Polyhydroxybutyrate (PHB) is known to be temporarily stored as carbon and energy storage by microorganisms in activated sludge.On the other hand,PHB is a thermoplastic with remarkable characteristics of biodegradabili...Polyhydroxybutyrate (PHB) is known to be temporarily stored as carbon and energy storage by microorganisms in activated sludge.On the other hand,PHB is a thermoplastic with remarkable characteristics of biodegradability.The possibility of using activated sludge for the production of PHB was investigated in this paper,focusing on increasing the PHB content of activated sludge.The experimental results show that the activated sludge without acclimatization especially with acetate as excessive carbon resource,accumulated PHB of 11.85% MLSS(Mixed Liquor Sespended Solid) in the anaerobic process;12.95% in the aerobic process;18.49% in the aerobic-anaerobic process.The structrue of the PHB product was determined by 1 HNMR.展开更多
On polyhydroxybutyrate banded spherulites, concentric rings were observed between cross polarizers or without polarizers. The rings used to be considered as cracks. In this paper, we provide evidences to distinguish t...On polyhydroxybutyrate banded spherulites, concentric rings were observed between cross polarizers or without polarizers. The rings used to be considered as cracks. In this paper, we provide evidences to distinguish the concentric rings from cracks observed on PHB spherulites. Furthermore, atomic force microscopy confirmed that these concentric rings with varying spacing were growth terraces rather than cracks. The height of the terraces reached up to several hundred nanometers. It was observed that the external terraces were higher than the internal terraces, which was proposed to result from layer by layer growth. This is the first report on the new microscopic feature of polyhydroxybutyrate spherulites. Spherulites with birefringent bands, wavy fluctuation of height were also observed.展开更多
Many bacteria have been found to synthesize a family of polyesters termed polyhydroxyalkanoate, abbreviated as PHA. Some interesting physical properties of PHAs such as piezoelectricity, non-linear optical activity, b...Many bacteria have been found to synthesize a family of polyesters termed polyhydroxyalkanoate, abbreviated as PHA. Some interesting physical properties of PHAs such as piezoelectricity, non-linear optical activity, biocompatibility and biodegradability offer promising applications in areas such as degradable packaging, tissue engineering and drug delivery. Over 90 PHAs with various structure variations have been reported and the number is still increasing. The mechanical property of PHAs changes from brittle to flexible to elastic, depending on the side-chainlength of PHA. Many attempts have been made to produce PHAs as biodegradable plastics using various microorganisms obtained from screening natural environments, genetic engineering and mutation. Due to the high production cost, PHAs still can not compete with the nondegradable plastics, such as polyethylene and polypropylene. Various processes have been developed using low cost raw materials for fermentation and an inorganic extraction process for PHA purification. However, a super PHA production strain may play the most critical role for any large-scale PHA production. Our recent study showed that PHA synthesis is a common phenomenon among bacteria inhabiting various locations, especially oil-contaminated soils. This is very important for finding a suitable bacterial strain for PHA production. In fact, PHA production strains capable of rapid growth and rapid PHA synthesis on cheap molasses substrate have been found on molasses contaminated soils. A combination of novel properties and lower cost will allow easier commercialization of PHA for many applications.展开更多
The management and recycling of plastic waste is a challenging global issue.Polyethylene terephthalate(PET),one of the most widely used synthetic plastics,can be hydrolyzed by a series of enzymes.However,upcycling the...The management and recycling of plastic waste is a challenging global issue.Polyethylene terephthalate(PET),one of the most widely used synthetic plastics,can be hydrolyzed by a series of enzymes.However,upcycling the resulting monomers is also a problem.In this study,we designed a co-cultivation system,in which PET degradation was coupled with polyhydroxybutyrate(PHB)production.First,PETase from Ideonalla sakaiensis was expressed in Yarrowia lipolytica Po1f with a signal peptide from lipase.The engineered PETase-producing Y.lipolytica was confirmed to hydrolyze bis(2-hydroxyethyl)terephthalate(BHET)and PET powder into the monomers terephthalate(TPA)and ethylene glycol(EG).Simultaneously,a TPA-degrading Pseudomonas stutzeri strain isolated from PET waste was transformed with a recombinant plasmid containing the phb CAB operon from Ralstonia eutropha,which encodes enzymes for the biosynthesis of PHB.The two co-cultivated engineered microbes could directly hydrolyze BHET to produce the bioplastic PHB in one fermentation step.During this process,5.16 g/L BHET was hydrolyzed in 12 h,and 3.66 wt%PHB(3.54 g/L cell dry weight)accumulated in 54 h.A total of 0.31g/L TPA was produced from the hydrolyzation of PET in 228 h.Although PHB could not be synthesized directly from PET because of the low hydrolyzing efficiency of PETase,this study provides a new strategy for the biodegradation and upcycling of PET waste by artificial microflora.展开更多
Date palm pit(DPP)-filled poly(-hydroxybutyrate)(PHB)composites were prepared,evaluated,and characterized to determine their thermal insulation ability.Thermal conductivity values ranged between 0.086 and 0.100 W/(m&#...Date palm pit(DPP)-filled poly(-hydroxybutyrate)(PHB)composites were prepared,evaluated,and characterized to determine their thermal insulation ability.Thermal conductivity values ranged between 0.086 and 0.100 W/(m·K).At a maximum filler concentration(50%(w)),the specific heat capacity and thermal diffusivity were 1183 J/(kg·K)and 0.0689 mm^(2)/s,respec-tively.The DPP increased the thermal stability,and the highest compressive strength obtained was 80 MPa at 30%filler content.The PHB-DPP composites exhibited promising water absorption(less than 6%)and tensile strength(6-14 MPa).Date-pit-based PHB composites could be used in sustainable building engineering and cleaner production.展开更多
文摘Polyhydroxybutyrate (PHB) is known to be temporarily stored as carbon and energy storage by microorganisms in activated sludge.On the other hand,PHB is a thermoplastic with remarkable characteristics of biodegradability.The possibility of using activated sludge for the production of PHB was investigated in this paper,focusing on increasing the PHB content of activated sludge.The experimental results show that the activated sludge without acclimatization especially with acetate as excessive carbon resource,accumulated PHB of 11.85% MLSS(Mixed Liquor Sespended Solid) in the anaerobic process;12.95% in the aerobic process;18.49% in the aerobic-anaerobic process.The structrue of the PHB product was determined by 1 HNMR.
文摘On polyhydroxybutyrate banded spherulites, concentric rings were observed between cross polarizers or without polarizers. The rings used to be considered as cracks. In this paper, we provide evidences to distinguish the concentric rings from cracks observed on PHB spherulites. Furthermore, atomic force microscopy confirmed that these concentric rings with varying spacing were growth terraces rather than cracks. The height of the terraces reached up to several hundred nanometers. It was observed that the external terraces were higher than the internal terraces, which was proposed to result from layer by layer growth. This is the first report on the new microscopic feature of polyhydroxybutyrate spherulites. Spherulites with birefringent bands, wavy fluctuation of height were also observed.
基金Tsinghua University 985 Project Fund and The State 95 Key Research and Development Fund and Hong Kong Polytechnic University contributed to this project.
文摘Many bacteria have been found to synthesize a family of polyesters termed polyhydroxyalkanoate, abbreviated as PHA. Some interesting physical properties of PHAs such as piezoelectricity, non-linear optical activity, biocompatibility and biodegradability offer promising applications in areas such as degradable packaging, tissue engineering and drug delivery. Over 90 PHAs with various structure variations have been reported and the number is still increasing. The mechanical property of PHAs changes from brittle to flexible to elastic, depending on the side-chainlength of PHA. Many attempts have been made to produce PHAs as biodegradable plastics using various microorganisms obtained from screening natural environments, genetic engineering and mutation. Due to the high production cost, PHAs still can not compete with the nondegradable plastics, such as polyethylene and polypropylene. Various processes have been developed using low cost raw materials for fermentation and an inorganic extraction process for PHA purification. However, a super PHA production strain may play the most critical role for any large-scale PHA production. Our recent study showed that PHA synthesis is a common phenomenon among bacteria inhabiting various locations, especially oil-contaminated soils. This is very important for finding a suitable bacterial strain for PHA production. In fact, PHA production strains capable of rapid growth and rapid PHA synthesis on cheap molasses substrate have been found on molasses contaminated soils. A combination of novel properties and lower cost will allow easier commercialization of PHA for many applications.
基金funding from the National Natural Science Foundation of China(grant numbers:Institute of Microbiology,Chi-nese Academy of Sciences:31961133016Beijing Institute of Technol-ogy:31961133015Shandong University:31961133014)and the Na-tional Key Research and Development Program of China(grant num-ber:2019YFA0706900)and was supported by European Union’s Hori-zon 2020 research and innovation programme under grant agreement No.870292(BIOICEP).
文摘The management and recycling of plastic waste is a challenging global issue.Polyethylene terephthalate(PET),one of the most widely used synthetic plastics,can be hydrolyzed by a series of enzymes.However,upcycling the resulting monomers is also a problem.In this study,we designed a co-cultivation system,in which PET degradation was coupled with polyhydroxybutyrate(PHB)production.First,PETase from Ideonalla sakaiensis was expressed in Yarrowia lipolytica Po1f with a signal peptide from lipase.The engineered PETase-producing Y.lipolytica was confirmed to hydrolyze bis(2-hydroxyethyl)terephthalate(BHET)and PET powder into the monomers terephthalate(TPA)and ethylene glycol(EG).Simultaneously,a TPA-degrading Pseudomonas stutzeri strain isolated from PET waste was transformed with a recombinant plasmid containing the phb CAB operon from Ralstonia eutropha,which encodes enzymes for the biosynthesis of PHB.The two co-cultivated engineered microbes could directly hydrolyze BHET to produce the bioplastic PHB in one fermentation step.During this process,5.16 g/L BHET was hydrolyzed in 12 h,and 3.66 wt%PHB(3.54 g/L cell dry weight)accumulated in 54 h.A total of 0.31g/L TPA was produced from the hydrolyzation of PET in 228 h.Although PHB could not be synthesized directly from PET because of the low hydrolyzing efficiency of PETase,this study provides a new strategy for the biodegradation and upcycling of PET waste by artificial microflora.
基金financially supported by UAE University (SURE+2022 Grant#G00003848).
文摘Date palm pit(DPP)-filled poly(-hydroxybutyrate)(PHB)composites were prepared,evaluated,and characterized to determine their thermal insulation ability.Thermal conductivity values ranged between 0.086 and 0.100 W/(m·K).At a maximum filler concentration(50%(w)),the specific heat capacity and thermal diffusivity were 1183 J/(kg·K)and 0.0689 mm^(2)/s,respec-tively.The DPP increased the thermal stability,and the highest compressive strength obtained was 80 MPa at 30%filler content.The PHB-DPP composites exhibited promising water absorption(less than 6%)and tensile strength(6-14 MPa).Date-pit-based PHB composites could be used in sustainable building engineering and cleaner production.
