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

In this review, we presented the industrial status of biomanufactured polyhydroxyalkanoates (PHA), including poly (3-hydroxybutyrate) (PHB), poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly (3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB)), and poly (3-hydroxybutyrate-3-hydroxycaproate) (PHBH). A lot of modification studies, aimed at solving problems of poor thermal stability, narrow processing window and other drawbacks of PHA, are discussed. The properties of PHA can be optimized by using proper modification method, in order to expand its applications.
3-Hydroxybutyric Acid ; Biotechnology ; Hydroxybutyrates ; Polyesters ; Polyhydroxyalkanoates ; chemistry

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

pH and temperature sensitive biodegradable block copolymers are some macromolecules connected by biodegradable materials and pH sensitive monomers according to a certain sequence, or biodegradable polyesters polymerized themselves. On the basis of pertinent documents, the development of pH and temperature sensitive biodegradable block copolymers was introduced, involving their mechanism of action and potential application. PH and temperature sensitive biodegradable block copolymers could control the drug release rate freely, avoiding burst effect. Besides, the biocompatibility of these biodegradable materials is also excellent. So the use of pH and temperature sensitive biodegradable block copolymers as biodegradable drug delivery devices has attracted considerable interest in the intelligent drug delivery system.
Biocompatible Materials ; chemistry ; Drug Delivery Systems ; Hydrogen-Ion Concentration ; Lactates ; chemistry ; Lactic Acid ; chemistry ; Polyesters ; chemistry ; Polyethylene Glycols ; chemistry ; Polyglactin 910 ; chemistry ; Polyglycolic Acid ; chemistry ; Polymers ; chemistry ; Temperature

In recent years, bio-based materials are becoming a new dominant industry leading the scientific and technological innovation, and economic development of the world. We reviewed the new development of bio-based materials industry in China, analyzed the entire market of bio-based materials products comprehensively, and also stated the industry status of bio-based chemicals, such as lactic acid, 1,3-propanediol, and succinic acid; biodegradable bio-based polymers, such as co-polyester of diacid and diol, polylactic acid, carbon dioxide based copolymer, polyhydroxyalknoates, polycaprolactone, and thermoplastic bio-based plastics; non-biodegradable bio-based polymers, such as bio-based polyamide, polytrimethylene terephthalate, bio-based polyurethane, and bio-based fibers.
Biomass ; Biotechnology ; China ; Lactic Acid ; Phthalic Acids ; Plastics ; Polyesters ; Polyhydroxyalkanoates ; Polymers ; Propylene Glycols ; Succinic Acid

This paper reviews the research and commercialization progresses of biobased polymeric materials including polyhydroxyalkanoates (PHA), polylactides (PLA), poly (butylene succinate) (PBS) and its monomer succinate, and CO2 copolymer poly (propylene carbonate), especially these efforts made in China.
Bioengineering ; Butylene Glycols ; China ; Polyesters ; Polyhydroxyalkanoates ; Polymers ; Propane ; analogs & derivatives ; Succinic Acid

The purpose of this study was to evaluate the difference of surface roughness of composite resin according to composite resin type, polishing methods, and use of resin sealant. Two hundred rectangular specimens, sized 8 x 3 x 2 mm, were made of Micro-new (Bisco, Inc., Schaumburg, IL, U.S.A) and Filtek Supreme (3M ESPE Dental Products, St. Paul, MN, U.S.A.), and divided into two groups; Micronew-M group, Filtek Supreme-S group. Specimens for each composite group were subdivided into five groups by finishing and polishing instruments used; M1 & S1 (polyester strip), M2 & S2 (Sof-Lex disc), M3 & S3 (Enhance disc and polishing paste), M4 & S4 (Astropol), and M5 & S5 (finishing bur). Polished groups were added letter B after the application of resin surface sealant (Biscover), eg, M1B and S1B. After specimens were stored with distilled water for 24 hr, average surface roughness (Ra) was taken using a surface roughness tester. Representative specimens of each group were examined by FE-SEM (S-4700: Hitachi High Technologies Co., Tokyo, Japan). The data were analysed using paired t-test, ANOVA and Duncan's tests at the 0.05 probability level. The results of this study were as follows; 1. The lowest Ra was achieved in all groups using polyester strip and the highest Ra was achieved in M5, S5 and M5B groups using finishing bur. On FE-SEM, M1 and S1 groups provided the smoothest surfaces, M5 and S5 groups were presented the roughest surfaces and voids by debonding of filler on the polished specimens. 2. There was no significant difference in Ra between Micronew and Filtek Supreme before the application of resin sealant, but Micronew was smoother than Filek Supreme after the application of resin sealant. 3. There was significant corelation between Ra of type of composite resin and polishing methods before the application of resin sealant (p = 0.000), but no significant interaction between them after the application of resin sealant. On FE-SEM, most of composite resin surfaces were smooth after the application of resin sealant on the polished specimens. 4. Compared with before and after the application of resin sealant in group treated in the same composite and polishing methods, Ra of M4B and M5B was statistically lower than that of M4 and M5, and S5B was lower than that of S5, respectively (p < 0.05). In conclusion, surface roughness by polishing instruments was different according to type of composite resin. Overall, polyester strip produced the smoothest surface, but finishing bur produced the roughest surface. Application of resin sealant provided the smooth surfaces in specimens polished with Enhance, Astropol and finishing bur, but not provided them in specimens polished with Sof-Lex disc.
Polyesters ; Water

PURPOSE: The purpose of this study was to evaluate the machining accuracy and consistency of implant/abutment/screw combination of internal connection type. MATERIAL AND METHODS: In this study, each two randomly selected internal implant fixtures from ITI, 3i, Avana, Bicon, Friadent, Astra, and Paragon system were used. Each abutment was connected to the implant with 32Ncm torque value using a digital torque controller or tapping. All samples were cross-sectioned with grinder-polisher unit (Omnilap 2000 SBT Inc) after embeded in liquid unsaturated polyester (Epovia, Cray Valley Inc). Then optical microscopic and scanning electron microscopic(SEM) valuations of the implant-abutment interfaces were conducted to assess quality of fit between the mating components. RESULTS: 1) Generally, the geometry of the internal connection system provided for a precision fit of the implant/abutment interface. 2) The most precision fit of the implant/abutment interface was provided in the case of Bicon System which has not screw. 3) The fit of the implant/abutment interface was usually good in the case of ITI, 3I and Avana system and the amount of fit of the implant/abutment interface was similar to each other. 4) The fit of the implant/abutment interface was usually good in the case of Friadent, Astra and Paragon system. The case of Astra system with the inclined contacting surface had the most intimate contact among them. 5) Amount of intimate contact in the abutment screw thread to the mating fixture was larger in assembly with two-piece type which is separated screw from abutment such as Friadent, Astra and Paragon system than in that with one-piece type which is not seperated screw from abutment such as ITI, 3I and Avana system. 6) Amount of contact in the screw and the screw seat of abutment was larger in assembly of Friadent system than in asembly of Astra system or Paragon system. CONCLUSION: Although a little variation in machining accuracy and consistency was noted in the samples, important features of all internal connection systems were the deep, internal implant - abutment connections which provides intimate contact with the implant walls to resist micromovement, resulting in a strong stable interface. From the results of this study, further research of the stress distribution according to the design of internal connection system will be required.
Polyesters ; Torque

A series of poly (lacticacid-co-glycolicacid)-poly(ethylene glycol) (PLGA-PEG, PELGA) block copolymers and poly (ethylene glycol)-poly (lacticacid-co-glycolicacid)-poly (ethylene-glycol) (PELGE) was synthesized by ring-opening polymerization. PELGA nanoparticles and PELGE nanoparticles were prepared using the emulsion-solvent evaporation technique (O/W). To study the behavior and mechanism of the degradation of PELGA-NP and PELGA-NP, we determined the lactic acids by UV spectrophotometry. The method confirmed that degradation was much faster for polymers with a decrease in the LA content of the polymers or an increase in the PEG content of the polymers.
Biocompatible Materials ; chemistry ; Biodegradation, Environmental ; Drug Carriers ; Drug Delivery Systems ; Humans ; Lactic Acid ; chemical synthesis ; chemistry ; Microspheres ; Nanostructures ; Nanotechnology ; Polyesters ; chemical synthesis ; chemistry ; Polyethylene Glycols ; chemical synthesis ; chemistry ; Polyglactin 910 ; chemistry ; Polyglycolic Acid ; chemical synthesis ; chemistry ; Polymers ; chemical synthesis ; chemistry

Animals ; Biological Availability ; Drug Carriers ; chemistry ; Drug Delivery Systems ; Humans ; Lactic Acid ; chemistry ; pharmacokinetics ; Nanoparticles ; Polyesters ; Polyethylene Glycols ; chemistry ; pharmacokinetics ; Polyglactin 910 ; chemistry ; pharmacokinetics ; Polyglycolic Acid ; chemistry ; pharmacokinetics ; Polymers ; chemistry ; pharmacokinetics