The degradation of plastics and the production of polyhydroxyalkanoates (PHA) / 生物工程学报

In recent years, the petroleum-based plastic pollution problem has been causing global attention. The idea of "degradation and up-cycling of plastics" was proposed for solving the environmental pollution caused by non-degradable plastics. Following this idea, plastics would be firstly degraded and then reconstructed. Polyhydroxyalkanoates (PHA) can be produced from the degraded plastic monomers as a choice to recycle among various plastics. PHA, a family of biopolyesters synthesized by many microbes, have attracted great interest in industrial, agricultural and medical sectors due to its biodegradability, biocompatibility, thermoplasticity and carbon neutrality. Moreover, the regulations on PHA monomer compositions, processing technology, and modification methods may further improve the material properties, making PHA a promising alternative to traditional plastics. Furthermore, the application of the "next-generation industrial biotechnology (NGIB)" utilizing extremophiles for PHA production is expected to enhance the PHA market competitiveness, promoting this environmentally friendly bio-based material to partially replace petroleum-based products, and achieve sustainable development with carbon-neutrality. This review summarizes the basic material properties, plastic upcycling via PHA biosynthesis, processing and modification methods of PHA, and biosynthesis of novel PHA.

Molecular Characterization, Optimization and Production of PHA by Indigenous Bacteria Using Alternative Nutrient Sources as Substrate

Polyhydroxyalkanoates (PHA) are renewable, biodegradable biopolymer intracellularly accumulated by wide array of microorganisms as carbon reserve. This study investigates the influence of various cultural conditions on PHA production by a recently isolated local species under submerged fermentation. Six PHA producing strains were identified by 16S rDNA gene sequencing and strain Priestia flexa OWO1 showed satisfactory PHA productivity. The effects of production parameters were investigated and extraction of PHA was carried out using sodium hypochlorite method and maximum amount was detected after 72h. Maximum PHA production was obtained at incubation period of 48h, pH of 7.0 and temperature of 30oC. Amongst the hydrolysate of agro waste used, brewers spent grain (BSG) gave maximum yield of 3.01g/L while beans bran powder gave the highest PHA yields of 3.9 g/L amongst the organic nitrogen sources tested. Analysis of the crude PHA by Fourier Transform Infrared Spectroscopy (FT-IR) showed the presence of methyl, methylene as well as carbonyl functional groups. PHA production was higher after optimizing the production conditions as compared to basal medium therefore the utilization of these cheap renewable resources as alternative substrates for production of PHA make the process cost effective and sustainable.

Aislamiento y caracterización de bacterias productoras de biopolimeros a partir de efluentes industriales / Isolated and characterization of biopolymer producing bacteria from industrial effluents

RESUMEN Se realizó una caracterización físico-química de los efluentes procedentes de industrias del sector educación, metalmecánico, lácteos y confitería de la ciudad de Manizales, Caldas; posteriormente se obtuvieron aislamientos, en medios diferenciales suplementados, de bacterias con potencial para la producción de biopolímeros a los cuales se les aplicó pruebas para la caracterización morfológica, bioquímica y molecular. Los parámetros físico químicos obtenidos de los efluentes industriales demuestran diferencias entre ellos, ya que cada industria genera diferentes residuos aportando una determinada contaminación al efluente, se obtuvieron 73 aislamientos productores de exopolisacáridos (EPS) y 101 productores de polihidroxialcanoatos (PHA), con características morfológicas y bioquímicas variables. El estudio muestra que los efluentes industriales son una gran fuente de bacterias de interés para la producción de diversos polímeros microbianos; principalmente aquellos que producen polímeros tipo biopoliésteres intracelulares como PHA, debido a su variabilidad físico-química y nutricional permitiendo que los microorganismos se adapten a diversas características medioambientales y de composición.

ABSTRACT A physical-chemical characterization of effluents from industries in the education, metal-mechanic, dairy and confectionery sectors of the city of Manizales, Caldas; Later isolates were obtained, in differential media supplemented, from bacteria with potential for the production of biopolymers to which they were applied tests for morphological, biochemical and molecular characterization. The physical chemical parameters obtained from the industrial effluents show a difference between them, since each industry generates different waste contributing a certain contamination to the effluent, 73 isolates producing exopolysaccharides (EPS) and 101 producers of polyhydroxyalkanoates (PHA) were obtained, with morphological characteristics and variable biochemistry. The study shows that industrial effluents are a great source of bacteria of interest for the production of various microbial polymers; mainly those that produce polymers like intracellular biopolyesters such as PHA, due to their physical-chemical and nutritional variability allowing the microorganisms to adapt to diverse environmental and compositional characteristics.

Dual application of black soldier fly (Hermetia illucens): Protein-rich animal feed and biological extraction agent for polyhydroxybutyrate

Aims@#The primary aim of the present study is to evaluate the effect of rearing substrates on the nutritional content of black soldier fly larvae (BSFL) by incorporating Cupriavidus necator cells containing intracellular polyhydroxybutyrate (PHB) in BSFL diet to further increase the protein content and simultaneously to biologically extract the polymer by utilizing the digestive system of BSFL. The potential application of BSFL as a biological PHB extraction agent was determined.@*Methodology and results@#Two feeding strategies consists of a mixture of protein (P) to carbohydrate (C) with a ratio of P50:C50 food waste (control feeding) and feed with bacterial cells (modified feeding). A comparison on the proximate analysis between this research and two commercially available products were conducted. Feeding BSFL with P50:C50 food waste revealed the highest crude protein content of 81.3 ± 0.2%. Additional bacteria cells in the BSFL diet, however, showed a negligible decrease in crude protein content of 0.67% as compared to the control feeding. Howbeit, this results comparably higher in contrast to the commercial products, with increment of crude protein content by 12.1% and 40.8%, respectively.@*Conclusion, significance and impact of study@#Two desirable products were obtained from the feeding with cells: (1) high protein content of BSFL and (2) biologically extracted polymer. This is the first study to demonstrate the utilization of BSFL as a biological extraction agent to partially extract biopolymer and increase the protein content by feeding with cells.

Thirty years of metabolic engineering for biosynthesis of polyhydroxyalkanoates / 生物工程学报

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.

Effect of short-chain thioesterase deficiency on P(3HB-co-LA) biosynthesis in Escherichia coli / 生物工程学报

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.

A review on polyhydroxyalkanoates synthesis in activated sludge system: the effects of dissolved organic compounds by using anaerobic fermentation liquid from waste activated sludge / 生物工程学报

Polyhydroxyalkanoates (PHA) synthesis by activated sludge using volatile fatty acids (VFAs) in fermentation liquid of excess sludge as carbon source is a hotspot in the field of environmental biotechnology. However, there is no unified conclusion on the effects of non-VFAs, mainly dissolved organic matter (DOM), on PHA production. Thus, this critical review mainly introduces the main characteristics and common analysis methods of DOM in anaerobic fermentation liquid. The effects of DOM on PHA production are analyzed from the aspects of microbiology, metabolic regulation and sludge properties. The results of different studies showed that high concentration of DOM is bad for PHA production, but an appropriate amount of DOM is conducive to the stability of sludge properties, reducing the final PHA purification cost. Finally, suitable strategies were proposed to regulate the PHA synthesis by activated sludge with DOM for PHA production by anaerobic fermentation liquid.

Effect of carbon/nitrogen ratio on polyhydroxyalkanoates production by Bacillus species under submerged fermentation

Aim: To analyze the effect of carbon/nitrogen (C/N) ratio on polyhydroxyalkanoates (PHAs) production by Bacillus species under submerged fermentation process.Methodology: Preserved polyhydroxyalkanoates producing Bacillus sp. C1 (2013) (KF626477) was revived and growth parameters were optimized by one factor at a time approach. The effect of C/N ratio and the influence of time period on polyhydroxyalkanoates production through submerged fermentation process was evaluated under optimized condition. Primary structural and morphological characterization of extracted polyhydroxyalkanoates was carried out by Fourier Transform Infra-Red Spectroscopy and Field Emission-Scanning Electron Microscopy. Results: Bacillus sp. C1 (2013) produced higher cell biomass in mineral salt medium at pH 9.0, temperature 37oC, dextrose (2%) and ammonium sulphate (1%) as carbon and nitrogen source with 15% inoculum size. Under optimized condition, higher polyhydroxyalkanoates production of 1.09 g l-1 (49.2%) was obtained at 48 hrs with 2: 0.4 C/N ratio. However, in our previous study 0.909 gl-1 of PHAs was produced by the bacteria at 6:1 carbon to nitrogen ratio. Fourier Transform Infra-Red Spectroscopic analysis showed high intense absorption bands at 1720.18 cm−1 resembled to ester carbonyl functional group of PHB, which is the most common homopolymer of PHAs. Surface morphology of poly-beta-hydroxybutyrate film was rough and fairly regular as revealed from Field Emission-Scanning Electron Microscopic imaging. Interpretation: Poly-beta-hydroxybutyrate production by the bacteria increased under higher degrees of nitrogen deficient condition. Thus, optimized C/N ratio can improve the cost affordability of poly-beta-hydroxybutyrate production, however, further research in contrast to different bacteria is highly essential in this regard.

Research progress in polyhydroxyalkanoates (PHA) and their blend fibers / 生物工程学报

Polyhydroxyalkanoate (PHA) is a representative biodegradable polymer with more than 150 varieties and various properties. This article reviews the research status and potential applications of PHA, and introduces the properties of four-generation commercial PHA and its research progress in blend fibers with other biodegradable materials.

Bioconversion of sugarcane molasses to poly(3-hydroxybutyrate-co-3- hydroxyvalerate) by endophytic Bacillus cereus RCL 02

Sugarcane molasses, the by-product of sugar industry are rich in nutrients, growth factors and minerals and areefficiently utilized by the microorganisms for growth and production of primary as well as secondary metabolitesof commercial importance. In this communication, we report the utilization of sugarcane molasses as the solesource of carbon for the production of copolymers of polyhydroxyalkanoates (PHAs) with improved materialproperties. The endophytic bacterium Bacillus cereus RCL 02 (MCC 3436) produced 7.8 g/L of PHA whengrown in MS medium with 4% (w/v) sugarcane molasses under batch cultivation. Proton nuclear magneticresonance (1H NMR) analysis revealed that the copolymer so produced contain 12.4 mol% 3-hydroxyvalerate(3HV) along with 87.6 mol% 3-hydroxybutyrate (3HB). The copolyester, P(3HB-co-12.4 mol%-3HV)has been isolated and purified following standard solvent extraction method and partially characterized byFourier-transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric (TG) and differential scanningcalorimetric (DSC) analysis. The material and thermal properties of the copolyester so produced indicated itspotential for industrial application.

Evaluation of poly(3-hydroxybutyrate) production by microbiota endogenous to oleaginous plants

Aims@#Microbiota endogenous to oleaginous plants have attracted special attention in recent years for their biotechnological potentials and applications including the production of biodegradable biopolyester poly(3- hydroxybutyrate) [P(3HB)] as an alternative to thermoplastics. The present study is aimed to screen the endophytic bacteria of selected oleaginous plants such as Arachis hypogaea L., Brassica napus L., Brassica nigra L., Helianthus annuus L., Ricinus communis L. and Sesamum indicum L. for the production of P(3HB). @*Methodology and results@#Bacteria endogenous to the oleaginous plants were isolated from surface sterilized healthy tissues following sterilization with 70% ethanol and 0.5% sodium hypochlorite and screened for P(3HB) production in mineral salts medium. Nile blue A staining method was used for detection of intracellular P(3HB), while the accumulated biopolyester was quantified spectrophotometrically following chemical conversion to chrotonic acid by treating with sulfuric acid. Five potent P(3HB) accumulating isolates have been selected and identified as Cellulosimicrobium cellulans AHS 01 (KX458038), Beijerinckia fluminensis AHR 02 (KX458039), Exiguobacterium acetylicum BNL 103 (KX458037), Bacillus toyonensis BNS 102 (KX458036) and Bacillus cereus RCL 02 (KX458035) based on morphological, physio-biochemical and 16S rDNA sequence analysis. These endogenously growing bacterial isolates accumulated intracellular biopolyester accounting 43-62% of their cell dry weight (CDW) when grown in mineral salts medium supplemented with yeast extract. Intracellular accumulation of P(3HB) by these isolates have also been confirmed by FTIR spectral analysis of lyophilized cell mass and 1HNMR spectra of the extracted polymer. @*Conclusion, significance and impact of study@#These findings, first of its kind point to exploration of endogenous bacterial communities of oil-producing plants as a potential bioresource for production of P(3HB) bioplastics in a sustainable manner.

Effect of reducing the activity of respiratory chain on biosynthesis of poly(3-hydroxybutyrate-co-lactate) in Escherichia coli / 生物工程学报

Poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] belongs to the polyhydroxyalkanoates (PHA) family and possesses promising properties including biocompatibility and biodegradability. In this study, we directly synthesized P(3HB-co-LA) with glucose by introducing the β-ketothiolase and acetoacetyl-CoA reductase from Ralstonia eutropha, the engineered propionate CoA transferase from Clostridium propionicum and the engineered polyhydroxyalkanoate synthase from Pseudomonas fluorescens strain 2P24 into Escherichia coli. The polymer content was 83.9% (W/W), and the molar percentage of lactate reached 1.6%. On this basis, in order to accumulate lactate, we reduced the activity of respiratory chain by deleting the ubiX gene, which is involved in the synthesis of coenzyme Q8. Moreover, we removed the dld gene to avoid the conversion of lactate to pyruvate during the fermentation. With these manipulations, the molar percentage of lactate in the polymer was improved to 14.1%, with an 81.7% (W/W) of polymer content. The test results indicated that the strategy of reducing the activity of respiratory chain effectively increased the lactate units in the polymer, and it contributed a new approach to change the content of monomer components in the polymer.

Microbial Synthesis and Characterization of Biodegradable Polyester Copolymers from Burkholderia Cepacia and Cupriavidus Necator Strains Using Crude Glycerol as Substrate

Abstract Polymers are materials of pronounced importance in the modern world, since they are massively present in everyday life, especially in the form of packaging. However, most of these materials are derived from non-renewable sources and their disposal generates large volumes of waste, which is extremely damaging to natural environments. In this context, microbial biopolymers appear as a powerful alternative in the substitution of several applications of synthetic plastics, causing less harm to the environment, as they are biodegradable and produced from renewable sources. In this study, evaluation and characterization of polyhydroxyalkanoates (PHAs) produced by Cupriavidus necator (IPT 026 and IPT 027) and Burkholderia cepacia (IPT 119 and IPT 400), using crude glycerol as substrate, were carried out (crude glycerol 15 g L-1, pH 7.0, 150 rpm, 72h). The substrate chemical composition was determined and all microorganisms tested were able to utilize it to synthesize PHA. C. necator IPT 026 exhibited the highest polymer production (1.52 ± 0.03 g L-1). B. cepacia strains produced low crystallinity PHA. All polyesters synthesized exhibited long chain length polymers with low polydispersity and initial thermal degradation temperatures superior to 300°C. The microorganism strains and the substrate composition highly affected PHAs synthesis, composition and thermochemical characteristics.

Polyhydroxyalkanoate biosynthesis by oxalotrophic bacteria from high Andean soil / Biosíntesis de polihidrxialcanoato por bacterias oxalotróficas de suelos altoandinos / Biossínteses de polihidroxialcanoato por bactérias oxalotróficas de solos andinos

Abstract Oxalate is a highly oxidized organic acid anion used as a carbon and energy source by oxalotrophic bacteria. Oxalogenic plants convert atmospheric CO2 into oxalic acid and oxalic salts. Oxalate-salt formation acts as a carbon sink in terrestrial ecosystems via the oxalate-carbonate pathway (OCP). Oxalotrophic bacteria might be implicated in other carbon-storage processes, including the synthesis of polyhydroxyalkanoates (PHAs). More recently, a variety of bacteria from the Andean region of Colombia in Narino have been reported for their PHA-producing abilities. These species can degrade oxalate and participate in the oxalate-carbonate pathway. The aim of this study was to isolate and characterize oxalotrophic bacteria with the capacity to accumulate PHA biopolymers. Plants of the genus Oxalis were collected and bacteria were isolated from the soil adhering to the roots. The isolated bacterial strains were characterized using biochemical and molecular biological methods. The consumption of oxalate in culture was quantified, and PHA production was monitored in batch fermentation. The polymeric composition was characterized using gas chromatography. Finally, a biosynthetic pathway based on our findings and on those from published sources is proposed. Strains of Bacillus spp. and Serratia sp. were found to metabolize calcium oxalate and synthesize PHA.

Resumen El oxalato es un anión de ácido orgánico altamente oxidado usado como fuente carbono y energía por bacterias oxalotróficas. Las plantas oxalogénicas convierten CO2 atmosférico en ácido oxálico y sales oxálicas. La formación de sales de oxalato actúa como un sumidero de carbono en ecosistemas terrestres via oxalato-carbonato (OCP). Las bacterias oxalotróficas podrían estar implicadas en otros procesos de almacenamiento de carbono, incluyendo la síntesis de polihidroxialcanoatos (PHAs). Recientemente, una variedad de bacterias de la región andina colombiana en Nariño ha sido reportada por su habilidad para producir PHAs. Estas especies pueden degradar oxalato y participar en la vía del oxalato-carbonato. El objetivo de este estudio fue aislar y caracterizar bacterias oxalotróficas con capacidad de acumular biopolímeros PHA. Se colectaron plantas del genero Oxalis y se aislaron bacterias del suelo adheridas a las raíces. Las cepas bacterianas aisladas se caracterizaron usando métodos bioquímicos y de biología molecular. Se cuantificó el consumo de oxalato en cultivo, y se monitoreó la producción de PHA en fermentación por lotes. La composición polimérica se caracterizó usando cromatografía de gases. Finalmente, se propone una via biosintética basada en nuestros hallazgos y en los de otras fuentes publicadas. Se encontró que las cepas de Bacillus spp. y Serratia sp. metabolizan oxalato de calcio y sintetizan PHA.

Resumo O oxalato é um ânion de ácido orgânico altamente oxidado utilizado como fonte de carbono e nergía por bactérias oxalotróficas. As plantas oxalogênicas convertem CO2 atmosférico em ácido oxálico e sais oxálicos. A formação de sais de oxalato atua como um sumidouro de carbono em ecossistemas terrestres via oxalato-carbono (OCP). As bactérias oxalotróficas poderiam estar envolvidas em outros processos de armazenamento de carbono, incluindo a sínteses de polihidroxialcanoatos (PHAs). Recentemente, uma variedade de bactérias da região Andina colombiana no Departamento de Nariño foi reportada devido a sua habilidade para produzir PHAs. Estas espécies podem degradar oxalato e participar na via oxalato-carbono. O objetivo de esse estudo foi isolar e caracterizar bactérias oxalotróficas com capacidade de acumular biopolímeros PHA. Plantas do género Oxalis foram coletadas e se isolaram bactérias do solo aderido a suas raízes. As cepas bacterianas isoladas se caracterizaram utilizando métodos bioquímicos e de biologia molecular. O consumo de oxalato em cultivo foi quantificado, e a produção de PHA foi monitorada em fermentação por lotes. A composição polimérica se caracterizou utilizando Cromatografia de Gases. Finalmente, se propõe uma via biossintética baseada em nossos resultados juntamente com resultados da literatura. Se encontrou que as cepas de Bacillus spp. e Serratia sp. metabolizam oxalato de cálcio e sintetizam PHA.

Application perspectives of polyhydroxyalkanoates / 生物工程学报

Polyhydroxyalkanoates are polyesters of hydroxyalkanoates synthesized by many bacteria and haloarchaea as carbon and energy storage materials. There are more than 150 types of polyhydroxyalkanoate monomers reported, resulting in a variety of Polyhydroxyalkanoates with diverse properties. The material variability, nonlinear optical properties, piezoelectric properties, gas barrier properties, thermoplasticity, biodegradability, and biocompatibility allow polyhydroxyalkanoates to be used for plastic packaging, chiral chemicals generation, medicine, agriculture and bio-energy fields. This review introduces the current applications and future development of polyhydroxyalkanoates.

Exploration and application of polyhydroxyalkanoates and polylactic acid membranes during glaucoma filtering surgery and interlaminar transplantation in rabbits / 中国比较医学杂志

Objective To evaluate the effect of two polymer membranes, polyhydroxyalkanoates(PHA)and polylactic acid(PLA)during glaucoma filtration surgery(GFS),and to evaluate the morphology of membranous PHA after interlamellar implantation. Methods Twenty-eight New Zealand white rabbits were chosen and twenty-four of them were randomly divided into 6 groups(n=4):the PHA-low group,PHA-high group,PLA-low group,PLA-high group,positive control group(MMC group)and blank control group. The rabbits in each group received GFS. The corresponding polymer membranes were implanted under the scleral flap,while the MMC group was treated with 0.2 mg/mL mitomycin C(MMC) for 3 minutes,and the blank control group was treated without extra drugs. The intraocular pressure(IOP)was examined at 0 d,1 d, 3 d, 7 d, 14 d, 28 d and 84 d after GFS. The corneal layers of four rabbits were implanted with PHA membranes and the corneal morphological changes were observed after 84 d. Results The IOP of the PHA-low and PLA-high groups was lower than that of the blank control group at 84 d after GFS(P < 0.05),and was similar with that of the MMC group(P> 0.05). Morphological studies showed that there were no collagenous fibers filling in the duct, and the collagenous fibers around the membranes were generally arranged in parallel. There were no obvious changes in the peripheral collagen structure after implantation of PHA membranes between the corneal layers. Conclusions Application of PHA and PLA membranes during GFS in rabbits may maintain the level of IOP,and the effect is similar with MMC. The mechanism may be achieved through the mechanical blocking of fibrous tissue.

Variation analysis of bacterial polyhydroxyalkanoates production using saturated and unsaturated hydrocarbons

ABSTRACT Polyhydroxyalkanoates (PHA) are efficient, renewable and environment friendly polymeric esters. These polymers are synthesized by a variety of microbes under stress conditions. This study was carried out to check the suitability of waste frying oil in comparison to other oils for economical bioplastic production. Six bacterial strains were isolated and identified as Bacillus cereus (KF270349), Klebsiella pneumoniae (KF270350), Bacillus subtilis (KF270351), Brevibacterium halotolerance (KF270352), Pseudomonas aeruginosa (KF270353), and Stenotrophomonas rhizoposid (KF270354) by ribotyping. All strains were PHA producers so were selected for PHA synthesis using four different carbon sources, i.e., waste frying oil, canola oil, diesel and glucose. Extraction of PHA was carried out using sodium hypochlorite method and maximum amount was detected after 72 h in all cases. P. aeruginosa led to maximum PHA production after 72 h at 37 °C and 100 rpm using waste frying oil that was 53.2% PHA in comparison with glucose 37.8% and cooking oil 34.4%. B. cereus produced 40% PHA using glucose as carbon source which was high when compared against other strains. A significantly lesser amount of PHA was recorded with diesel as a carbon source for all strains. Sharp Infrared peaks around 1740-1750 cm-1 were present in Fourier Transform Infrared spectra that correspond to exact position for PHA. The use of waste oils and production of poly-3hydroxybutyrate-co-3hydroxyvalerate (3HB-co-3HV) by strains used in this study is a good aspect to consider for future prospects as this type of polymer has better properties as compared to PHBs.

From waste to treasure: turning activated sludge into bioplastic poly-3-hydroxybutyrate / 生物工程学报

Large quantity of activated sludge is generated from wastewater treatment but without yet an appropriate deposition. High temperature can lyse the activate sludge so that nitrogen and phosphorus containing nutrients are released. Halomonas CJN was found to grow on the heat lysed activated sludge and glucose for production of bioplastic poly-3-hydroxybutyrate (PHB) in the absence of yeast extract, nitrogen and phosphorus sources as well as trace elements. This reduces the PHB production cost significantly. Furthermore, acetic acid formed from anaerobic fermentation of heat lysed activated sludge can be used to replace glucose for cell growth but not much for PHB production. After construction of an additional PHB synthesis pathway in Halomonas CJN, we can produce PHB entirely from heat lysed activated sludge, reducing production cost of PHB roughly from ¥ 30 000 Yuan/ton to ¥ 20 000 Yuan/ton, thus turning waste activated sludge to valuable raw material resource.

Preface for special issue on bio-based materials (2016) / 生物工程学报

Bio-based materials are new materials or chemicals with renewable biomass as raw materials such as grain, legume, straw, bamboo and wood powder. This class of materials includes bio-based polymer, biobased fiber, glycotechnology products, biobased rubber and plastics produced by biomass thermoplastic processing and basic biobased chemicals, for instance, bio-alcohols, organic acids, alkanes, and alkenes, obtained by bio-synthesis, bio-processing and bio-refinery. Owing to its environmental friendly and resource conservation, bio-based materials are becoming a new dominant industry taking the lead in the world scientific and technological innovation and economic development. An overview of bio-based materials development is reported in this special issue, and the industrial status and research progress of the following aspects, including biobased fiber, polyhydroxyalkanoates, biodegradable mulching film, bio-based polyamide, protein based biomedical materials, bio-based polyurethane, and modification and processing of poly(lactic acid), are introduced.

Progress on polyhydroxyalkanoates (PHA) / 生物工程学报

Microbial polyhydroxyalkanoates (PHA) has developed with more diversity and more advanced manufacturing technology. Diversity has now been reflected by diverse monomers, diverse structures and diverse polymerization modes, giving the concept of "PHAome". In addition, the application of synthetic biology and the development of seawater-based biotechnology reduce the production cost of PHA, making PHA more economically competitive. Some examples of commercialized PHA products are described here. Besides, PHA with high value added applications has been exploited.