The selection of carbon sources and the biosynthesis of polyhydroxybutyrate(PHB)by the Azotobacter vinelandii N-15 strain using renewable raw materials were investigated.Among the tested substrates(starch,sucrose,mola...The selection of carbon sources and the biosynthesis of polyhydroxybutyrate(PHB)by the Azotobacter vinelandii N-15 strain using renewable raw materials were investigated.Among the tested substrates(starch,sucrose,molasses,bran),molasses as the carbon source yielded the highest PHB production.The maximum polymer yield(26%of dry biomass)was achieved at a molasses concentration of 40 g/L.PHB formation was confirmed via thinlayer chromatography,gas chromatography and Fourier transform infrared spectroscopy.Composite films based on PHB,polylactic acid(PLA),and their blends were fabricated using the solvent casting.The biodegradation of these films was studied with bacteria isolated from plastic-contaminated soil.These bacteria utilized the biopolymers as their sole carbon source,with the biodegradation process lasting three months.Structural and chemical changes in the films were analyzed using FTIR spectroscopy,differential scanning calorimetry,and thermogravimetry.Among the microorganisms used to study the biodegradation of PHB,PLA,and their blends,Streptomyces sp.K2 and Streptomyces sp.K4 exhibited the highest biodegradation efficiency.PHB-containing films demonstrated significant advantages over other biodegradable polymers,as they degrade under aerobic conditions via enzymatic hydrolysis using microbial depolymerases.展开更多
The PHB （polyhydroxybutyrate） films were reported recently as promising materials for tissue involving cultivation of dermoblasts, fibroblasts and connective tissue. In the present work, the authors studied PHB scaf...The PHB （polyhydroxybutyrate） films were reported recently as promising materials for tissue involving cultivation of dermoblasts, fibroblasts and connective tissue. In the present work, the authors studied PHB scaffolds for the cardiac tissue engineering, either in a form of thin membranes or electrospun fiber mats. The results show that cardiac cells of various origins can be successfully grown on PHB substrates, in the both forms： membrane and nanofiber matrix. Functioning of obtained tissue patches was tested by visual observation of contractions and with the aid of optical mapping, i.e., registration of excitation waves with fluorescent markers. The latter one allowed ensuring the fact that cultured cells represented electrophysiological syncytium, and the PHB scaffold showed its full compatibility with the excitability of cardiac cells.展开更多
An extracellular polyhydroxybutyrate（PHB） depolymerase was purified to homogeneity from the culture supernatant of a PHB-degrading bacterium, Pseudomonas mendocina DSWY0601, which was isolated from brewery sewage fo...An extracellular polyhydroxybutyrate（PHB） depolymerase was purified to homogeneity from the culture supernatant of a PHB-degrading bacterium, Pseudomonas mendocina DSWY0601, which was isolated from brewery sewage for the ability to form clear zones on the PHB mineral agar plates. The molecular weight of the purified PHB depolymerase as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis（SDS-PAGE） was ap- proximately 59800 at the optimal temperature and pH value being 50 ℃ and 8.5, respectively. PHB depolymerase was stable in a temperature range of 20--50 ℃ and sensitive to pH value within a pH range of 8.0-9.5. PHB depo- lymerase degraded poly-3-hydroxybutyrate-co-4-hydroxybutyrate（P3/4HB） and poly-3-hydroxybutyrate-co-3- hydroxyvalerate（PHBV） but did not degrade poly（lactic acid）（PLA）, poly（butylene succinate）（PBS） or poly- （caprolactone）（PCL）. PHB depolymerase was sensitive to phenylmethylsulfonyl fluoride（PMSF）, H202 and SDS. The main product after enzymatic degradation of PHB was indentified as 3-hydroxbutyrate monomer（3HB） by mass spectrometric analysis, suggesting that PHB depolymerase acted as an exo-type hydrolase. Analysis ofphaZpm gene reveals that PHB depolymerase is a typical denatured short-chain-length PHA（dPHAscL, PHA=polyhydroxyalkanoate） depolymerase containing catalytic domain, linker and substrate-binding domain.展开更多
The effects of different NaCl concentrations, nitrogen sources, carbon sources, and carbon to nitrogen molar ratios on biomass accumulation and polyhydroxybutyrate （PHB） production were studied in batch cultures of ...The effects of different NaCl concentrations, nitrogen sources, carbon sources, and carbon to nitrogen molar ratios on biomass accumulation and polyhydroxybutyrate （PHB） production were studied in batch cultures of the marine photosynthetic bacterium Rhodovulum sulfidophilum P5 under aerobic-dark conditions. The results show that the accumulation of PHB in strain P5 is a growth-associated process. Strain P5 had maximum biomass and PHB accumulation at 2%-3% NaCl, suggesting that the bacterium can maintain growth and potentially produce PHB at natural seawater salinity. In the nitrogen source test, the maximum biomass accumulation （8.10±0.09 g/L） and PHB production （1.11±0.13 g/L and 14.62%±2.25% of the cell dry weight） were observed when peptone and ammonium chloride were used as the sole nitrogen source. NH^-N was better for PHB production than other nitrogen sources. In the carbon source test, the maximum biomass concentration （7.65±0.05 g/L） was obtained with malic acid as the sole carbon source, whereas the maximum yield of PHB （5.03±0.18 g/L and 66.93%± 1.69% of the cell dry weight） was obtained with sodium pyruvate as the sole carbon source. In the carbon to nitrogen ratios test, sodium pyruvate and ammonium chloride were selected as the carbon and nitrogen sources, respectively. The best carbon to nitrogen molar ratio for biomass accumulation （8.77±0.58 g/L） and PHB production （6.07±0.25 g/L and 69.25%±2.05% of the cell dry weight） was 25. The results provide valuable data on the production of PHB by R. sulfidophilum P5 and further studies are on-going for best cell growth and PHB yield.展开更多
Polyhydroxyalkanoates（PHAs） are aliphatic polyesters accumulated intracellularly by both Gram-negative and Gram-positive bacteria. However, compared to the PHAs of Gramnegative bacteria, few endotoxins（lipopolysacc...Polyhydroxyalkanoates（PHAs） are aliphatic polyesters accumulated intracellularly by both Gram-negative and Gram-positive bacteria. However, compared to the PHAs of Gramnegative bacteria, few endotoxins（lipopolysaccharides, LPS）, which would be co-purified with PHAs and cause immunogenic reactions, are found in the PHAs produced by Gram-positive bacteria. A thermophilic Gram-positive bacterium K5, which exhibited good growth and polyhydroxybutyrate（PHB）-accumulating ability, has been isolated and characterized from a biotrickling filter designed for the removal of NOx from flue gas in a coal-fired power plant in China. Based on the biochemical characterization and 16 S rRNA gene sequence（Genbank accession no. JX437933）, the strain K5 has been identified as Bacillus shackletonii, which has rarely been reported in the literature, and this report is the first time that B. shackletonii has been found to accumulate PHB. The strain K5 was able to utilize glucose as carbon source to synthesize PHB at a broad range of temperatures（from 35 to 50 °C）, and the ideal temperature was 45 °C. The strain K5 could effectively yield PHB of up to 69.9% of its cell dry weight（CDW）（2.28 g/L） in flask experiments employing glucose as carbon source at 45 °C, followed by 56.8% and 52.3% of its CDW when using sodium succinate and glycerol as carbon source, respectively. For batch cultivation, the strain K5 was able to produce PHB of up to 72.6% of its cell dry weight（9.76 g/L） employing glucose as carbon source at 45 °C and pH 7.0.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
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
基金financial support of this paper by the Ministry of Education and Science of Ukraine under grant(Biotherm/0124U000789).
文摘The selection of carbon sources and the biosynthesis of polyhydroxybutyrate(PHB)by the Azotobacter vinelandii N-15 strain using renewable raw materials were investigated.Among the tested substrates(starch,sucrose,molasses,bran),molasses as the carbon source yielded the highest PHB production.The maximum polymer yield(26%of dry biomass)was achieved at a molasses concentration of 40 g/L.PHB formation was confirmed via thinlayer chromatography,gas chromatography and Fourier transform infrared spectroscopy.Composite films based on PHB,polylactic acid(PLA),and their blends were fabricated using the solvent casting.The biodegradation of these films was studied with bacteria isolated from plastic-contaminated soil.These bacteria utilized the biopolymers as their sole carbon source,with the biodegradation process lasting three months.Structural and chemical changes in the films were analyzed using FTIR spectroscopy,differential scanning calorimetry,and thermogravimetry.Among the microorganisms used to study the biodegradation of PHB,PLA,and their blends,Streptomyces sp.K2 and Streptomyces sp.K4 exhibited the highest biodegradation efficiency.PHB-containing films demonstrated significant advantages over other biodegradable polymers,as they degrade under aerobic conditions via enzymatic hydrolysis using microbial depolymerases.
文摘The PHB （polyhydroxybutyrate） films were reported recently as promising materials for tissue involving cultivation of dermoblasts, fibroblasts and connective tissue. In the present work, the authors studied PHB scaffolds for the cardiac tissue engineering, either in a form of thin membranes or electrospun fiber mats. The results show that cardiac cells of various origins can be successfully grown on PHB substrates, in the both forms： membrane and nanofiber matrix. Functioning of obtained tissue patches was tested by visual observation of contractions and with the aid of optical mapping, i.e., registration of excitation waves with fluorescent markers. The latter one allowed ensuring the fact that cultured cells represented electrophysiological syncytium, and the PHB scaffold showed its full compatibility with the excitability of cardiac cells.
基金Supported by the National Natural Science Foundation of China (Nos.31100046,31100099)
文摘An extracellular polyhydroxybutyrate（PHB） depolymerase was purified to homogeneity from the culture supernatant of a PHB-degrading bacterium, Pseudomonas mendocina DSWY0601, which was isolated from brewery sewage for the ability to form clear zones on the PHB mineral agar plates. The molecular weight of the purified PHB depolymerase as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis（SDS-PAGE） was ap- proximately 59800 at the optimal temperature and pH value being 50 ℃ and 8.5, respectively. PHB depolymerase was stable in a temperature range of 20--50 ℃ and sensitive to pH value within a pH range of 8.0-9.5. PHB depo- lymerase degraded poly-3-hydroxybutyrate-co-4-hydroxybutyrate（P3/4HB） and poly-3-hydroxybutyrate-co-3- hydroxyvalerate（PHBV） but did not degrade poly（lactic acid）（PLA）, poly（butylene succinate）（PBS） or poly- （caprolactone）（PCL）. PHB depolymerase was sensitive to phenylmethylsulfonyl fluoride（PMSF）, H202 and SDS. The main product after enzymatic degradation of PHB was indentified as 3-hydroxbutyrate monomer（3HB） by mass spectrometric analysis, suggesting that PHB depolymerase acted as an exo-type hydrolase. Analysis ofphaZpm gene reveals that PHB depolymerase is a typical denatured short-chain-length PHA（dPHAscL, PHA=polyhydroxyalkanoate） depolymerase containing catalytic domain, linker and substrate-binding domain.
基金Supported by the National Natural Science Foundation of China (Nos.30830015, 40806063)the Key Natural Science Foundation of Tianjin,China (No. 12JC2DJC22200)+2 种基金the Natural Science Foundation of Guangxi,China (No. 1000050096)the Foundation of Tianjin Key Laboratory of Marine Resources and Chemistry (Tianjin University of Science & Technology) (No. 200913)the Introduced Talents Scientific Research Initiating Foundation of Tianjin University of Science and Technology (No.20100410)
文摘The effects of different NaCl concentrations, nitrogen sources, carbon sources, and carbon to nitrogen molar ratios on biomass accumulation and polyhydroxybutyrate （PHB） production were studied in batch cultures of the marine photosynthetic bacterium Rhodovulum sulfidophilum P5 under aerobic-dark conditions. The results show that the accumulation of PHB in strain P5 is a growth-associated process. Strain P5 had maximum biomass and PHB accumulation at 2%-3% NaCl, suggesting that the bacterium can maintain growth and potentially produce PHB at natural seawater salinity. In the nitrogen source test, the maximum biomass accumulation （8.10±0.09 g/L） and PHB production （1.11±0.13 g/L and 14.62%±2.25% of the cell dry weight） were observed when peptone and ammonium chloride were used as the sole nitrogen source. NH^-N was better for PHB production than other nitrogen sources. In the carbon source test, the maximum biomass concentration （7.65±0.05 g/L） was obtained with malic acid as the sole carbon source, whereas the maximum yield of PHB （5.03±0.18 g/L and 66.93%± 1.69% of the cell dry weight） was obtained with sodium pyruvate as the sole carbon source. In the carbon to nitrogen ratios test, sodium pyruvate and ammonium chloride were selected as the carbon and nitrogen sources, respectively. The best carbon to nitrogen molar ratio for biomass accumulation （8.77±0.58 g/L） and PHB production （6.07±0.25 g/L and 69.25%±2.05% of the cell dry weight） was 25. The results provide valuable data on the production of PHB by R. sulfidophilum P5 and further studies are on-going for best cell growth and PHB yield.
基金supported by the National Natural Science Foundation of China (No. 51378217, U1360101)the research Project of Guangdong Provincial Department of Science and Technology Department (No. 2012A010800006)the Guangdong Natural Science and Foundation (No. S2012020010887)
文摘Polyhydroxyalkanoates（PHAs） are aliphatic polyesters accumulated intracellularly by both Gram-negative and Gram-positive bacteria. However, compared to the PHAs of Gramnegative bacteria, few endotoxins（lipopolysaccharides, LPS）, which would be co-purified with PHAs and cause immunogenic reactions, are found in the PHAs produced by Gram-positive bacteria. A thermophilic Gram-positive bacterium K5, which exhibited good growth and polyhydroxybutyrate（PHB）-accumulating ability, has been isolated and characterized from a biotrickling filter designed for the removal of NOx from flue gas in a coal-fired power plant in China. Based on the biochemical characterization and 16 S rRNA gene sequence（Genbank accession no. JX437933）, the strain K5 has been identified as Bacillus shackletonii, which has rarely been reported in the literature, and this report is the first time that B. shackletonii has been found to accumulate PHB. The strain K5 was able to utilize glucose as carbon source to synthesize PHB at a broad range of temperatures（from 35 to 50 °C）, and the ideal temperature was 45 °C. The strain K5 could effectively yield PHB of up to 69.9% of its cell dry weight（CDW）（2.28 g/L） in flask experiments employing glucose as carbon source at 45 °C, followed by 56.8% and 52.3% of its CDW when using sodium succinate and glycerol as carbon source, respectively. For batch cultivation, the strain K5 was able to produce PHB of up to 72.6% of its cell dry weight（9.76 g/L） employing glucose as carbon source at 45 °C and pH 7.0.
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.
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.
