and allopurinol could be a candidate for prevention or treatment of NAFLD.
► A simple method is presented for the fast identification and quantification of magnetite–maghemite mixture. ► The iron oxide nanoparticles produced by electrical wire explosion contained 55.8wt.% ...maghemite and 44.2wt.% magnetite. ► The method is expected to be extended to other binary mixture systems whose lattice parameters are very close.
The electrical explosion of Fe wire in air produced nanoparticles containing the binary mixture of magnetite (Fe3O4) and maghemite (γ-Fe2O3). The phase identification of magnetite and maghemite by the conventional X-ray diffraction method is not a simple matter because both have the same cubic structure and their lattice parameters are almost identical. Here, we propose a convenient method to assess the presence of magnetite–maghemite mixture and to further quantify its phase composition using the conventional peak deconvolution technique. A careful step scan around the high-angle peaks as (511) and (440) revealed the clear doublets indicative of the mixture phases. The quantitative analysis of the mixture phase was carried out by constructing a calibration curve using the pure magnetite and maghemite powders commercially available. The correlation coefficients, R2, for magnetite–maghemite mixture was 0.9941. According to the method, the iron oxide nanoparticles prepared by the wire explosion in this study was calculated to contain 55.8wt.% maghemite and 44.2wt.% magnetite. We believe that the proposed method would be a convenient tool for the study of the magnetite–maghemite mixture which otherwise requires highly sophisticated equipments and techniques.
To gain insights into the regulatory networks related to anthocyanin biosynthesis and identify key regulatory genes, we performed an integrated analysis of the transcriptome and metabolome in sprouts ...germinated from three colored potato cultivars: light-red Hongyoung, dark-purple Jayoung, and white Atlantic. We investigated transcriptional and metabolic changes using statistical analyses and gene–metabolite correlation networks. Transcript and metabolite profiles were generated through high-throughput RNA-sequencing data analysis and ultraperformance liquid chromatography quadrupole time-of-flight tandem mass spectrometry, respectively. The identification and quantification of changes in anthocyanin were performed using molecular formula-based mass accuracy and specific features of their MS² spectra. Correlation tests of anthocyanin contents and transcriptional changes showed 823 strong correlations (correlation coefficient, R²>0.9) between 22 compounds and 119 transcripts categorized into flavonoid metabolism, hormones, transcriptional regulation, and signaling. The connection network of anthocyanins and genes showed a regulatory system involved in the pigmentation of light-red Hongyoung and dark-purple Jayoung potatoes, suggesting that this systemic approach is powerful for investigations into novel genes that are potential targets for the breeding of new valuable potato cultivars.
Aims
This study was designed to investigate the association between pancreatic fat content (PFC) and insulin secretory capacity as well as glucose tolerance in Korean adults.
Materials
A total of 39 ...participants (mean age 49.9 years, 53% males) without a previous history of diabetes, or those previously diagnosed as having diabetes but with less than 10 years of disease duration and no medication history were included. They were stratified according to the results of the oral glucose tolerance test (OGTT): normal glucose tolerance, prediabetes, and diabetes.
Methods
All participants underwent the proton magnetic resonance spectroscopy (1H‐MRS) to assess PFC. Insulin sensitivity and β‐cell function were measured by the frequently sampled intravenous glucose tolerance tests (FSIVGTT) and OGTT‐derived indices.
Results
As glucose tolerance deteriorated, parameters such as Stumvoll index, oral glucose insulin sensitivity index, homeostatic model assessment (HOMA)‐β, insulinogenic index and oral disposition index from the OGTT, and acute insulin response to glucose (AIR) and disposition index (DI) from the FSIVGTT were decreased. PFC increased with deterioration in glucose tolerance (NGT: 12.0%, prediabetes: 23.7%, and diabetes: 31.9%). Correlation analysis indicated that glucose levels at 60 and 120 min during the OGTT were positively correlated with PFC. Also, there was a significant negative correlation between PFC and DI as well as AIR derived from the FSIVGTT.
Conclusions
PFC evaluated by 1H‐MRS in Korean adults was higher in those diagnosed with diabetes than those with normal glucose tolerance status. PFC also showed a significant negative correlation with indices reflecting beta cell function.
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•Microorganisms have been engineered to produce FAs from non-edible carbon sources.•Non-oleaginous microorganisms were engineered to produce FFAs.•Oleaginous microorganisms were also ...engineered to produce FFAs.•Biofuels and commodity chemicals have been produced by engineered FA overproducers.•Microbial production of FA-derived natural products has been demonstrated.
Microbial production of fatty acids and derivatives from non-edible biomass has attracted much attention as an alternative to their production from plant oils and animal fats. Fatty acids and some of their derivatives are ubiquitous metabolites synthesized for membrane biosynthesis and other metabolic purposes in microorganisms. These compounds, however, are rarely produced beyond cellular demands, frequently resulting in low titers even after metabolic engineering. Recently, more advanced metabolic engineering strategies including systems metabolic engineering allowed improved production of fatty acids and their derivatives by employing non-oleaginous and oleaginous microorganisms. Here, we review metabolic engineering strategies developed for the production of fatty acids and derivative chemicals by non-oleaginous and oleaginous microorganisms in recent years.
The established biomarker for hepatocellular carcinoma (HCC), serum α-fetoprotein (AFP), has suboptimal performance in early disease stages. This study aimed to develop a metabolite panel to ...differentiate early-stage HCC from cirrhosis. Cross-sectional metabolomic analyses of serum samples were performed for 53 and 47 patients with early HCC and cirrhosis, respectively, and 50 matched healthy controls. Results were validated in 82 and 80 patients with early HCC and cirrhosis, respectively. To retain a broad spectrum of metabolites, technically distinct analyses (global metabolomic profiling using gas chromatography time-of-flight mass spectrometry and targeted analyses using liquid chromatography with tandem mass spectrometry) were employed. Multivariate analyses classified distinct metabolites; logistic regression was employed to construct a prediction model for HCC diagnosis. Five metabolites (methionine, proline, ornithine, pimelylcarnitine, and octanoylcarnitine) were selected in a panel. The panel distinguished HCC from cirrhosis and normal controls, with an area under the receiver operating curve (AUC) of 0.82; this was significantly better than that of AFP (AUC: 0.75). During validation, the panel demonstrated significantly better predictability (AUC: 0.94) than did AFP (AUC: 0.78). Defects in ammonia recycling, the urea cycle, and amino acid metabolism, demonstrated on enrichment pathway analysis, may reliably distinguish HCC from cirrhosis. Compared with AFP alone, the metabolite panel substantially improved early-stage HCC detection.
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