With the escalation of plastic bans and restrictions, bio-based plastics, represented by polylactic acid (PLA), have become a major alternative to traditional plastics in the current market and are unanimously regarded as having potential for development. However, there are still several misconceptions about bio-based plastics, whose complete degradation requires specific composting conditions. Bio-based plastics might be slow to degrade when it is released into the natural environment. They might also be harmful to humans, biodiversity and ecosystem function as traditional petroleum-based plastics do. In recent years, with the increasing production capacity and market size of PLA plastics in China, there is an urgent need to investigate and further strengthen the management of the life cycle of PLA and other bio-based plastics. In particular, the in-situ biodegradability and recycling of hard-to-recycle bio-based plastics in the ecological environment should be focused. This review introduces the characteristics, synthesis and commercialization of PLA plastics, summarizes the current research progress of microbial and enzymatic degradation of PLA plastics, and discusses their biodegradation mechanisms. Moreover, two bio-disposal methods against PLA plastic waste, including microbial in-situ treatment and enzymatic closed-loop recycling, are proposed. At last, the prospects and trends for the development of PLA plastics are presented.
Humans ; Ecosystem ; Biodegradable Plastics ; Polyesters ; Biodegradation, Environmental

Although polyurethane (PUR) plastics play important roles in daily life, its wastes bring serious environmental pollutions. Biological (enzymatic) degradation is considered as an environmentally friendly and low-cost method for PUR waste recycling, in which the efficient PUR-degrading strains or enzymes are crucial. In this work, a polyester PUR-degrading strain YX8-1 was isolated from the surface of PUR waste collected from a landfill. Based on colony morphology and micromorphology observation, phylogenetic analysis of 16S rDNA and gyrA gene, as well as genome sequence comparison, strain YX8-1 was identified as Bacillus altitudinis. The results of high performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) showed that strain YX8-1 was able to depolymerize self-synthesized polyester PUR oligomer (PBA-PU) to produce a monomeric compound 4, 4'-methylene diphenylamine. Furthermore, strain YX8-1 was able to degrade 32% of the commercialized polyester PUR sponges within 30 days. This study thus provides a strain capable of biodegradation of PUR waste, which may facilitate the mining of related degrading enzymes.
Polyurethanes/chemistry* ; Polyesters/chemistry* ; Chromatography, Liquid ; Phylogeny ; Tandem Mass Spectrometry ; Bacteria/metabolism* ; Biodegradation, Environmental

With the environmental pollution caused by waste plastics becoming increasingly serious, biodegradable polyester has become the focus of public attention. Poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable polyester formed by the copolymerization of aliphatic and aromatic groups, which has excellent performance of both. The degradation of PBAT under natural conditions requires strict environmental conditions and long degradation cycle. To address these shortcomings, this study explored the application of cutinase in PBAT degradation and the impact of butylene terephthalate (BT) content on the biodegradability of PBAT, so as to improve the degradation rate of PBAT. Five Polyester degrading enzymes from different sources were selected to degrade PBAT to pick out the most efficient enzyme. Subsequently, the degradation rate of PBAT materials with different BT content were determined and compared. The results showed that cutinase ICCG was the best enzyme for PBAT biodegradation, and the higher the BT content, the lower the degradation rate of PBAT. Furthermore, the optimum temperature, buffer type, pH, the ratio of enzyme to substrate (E/S) and substrate concentration in the degradation system were determined to be 75 ℃, Tris HCl, 9.0, 0.4% and 1.0% respectively. These findings may facilitate the application of cutinase in PBAT degradation.
Polyesters/chemistry* ; Adipates

The present study aimed to unravel the carbon metabolism pathway of Acinetobacter sp. TAC-1, a heterotrophic nitrification-aerobic denitrification (HN-AD) strain that utilizes poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as a carbon source. Sodium acetate was employed as a control to assess the gene expression of carbon metabolic pathways in the TAC-1 strain. The results of genome sequencing demonstrated that the TAC-1 strain possessed various genes encoding carbon metabolic enzymes, such as gltA, icd, sucAB, acs, and pckA. KEGG pathway database analysis further verified the presence of carbon metabolism pathways, including the glycolytic pathway (EMP), pentose phosphate pathway (PPP), glyoxylate cycle (GAC), and tricarboxylic acid (TCA) cycle in the TAC-1 strain. The differential expression of metabolites derived from distinct carbon sources provided further evidence that the carbon metabolism pathway of TAC-1 utilizing PHBV follows the sequential process of PHBV (via the PPP pathway)→gluconate (via the EMP pathway)→acetyl-CoA (entering the TCA cycle)→CO₂+H₂O (generating electron donors and releasing energy). This study is expected to furnish a theoretical foundation for the advancement and implementation of novel denitrification processes based on HN-AD and solid carbon sources.
3-Hydroxybutyric Acid ; Carbon/metabolism* ; Polyesters ; Hydroxybutyrates ; Metabolic Networks and Pathways

OBJECTIVE: To investigate the effect of folic acid coated-crosslinked urethane-doped polyester elastomer (fCUPE) nerve conduit in repairing long distance peripheral nerve injury. METHODS: Thirty-six 3-month-old male Sprague Dawley rats weighing 180-220 g were randomly assigned to 3 groups, each consisting of 12 rats: CUPE nerve conduit transplantation group (group A), fCUPE nerve conduit transplantation group (group B), and autologous nerve transplantation group (group C), the contralateral healthy limb of group C served as the control group (group D). A 20-mm-long sciatic nerve defect model was established in rats, and corresponding materials were used to repair the nerve defect according to the group. The sciatic function index (SFI) of groups A-C was calculated using the Bain formula at 1, 2, and 3 months after operation. The nerve conduction velocity (NCV) of the affected side in groups A-D was assessed using neuroelectrophysiological techniques. At 3 months after operation, the regenerated nerve tissue was collected from groups A-C for S-100 immunohistochemical staining and Schwann cell count in groups A and B to compare the level of nerve repair and regeneration in each group. RESULTS: At 3 months after operation, the nerve conduits in all groups partially degraded. There was no significant adhesion between the nerve and the conduit and the surrounding tissues, the conduit was well connected with the distal and proximal nerves, and the nerve-like tissues in the conduit could be observed when the nerve conduit stents were cut off. SFI in group A was significantly higher than that in group C at each time point after operation and was significantly higher than that in group B at 2 and 3 months after operation ( P<0.05). There was no significant difference in SFI between groups B and C at each time point after operation ( P>0.05). NCV in group A was significantly slower than that in the other 3 groups at each time point after operation ( P<0.05). The NCV of groups B and C were slower than that of group D, but the difference was significant only at 1 month after operation ( P<0.05). There was no significant difference between groups B and C at each time point after operation ( P>0.05). Immunohistochemical staining showed that the nerve tissue of group A had an abnormal cavo-like structure, light tissue staining, and many non-Schwann cells. In group B, a large quantity of normal neural structures was observed, the staining was deeper than that in group A, and the distribution of dedifferentiated Schwann cells was obvious. In group C, the nerve bundles were arranged neatly, and the tissue staining was the deepest. The number of Schwann cells in group B was (727.50±57.60) cells/mm ², which was significantly more than that in group A [(298.33±153.12) cells/mm ²] ( t=6.139, P<0.001). CONCLUSION The fCUPE nerve conduit is effective in repairing long-distance sciatic nerve defects and is comparable to autologous nerve grafts. It has the potential to be used as a substitute material for peripheral nerve defect transplantation.
Rats ; Animals ; Male ; Rats, Sprague-Dawley ; Polyesters ; Peripheral Nerve Injuries/surgery* ; Elastomers ; Urethane ; Sciatic Nerve/injuries* ; Carbamates ; Nerve Tissue ; Nerve Regeneration/physiology*

The composite material PLGA compounded with β-tricalcium phosphate (β-TCP) was prepared by melt blending method, and the absorbable interface screw was prepared by injection molding process. Prepare PBS buffer that simulates human body, conduct in vitro degradation experiments on interface screws according to relevant national and industry standards, then test and characterize interface screws at different time points for degradation of intrinsic viscosity, average molecular weight distribution, mass loss, mechanical properties and thermal properties. According to the degradation performance-time curve, determine the time node at which the interface screw loses the mechanical properties. In this paper, the in vitro degradation behavior of interfacial screws prepared from PLGA and β-TCP composites was studied in detail, providing a reference and basis for the degradation behavior of absorbable products prepared from PLGA and β-TCP composites.
Humans ; Polyesters ; Materials Testing ; Calcium Phosphates ; Absorbable Implants

Objective: To explore the diagnostic value and model of serum Golgi protein 73 (GP73) in patients with hepatitis C cirrhosis. Methods: 271 cases with chronic hepatitis C virus infection who were treated in the Fifth Medical Center of PLA General Hospital from January 2010 to December 2017 were retrospectively collected as the research objects, including 126 cases with hepatitis and 145 cases with liver cirrhosis. Serum GP73 and liver stiffness measurement (LSM) based on transient elastography test were performed in all patients. Simultaneously, blood routine, liver function, coagulation function and other related indicators were collected. GP73 diagnostic efficiency for liver cirrhosis was evaluated by receiver operating characteristic curve (ROC). GP73 diagnostic value was clarified after comparison with aspartate aminotransferase/platelet ratio index (APRI), FIB-4 index (FIB-4) and LSM. Compensated hepatitis C virus-related cirrhosis diagnostic model based on serological index was established by logistic regression analysis. Results: The area under the receiver operating characteristic curve (AUC) of GP73, LSM, FIB-4 and APRI in the diagnosis of compensated hepatitis C virus-related cirrhosis were 0.923, 0.839, 0.836 and 0.800 respectively, and GP73 had the best diagnostic efficiency (P <0.001). LSM and GP73 combined use had improved the diagnostic sensitivity of cirrhosis to 97.24%. Multivariate logistic regression analysis revealed that GP73, age, and platelets were independent predictors of cirrhosis.Compensated hepatitis C virus-related cirrhosis diagnostic model (GAP) was established based on the result: LogitP=1/[1+exp(6.145+0.013×platelet-0.059×age-0.059×GP73)].AUC model for diagnosing compensated liver cirrhosis was 0.944, and the optimal cut-off value was 0.56, with sensitivity and specificity of 84.03% and 92.06%, respectively, and the diagnostic efficiency of this model was better than that of APRI, FIB-4, LSM and GP73 alone (P<0.05). Conclusion: GP73 is a reliable serum biomarker for the diagnosis of compensated hepatitis C virus-related cirrhosis. The GAP diagnostic model based on GP73, platelet count, and age can further improve the diagnostic efficiency and help to diagnose patients with compensated hepatitis C virus-related cirrhosis.
Aspartate Aminotransferases ; Biomarkers ; Fibrosis ; Hepatitis C ; Hepatitis C, Chronic/complications* ; Humans ; Infant, Newborn ; Liver/pathology* ; Liver Cirrhosis/pathology* ; Polyesters ; ROC Curve ; Retrospective Studies

Objective: To investigate the expression and function of collagen type ⅩⅦ α1 (COL17α1) in aging mouse skin and its effect on the stemness and proliferation of human epidermal stem cells (ESCs), and to explore the mechanism of related microRNA (miR) in intervening the expression of COL17α1 of human ESC. Methods: The method of experimental research was used. Twelve 2-month-old (young) and twelve 24-month-old (aged) male C57BL/6J mice were selected, and full-thickness skin samples from their upper back were taken for follow-up detection. After hematoxylin-eosin staining of the full-thickness skin samples of young mice and aged mice, the structure of the epidermis was observed and the thickness of the epidermis was measured; the morphology of epidermal basement membrane and hemidesmosomes were observed by transmission electron microscopy, and the hemidesmosomes were counted; the mRNA and protein expressions of COL17α1 were detected by real-time fluorescent quantitative reverse transcription polymerase chain reaction (RT-PCR) and Western blotting respectively, and the protein expression and distribution of COL17α1 was observed and detected by immunofluorescence method. The fresh foreskin tissue discarded after surgery was obtained from 3 healthy men aged 20-30 years who underwent circumcision at the Fourth Medical Center of PLA General Hospital, ESCs were extracted and well-grown cells were wsed for follow-up experiments. According to the random number table (the same grouping method below), ESCs were divided into blank control group, transfection reagent control group, empty vector plasmid group, and COL17α1 knockdown plasmid group with corresponding treatment. After 48 hours of culture, the mRNA expression of COL17α1 was detected by real-time fluorescent quantitative RT-PCR, the protein expressions of COL17α1 and cytokeratin 14 (CK14) were detected by Western blotting, and the cell proliferation level was detected by cell counting kit 8. miRs that might act on the 3' non-coding region of COL17α1 mRNA were screened through DIANA, miRTarBase, miRNAMap, TargetScan, and microRNA databases. The ESCs were divided into negative control group transfected with miR mimic negative control and each miR mimic group transfected with each of the previously screened miR mimics. Forty-eight hours after transfection, the protein expression of COL17α1 was detected by Western blotting. Based on the sequencing data set GSE114006 in Gene Expression Omnibus (GEO), the GEO2R tool was used to statistically analyze the expression of the previously screened miRs that could cause the reduction of COL17α1 protein expression in the skin of 30 young (18-25 years old) and 30 elderly (>70 years old) human skins. The full-thickness skin samples of young mice and aged mice were taken, and the expressions of increased miRs in the aforementioned aged human skin were detected by real-time fluorescent quantitative RT-PCR. Two batches of human ESCs were taken, the first batch was divided into COL17α1 wild type+miR-203b-3p negative control group and COL17α1 wild type+miR-203b-3p mimic group, and the second batch was divided into COL17α1 mutant+miR-203b-3p negative control group and COL17α1 mutant+miR-203b-3p mimic group. Each group of ESC was transfected with corresponding sequences respectively. Forty-eight hours later, the luciferase reporter gene detection kit was used to detect the gene expression level of COL17α1. The number of samples in the tissue experiment was 6, and the number of samples in the cell experiment was 3. Data were statistically analyzed with independent sample t test, one-way analysis of variance, least significant difference test or Dunnett's test, Mann-Whitney U test or Kruskal-Wallis H test. Results: Compared with those of young mice, the boundary between the epidermis and the dermis of the aged mice skin was blurred and the cell layers were less, and the thickness of epidermis was significantly thinner (Z=-2.88, P<0.01); the morphology of basement membrane was discontinuous, with less unevenly distributed hemidesmosomes at the epidermis-dermis junction, and the number of hemidesmosomes was significantly reduced (Z=-2.91, P<0.01); the mRNA and protein expression levels of COL17α1 in the skin of aged mice were significantly decreased (with t values of 10.61 and 6.85, respectively, P<0.01). Compared with those of young mice, the protein expression of COL17α1 in the basal layer of epidermis and the bulb of hair follicle in the skin of aged mice was significantly decreased (Z=-2.24, P<0.05). After 48 hours of culture, the protein expression levels of COL17α1 in ESCs of blank control group, transfection reagent control group, empty vector plasmid group, and COL17α1 knockdown plasmid group were 1.00±0.27, 1.12±0.21, 1.13±0.23, and 0.42±0.18, respectively. Compared with those of blank control group, the mRNA and protein expression levels of COL17α1, the protein expression level of CK14, and the proliferation level of ESCs in transfection reagent control group and empty vector plasmid group did not change significantly (P>0.05), while these indexes in COL17α1 knockdown plasmid group were significantly decreased (P<0.05 or P<0.01). miR-203a-3p, miR-203b-3p, miR-512-5p, miR-124-3p, miR-28-5p, miR-590-3p, and miR-329-5p might bind to the 3' non-coding region of COL17α1 mRNA. Forty-eight hours after transfection, compared with 1.000±0.224 in negative control group, the protein expression level of COL17α1 in ESCs of miR-329-5p mimic group, miR-203b-3p mimic group, and miR-203a-3p mimic group decreased significantly (0.516±0.188, 0.170±0.025, and 0.235±0.025, with t values of 3.17, 5.43, and 5.07, respectively, P<0.05 or P<0.01). Only the expression level of miR-203b-3p in the skin of the elderly was significantly higher than that of the young (t=3.27, P<0.01). The expression level of miR-203b-3p in the skin of aged mice was significantly higher than that of young mice (Z=-2.88, P<0.01). Forty-eight hours after transfection, the gene expression level of COL17α1 in ESCs of COL17α1 wild type+miR-203b-3p mimic group was significantly lower than that of COL17α1 wild type+miR-203b-3p negative control group (t=7.66, P<0.01). The gene expression level of COL17α1 in ESCs of COL17α1 mutant+miR-203b-3p mimic group was similar to that of COL17α1 mutant+miR-203b-3p negative control group (P>0.05). Conclusions: The mRNA and protein expression levels of COL17α1 decrease with age increasing in mice, which may lead to the detachment of mouse ESC from the epidermal basement membrane. Decreased expression of COL17α1 can inhibit the expression of CK14 and ESC proliferation, which may be responsible for the thinning of the epidermis and slower wound healing in aged human skin. The increased expression of miR-203b-3p in aged mouse skin can target and bind to the 3' non-coding region of COL17α1 mRNA, hindering the post-transcriptional translation process, thus resulting in decreased COL17α1 protein expression.
Adolescent ; Adult ; Aged ; Animals ; Autoantigens ; Humans ; Keratin-14 ; Male ; Mice ; Mice, Inbred C57BL ; MicroRNAs/genetics* ; Non-Fibrillar Collagens/pharmacology* ; Polyesters ; RNA, Messenger ; Skin Aging ; Stem Cells ; Young Adult

Polyhydroxyalkanoates (PHAs) have obtained much attention in biomaterial fields due to their similar physicochemical properties to those of the petroleum-derived plastics. Poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] is one member of the PHAs family, and has better toughness and transparency compared to existing polylactic acid (PLA) and poly[(R)-3-hydroxybutyrate] [P(3HB)]. First, we confirmed the one-step biosynthesis of P(LA-co-3HB) with the lactate fraction of 23.8 mol% by introducing P(3HB-co-LA) production module into Escherichia coli MG1655. Then, the lactate fraction was increased to 37.2 mol% in the dld deficient strain WXJ01-03. The genes encoding the thioesterases, ydiI and yciA, were further knocked out, and the lactate fraction in the P(3HB-co-LA) was improved to 42.3 mol% and 41.1 mol% respectively. Strain WXJ03-03 with dld, ydiI and yciA deficient was used for the production of the LA-enriched polymer, and the lactate fraction was improved to 46.1 mol%. Notably, the lactate fraction in P(3HB-co-LA) from xylose was remarkably higher than from glucose, indicating xylose as a potent carbon source for P(3HB-co-LA) production. Therefore, the deficiency of thioesterase may be considered as an effective strategy to improve the lactate fraction in P(3HB-co-LA) in xylose fermentation.
Escherichia coli/genetics* ; Hydroxybutyrates ; Lactic Acid ; Polyesters ; Polyhydroxyalkanoates ; Xylose

Polyhydroxyalkanoate (PHA) is a family of biodegradable polyesters synthesized by microorganisms. It has various monomer structures and physical properties with broad application prospects. However, its large-scale production is still hindered by the high cost. In the past 30 years, metabolic engineering approach has been used to tune the metabolic flux, engineer and introduce pathways. The efficiency of PHA synthesis by microorganisms has been significantly improved, and the diversity of PHA monomer, structure and substrate have also been enriched. Meanwhile, by changing cell morphology and PHA particle size, more efficient downstream production process has achieved and PHA production costs have been reduced. In recent years, "Next generation industrial biotechnology" (NGIB) based on extremophiles, especially halophilic Halomonas spp., has been rapidly developed. NGIB has achieved the opening and continuous production of PHA, which simplifies the production process and saves energy and fresh water. Combined with metabolic engineering, Halomonas spp. can be transformed into low-cost production platform of numerous PHA. It is expected to improve the market competitiveness and promote the commercialization of PHA.
Biotechnology ; Halomonas/genetics* ; Metabolic Engineering ; Polyesters ; Polyhydroxyalkanoates