ß-Ketoadipic acid production from poly(ethylene terephthalate) waste via chemobiological upcycling.

The upcycling of poly(ethylene terephthalate) (PET) waste can simultaneously produce value-added chemicals and reduce the growing environmental impact of plastic waste. In this study, we designed a chemobiological system to convert terephthalic acid (TPA), an aromatic monomer of PET, to ß-ketoadipic acid (ßKA), a C6 keto-diacid that functions as a building block for nylon-6,6 analogs. Using microwave-assisted hydrolysis in a neutral aqueous system, PET was converted to TPA with Amberlyst-15, a conventional catalyst with high conversion efficiency and reusability. The bioconversion process of TPA into ßKA used a recombinant Escherichia coli ßKA expressing two conversion modules for TPA degradation (tphAabc and tphB) and ßKA synthesis (aroY, catABC, and pcaD). To improve bioconversion, the formation of acetic acid, a deleterious factor for TPA conversion in flask cultivation, was efficiently regulated by deleting the poxB gene along with operating the bioreactor to supply oxygen. By applying two-stage fermentation consisting of the growth phase in pH 7 followed by the production phase in pH 5.5, a total of 13.61 mM ßKA was successfully produced with 96% conversion efficiency. This efficient chemobiological PET upcycling system provides a promising approach for the circular economy to acquire various chemicals from PET waste.

Recent advances in microbial production of diamines, aminocarboxylic acids, and diacids as potential platform chemicals and bio-based polyamides monomers.

Recently, bio-based manufacturing processes of value-added platform chemicals and polymers in biorefineries using renewable resources have extensively been developed for sustainable and carbon dioxide (CO2) neutral-based industry. Among them, bio-based diamines, aminocarboxylic acids, and diacids have been used as monomers for the synthesis of polyamides having different carbon numbers and ubiquitous and versatile industrial polymers and also as precursors for further chemical and biological processes to afford valuable chemicals. Until now, these platform bio-chemicals have successfully been produced by biorefinery processes employing enzymes and/or microbial host strains as main catalysts. In this review, we discuss recent advances in bio-based production of diamines, aminocarboxylic acids, and diacids, which has been developed and improved by systems metabolic engineering strategies of microbial consortia and optimization of microbial conversion processes including whole cell bioconversion and direct fermentative production.

Microbial production of 2-pyrone-4,6-dicarboxylic acid from lignin derivatives in an engineered Pseudomonas putida and its application for the synthesis of bio-based polyester.

Lignin valorization depends on microbial upcycling of various aromatic compounds in the form of a complex mixture, including p-coumaric acid and ferulic acid. In this study, an engineered Pseudomonas putida strain utilizing lignin-derived monomeric compounds via biological funneling was developed to produce 2-pyrone-4,6-dicarboxylic acid (PDC), which has been considered a promising building block for bioplastics. The biosynthetic pathway for PDC production was established by introducing the heterologous ligABC genes under the promoter Ptac in a strain lacking pcaGH genes to accumulate a precursor of PDC, i.e., protocatechuic acid. Based on the culture optimization, fed-batch fermentation of the final strain resulted in 22.7 g/L PDC with a molar yield of 1.0 mol/mol and productivity of 0.21 g/L/h. Subsequent purification of PDC at high purity was successfully implemented, which was consequently applied for the novel polyester.

Chemo-Biological Upcycling of Poly(ethylene terephthalate) to Multifunctional Coating Materials.

Chemo-biological upcycling of poly(ethylene terephthalate) (PET) developed in this study includes the following key steps: chemo-enzymatic PET depolymerization, biotransformation of terephthalic acid (TPA) into catechol, and its application as a coating agent. Monomeric units were first produced through PET glycolysis into bis(2-hydroxyethyl) terephthalate (BHET), mono(2-hydroxyethyl) terephthalate (MHET), and PET oligomers, and enzymatic hydrolysis of these glycolyzed products using Bacillus subtilis esterase (Bs2Est). Bs2Est efficiently hydrolyzed glycolyzed products into TPA as a key enzyme for chemo-enzymatic depolymerization. Furthermore, catechol solution produced from TPA via a whole-cell biotransformation (Escherichia coli) could be directly used for functional coating on various substrates after simple cell removal from the culture medium without further purification and water-evaporation. This work demonstrates a proof-of-concept of a PET upcycling strategy via a combination of chemo-biological conversion of PET waste into multifunctional coating materials.

Recent Advances in Sustainable Plastic Upcycling and Biopolymers.

Advances in scientific technology in the early twentieth century have facilitated the development of synthetic plastics that are lightweight, rigid, and can be easily molded into a desirable shape without changing their material properties. Thus, plastics become ubiquitous and indispensable materials that are used in various manufacturing sectors, including clothing, automotive, medical, and electronic industries. However, strong physical durability and chemical stability of synthetic plastics, most of which are produced from fossil fuels, hinder their complete degradation when they are improperly discarded after use. In addition, accumulated plastic wastes without degradation have caused severe environmental problems, such as microplastics pollution and plastic islands. Thus, the usage and production of plastics is not free from environmental pollution or resource depletion. In order to lessen the impact of climate change and reduce plastic pollution, it is necessary to understand and address the current plastic life cycles. In this review, "sustainable biopolymers" are suggested as a promising solution to the current plastic crisis. The desired properties of sustainable biopolymers and bio-based and bio/chemical hybrid technologies for the development of sustainable biopolymers are mainly discussed.

Biosynthesis of polyhydroxyalkanoates from sucrose by metabolically engineered Escherichia coli strains.

Sucrose utilization has been established in Escherichia coli strains by expression of Mannheimia succiniciproducens ß-fructofuranosidase (SacC), which hydrolyzes sucrose into glucose and fructose. Recombinant E. coli strains that can utilize sucrose were examined for their abilities to produce poly(3-hydroxybutyrate) [P(3HB)] and poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] from sucrose. When recombinant E. coli strains expressing Ralstonia eutropha PhaCAB and SacC were cultured in MR medium containing 20 g/L of sucrose, all recombinant E. coli strains could produce P(3HB) from sucrose. Also, recombinant E. coli strains expressing Pseudomonas sp. MBEL 6-19 PhaC1437, Clostridium propionicum Pct540, R. eutropha PhaAB enzymes along with SacC could produce P(3HB-co-LA) from sucrose. Among the examined E. coli strains, recombinant E. coli XL1-Blue produced the highest contents of P(3HB) (53.60 ± 2.55 wt%) and P(3HB-co-LA) (29.44 ± 0.39 wt%). In the batch fermentations, recombinant E. coli XL1-Blue strains completely consumed 20 g/L of sucrose as the sole carbon source and supported the production of 3.76 g/L of P(3HB) and 1.82 g/L of P(3HB-co-LA) with 38.21 wt% P(3HB) and 20.88 wt% P(3HB-co-LA) contents, respectively. Recombinant E. coli strains developed in this study can be used to establish a cost-efficient biorefinery for the production of polyhydroxyalkanoates (PHAs) from sucrose, which is an abundant and inexpensive carbon source.

Learning, memory deficits, and impaired neuronal maturation attributed to acrylamide.

Acrylamide (ACR) is a neurotoxin known to produce neurotoxicity characterized by ataxia, skeletal muscle weakness, cognitive impairment, and numbness of the extremities. Previously, investigators reported that high-dose (50 mg/kg) ACR impaired hippocampal neurogenesis and increased neural progenitor cell death; however, the influence of subchronic environmentally relevant low dose-(2, 20, or 200 µg/kg) ACRs have not been examined in adult neurogenesis or cognitive function in mice. Accordingly, the aim of the present study was to investigate whether low-dose ACR adversely affected mouse hippocampal neurogenesis and neurocognitive functions. Male C57BL/6 mice were orally administered vehicle or ACR at 2, 20, or 200 µg/kg/day for 4 weeks. ACR did not significantly alter the number of newly generated cells or produce neuroinflammation or neuronal loss in hippocampi. However, behavioral studies revealed that 200 µg/kg ACR produced learning and memory impairment. Furthermore, incubation of ACR with primary cultured neurons during the developmental stage was found to delay neuronal maturation without affecting cell viability indicating the presence of developmental neurotoxicity. These findings indicate that although exposure to in vivo low-dose ACR daily for 4 weeks exerted no apparent marked effect on hippocampal neurogenesis, in vitro observations in primary cultured neurons noted adverse effects on learning and memory impairment suggestive of neurotoxic actions.

Association of CLOCK, ARNTL, PER2, and GNB3 polymorphisms with diurnal preference in a Korean population.

Polymorphisms in human circadian genes are potential genetic markers that affect diurnal preference in several populations. In this study, we evaluated whether four polymorphisms in circadian genes CLOCK, ARNTL, PER2, and GNB3 were associated with diurnal preference in a Korean population. In all, 499 healthy subjects were genotyped for four functional polymorphisms in CLOCK, ARNTL, PER2, and GNB3. Composite scale of morningness (CSM) was applied to measure phenotype patterns of human diurnal preference. In addition, three subscale scores, i.e. "morningness," "activity planning," and "morning alertness," were extracted from the CSM. No significant associations were observed between CSM scores and CLOCK (rs1801260) genotype or T allele carrier status, CSM scores and ARNTL (rs2278749) C allele carrier status, and CSM scores and GNB3 (rs5443) genotype or C allele carrier status. However, total CSM scores and scores of its subscales were significantly associated with PER2 (rs934945) genotype (p = 0.010, p = 0.018, and p = 0.005 for total, morningness, and activity planning, respectively) and G allele carrier status (p = 0.003, p = 0.005, and p = 0.002 for total, morningness, and activity planning, respectively). The best model result obtained by performing multifactor dimensionality reduction analysis ([Formula: see text]2 = 11.2798, p = 0.0008) indicated that interaction among C/T single nucleotide polymorphism (SNP) in ARNTL, C/T SNP in GNB3, and G/A SNP in PER2 synergistically affected the risk associated with diurnal preference toward eveningness. These results suggest that circadian gene PER2 is associated with diurnal preference in healthy Korean population. Although polymorphisms in ARNTL and GNB3 were not significantly associated with diurnal preference, their interactions with the polymorphism in PER2 may synergistically increase the risk of diurnal preference toward eveningness.

Association of CLOCK, ARNTL, and NPAS2 gene polymorphisms and seasonal variations in mood and behavior.

Seasonal affective disorder (SAD) is a condition of seasonal mood changes characterized by recurrent depression in autumn or winter that spontaneously remits in spring or summer. Evidence has suggested that circadian gene variants contribute to the pathogenesis of SAD. In this study, we investigated polymorphisms in the CLOCK, ARNTL, and NPAS2 genes in relation to seasonal variation in 507 healthy young adults. Seasonal variations were assessed with the Seasonality Pattern Assessment Questionnaire. The prevalence of SAD was 12.0% (winter-type 9.3%, summer-type 2.8%). No significant difference was found between the groups in the genotype distribution of ARNTL rs2278749 and NPAS2 rs2305160. The T allele of CLOCK rs1801260 was significantly more frequent in seasonals (SAD + subsyndromal SAD) compared with non-seasonals (p = 0.020, odds ratio = 1.89, 95% confidence interval = 1.09-3.27). Global seasonality score was significantly different among genotypes of CLOCK rs1801260, but not among genotypes of ARNTL rs2278749 and NPAS2 rs2305160. However, statistical difference was observed in the body weight and appetite subscales among genotypes of ARNTL rs2278749 and in the body weight subscale among genotypes of NPAS2 rs2305160. There was synergistic interaction between CLOCK rs1801260 and ARNTL rs2278749 on seasonality. To our knowledge, this study is the first to reveal an association between the CLOCK gene and seasonal variations in mood and behavior in the Korean population. Although we cannot confirm previous findings of an association between SAD and the ARNTL and NPAS2 genes, these genes may influence seasonal variations through metabolic factors such as body weight and appetite. The interaction of the CLOCK and ARNTL genes contributes to susceptibility for SAD.

A hemagglutinin quantification method for development of an influenza pandemic vaccine using size exclusion high performance liquid chromatography.

Single radial immunodiffusion (SRID) assay requires a reference antigen and an antibody to the hemagglutinin (HA) of an influenza vaccine. As it takes 2­3 months to develop the reference antigen, vaccine development is delayed in cases of an influenza pandemic. In the present study, the measurement of the HA content of influenza vaccines was assessed using size exclusion high performance liquid chromatography (SE­HPLC) for the rapid development of a pandemic vaccine. When the 2009 H1N1 reference antigen, pandemic 2009 H1N1 vaccine and 2010 seasonal influenza vaccines were analyzed by SE­HPLC, the HA of the reference antigen and vaccines was specifically separated. The presence and specificity of HA were evidenced with immunoprecipitation and ELISA assays. For the influenza vaccines, the chromatogram pattern and retention time of HA were similar among the antigen types (2009 H1N1, 2010 H3N2 and 2010 B). In addition, when SE­HPLC was applied, the ratio of HA chromatogram to peak area revealed a significant correlation with HA concentration for the reference antigen and vaccine. The result of the HA content calculation based on SE­HPLC exhibited 99.91­100% similarity, compared with that of SRID. These findings suggest that the measurement of peak area ratio/HA content using SE­HPLC may be a substitute for SRID and rapidly measure HA content to enable faster development of a vaccine during an influenza pandemic.

Clinical characteristics of the respiratory subtype in panic disorder patients.

OBJECTIVE: Panic disorder has been suggested to be divided into the respiratory and non-respiratory subtypes in terms of its clinical presentations. The present study aimed to investigate whether there are any differences in treatment response and clinical characteristics between the respiratory and non-respiratory subtypes of panic disorder patients. METHODS: Among the 48 patients those who completed the study, 25 panic disorder patients were classified as the respiratory subtype, whereas 23 panic disorder patients were classified as the non-respiratory subtype. All patients were treated with escitalopram or paroxetine for 12 weeks. We measured clinical and psychological characteristics before and after pharmacotherapy using the Panic Disorder Severity Scale (PDSS), Albany Panic and Phobic Questionnaire (APPQ), Anxiety Sensitivity Index-Revised (ASI-R), State-Trait Anxiety Inventory (STAI-T, STAI-S), Hamilton Anxiety Rating Scale (HAM-A), and Hamilton Depression Rating Scale (HAM-D). RESULTS: The prevalence of the agoraphobia was significantly higher in the respiratory group than the non-respiratory group although there were no differences in gender and medication between the two groups. The respiratory group showed higher scores on the fear of respiratory symptoms of the ASI-R. In addition, after pharmacotherapy, the respiratory group showed more improvement in panic symptoms than the non-respiratory group. CONCLUSION: Panic disorder patients with the respiratory subtype showed more severe clinical presentations, but a greater treatment response to SSRIs than those with non-respiratory subtype. Thus, classification of panic disorder patients as respiratory and non-respiratory subtypes may be useful to predict clinical course and treatment response to SSRIs.