Synthesis of PHB nanoparticles from optimized medium utilizing dairy industrial waste using Brevibacterium casei SRKP2: A green chemistry approach

Polyhydroxyalkanoates (PHAs) are natural, biodegradable polymers accumulated by bacteria under nutritional exhausted condition where carbon source is in excess. A gram positive bacterium (designated strain SRKP2) that potentially accumulated polyhydroxybutyrate (PHB) was isolated from dairy industrial waste. From its morphological and physiological properties and nucleotide sequence of its 16S rRNA, it was suggested that strain SRKP2 was similar to Brevibacterium casei. PHAs were synthesized from a medium containing dairy waste, yeast extract and sea water. The synthesized PHAs were characterized by FT-IR as Polyhydroxybutyrate (PHB). Response surface methodology was applied to optimize the production of PHB. From the optimized medium the yield of PHB was found to be 2.940 g/L. Here we report the direct use of dairy waste and sea water as potential sources for the production of PHB. Produced PHB was used to synthesize nanoparticles using solvent displacement technique.     

Identification and Quantification of Polycyclic Aromatic Hydrocarbons in Polyhydroxyalkanoates Produced from Mixed Microbial Cultures and Municipal Organic Wastes at Pilot Scale

Polyhydroxyalkanoates (PHAs) are well-known biodegradable plastics produced by various bacterial strains, whose major drawback is constituted by the high cost of their synthesis. Producing PHAs from mixed microbial cultures and employing organic wastes as a carbon source allows us to both reduce cost and valorize available renewable resources, such as food waste and sewage sludge. However, different types of pollutants, originally contained in organic matrices, could persist into the final product, thus compromising their safety. In this work, the exploitation of municipal wastes for PHA production is evaluated from the environmental and health safety aspect by determining the presence of polycyclic aromatic hydrocarbons (PAHs) in both commercial and waste-based PHA samples. Quantification of PAHs by gas chromatography-mass spectrometry on 24 PHA samples obtained in different conditions showed very low contamination levels, in the range of ppb to a few ppm. Moreover, the contaminant content seems to be dependent on the type of PHA stabilization and extraction, but independent from the type of feedstock. Commercial PHA derived from crops, selected for comparison, showed PAH content comparable to that detected in PHAs derived from organic fraction of municipal solid waste. Although there is no specific regulation on PAH maximum levels in PHAs, detected concentrations were consistently lower than threshold limit values set by regulation and guidelines for similar materials and/or applications. This suggests that the use of organic waste as substrate for PHA production is safe for both the human health and the environment.     

Conversion of food industrial wastes into bioplastics with municipal activated sludge

Plastics have become an integral part of our contemporary life because of many desirable properties including durability and resistance to degradation. However, these non-degradable, petrochemicals-derived plastics accumulate in the environment at a rate of 25 million tons per year. Recently there is an interest in the development of a class of microbially produced bioplastics, e.g., polyhydroxyalkanoates (PHAs) which retain the desired physical and chemical properties of conventional synthetic plastics. Broader usage of biodegradable plastics in packaging and disposable products as a solution to the environmental problem would heavily depend on further reduction of costs and the discovery of novel biodegradable plastics with improved properties. In this paper, the microbial production of PHAs by activated sludge utilizing food industrial wastes is reported. The melting points of the products as well as the co-polymer composition of the products investigated by GC and NMR were compared. By use of activated sludge to convert the carbon source into PHAs not only environment-friendly bioplastics are produce, but also part of the problem of the disposal of municipal activated sludge is solved. The selection of food industrial waste as carbon resource can also further reduce the cost of production of PHAs.     

Sustainable Surfactin Production by Bacillus subtilis Using Crude Glycerol from Different Wastes

Most biosurfactants are obtained using costly culture media and purification processes, which limits their wider industrial use. Sustainability of their production processes can be achieved, in part, by using cheap substrates found among agricultural and food wastes or byproducts. In the present study, crude glycerol, a raw material obtained from several industrial processes, was evaluated as a potential low-cost carbon source to reduce the costs of surfactin production by Bacillus subtilis #309. The culture medium containing soap-derived waste glycerol led to the best surfactin production, reaching about 2.8 g/L. To the best of our knowledge, this is the first report describing surfactin production by B. subtilis using stearin and soap wastes as carbon sources. A complete chemical characterization of surfactin analogs produced from the different waste glycerol samples was performed by liquid chromatography–mass spectrometry (LC-MS) and Fourier transform infrared spectroscopy (FTIR). Furthermore, the surfactin produced in the study exhibited good stability in a wide range of pH, salinity and temperatures, suggesting its potential for several applications in biotechnology.     

Conversion of industrial food wastes by Alcaligenes latus into polyhydroxyalkanoates

Broader usage of biodegradable plastics in packaging and disposable products as a solution to environmental problems would heavily depend on further reduction of costs and the discovery of novel biodegradable plastics with improved properties. As the first step in our pursuit of eventual usage of industrial food wastewater as nutrients for microorganisms to synthesise environmental-friendly bioplastics, we investigated the usage of soya wastes from a soya milk dairy, and malt wastes from a beer brewery plant as the carbon sources for the production of polyhydroxyalkanoates (PHA) by selected strain of microorganism. Bench experiments showed that Alcaligenes latus DSM 1124 used the nutrients from malt and soya wastes to biosynthesise PHAs. The final dried cell mass and specific polymer production of A. latus DSM 1124 were 32g/L and 70% polymer/cells (g/g), 18.42 g/L and 32.57% polymer/cell (g/g), and 28 g/L and 36% polymer/cells (g/g), from malt waste, soya waste, and from sucrose, responctively. These results suggest that many types of food wastes might be used as the carbon source for the production of PHA.     

Preparation of activated carbon for mercury capture from chicken waste and coal

Chicken waste and chicken waste blended samples with selected high sulfur coal were used as raw materials for activated carbon preparation. Raw materials were subjected to the preparation procedures of carbonization in a nitrogen atmosphere and activation in a steam atmosphere. The basic properties of the raw materials, chars and activated carbons were investigated by components analysis, surface porosity and thermogravimetric analysis. Two activated carbon samples were selected for elemental mercury capture tests in a lab-scale drop tube reactor with air flow.

The current results show that chicken waste is not a suitable raw material for activated carbon production due to its higher contents of volatile matter and ash. Coal can be used as a carbon carrier for improving the carbon content of products. A low-cost activated carbon was prepared by a co-process of chicken waste and coal, and examining the high capture efficiency for elemental mercury. It suggests that the coal provides a carbon carrier or trap for some active species, such as chlorine released from the chicken waste. These active species would likely provide or create the adsorptive sites on the surface of activated carbon for elemental mercury.     

Preparation of activated carbon for mercury capture from chicken waste and coal

Chicken waste and chicken waste blended samples with selected high sulfur coal were used as raw materials for activated carbon preparation. Raw materials were subjected to the preparation procedures of carbonization in a nitrogen atmosphere and activation in a steam atmosphere. The basic properties of the raw materials, chars and activated carbons were investigated by components analysis, surface porosity and thermogravimetric analysis. Two activated carbon samples were selected for elemental mercury capture tests in a lab-scale drop tube reactor with air flow.The current results show that chicken waste is not a suitable raw material for activated carbon production due to its higher contents of volatile matter and ash. Coal can be used as a carbon carrier for improving the carbon content of products. A low-cost activated carbon was prepared by a co-process of chicken waste and coal, and examining the high capture efficiency for elemental mercury. It suggests that the coal provides a carbon carrier or trap for some active species, such as chlorine released from the chicken waste. These active species would likely provide or create the adsorptive sites on the surface of activated carbon for elemental mercury.     

Production of Polyhydroxyalkanoates in Unsterilized Hyper-Saline Medium by Halophiles Using Waste Silkworm Excrement as Carbon Source

The chlorophyll ethanol-extracted silkworm excrement was hardly biologically reused or fermented by most microorganisms. However, partial extremely environmental halophiles were reported to be able to utilize a variety of inexpensive carbon sources to accumulate polyhydroxyalkanoates. In this study, by using the nile red staining and gas chromatography assays, two endogenous haloarchaea strains: Haloarcula hispanica A85 and Natrinema altunense A112 of silkworm excrement were shown to accumulate poly(3-hydroxybutyrate) up to 0.23 g/L and 0.08 g/L, respectively, when using the silkworm excrement as the sole carbon source. The PHA production of two haloarchaea showed no significant decreases in the silkworm excrement medium without being sterilized compared to that of the sterilized medium. Meanwhile, the CFU experiments revealed that there were more than 60% target PHAs producing haloarchaea cells at the time of the highest PHAs production, and the addition of 0.5% glucose into the open fermentation medium can largely increase both the ratio of target haloarchaea cells (to nearly 100%) and the production of PHAs. In conclusion, our study demonstrated the feasibility of using endogenous haloarchaea to utilize waste silkworm excrement, effectively. The introduce of halophiles could provide a potential way for open fermentation to further lower the cost of the production of PHAs.     

Application of Thermal Analysis to the Study of Some Waste Agricultural Products for the Preparation of Active Carbons

TG, DTG and DTA methods were used for the investigation of some waste agricultural products, such as grape seeds, walnut shells, plum and peach stones, which can serve as raw materials for the production of active carbons. It was demonstrated that thermo analytical methods are appropriate to study the thermal characteristics of the above wastes and the data obtained can be applied to the technological processes of active carbon preparation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Oil Accumulation via Heterotrophic/Mixotrophic <Emphasis Type="Italic">Chlorella protothecoides</Emphasis>

Microalgal oil is a potential energy source because it can be easily converted to fatty acid methyl ester or hydrocarbon type of diesel, and it is produced with relatively higher productivity compared with oil from plants and animals. Heterotrophic growth of microalgae is superior due to its high final product concentration; however, the cost of the raw materials is unacceptable if sugar is utilized as the carbon source. The aim of this study is to optimize the lipid accumulation of Chlorella protothecoides by using carbon sources other than glucose in heterotrophic and mixotrophic cultures. Different factors such as different carbon sources, carbon to nitrogen ratio, initial pH level, salinity, and rotational speed are studied in affecting the cell growth and the oil accumulation. Our experiments revealed that the heterotrophic and mixotrophic cultures of C. protothecoides grew better than autotrophic cultures. C. protothecoides can grow on glycerol or acetate, as well as on glucose. Several stress factors were confirmed or discovered to significantly increase the lipid content of microalgae cells. The replacement of glycerol and acetate as carbon sources for microalgae cultivations provides potential for waste utilization: glycerol from biodiesel industry and acetate from biohydrogen production.     

Production of anode matrices from renewable vegetable raw materials, including agricultural waste

Carbon modifications (anode matrices) were produced from renewable vegetable raw materials, agricultural crop waste, by pyrolysis in a quartz reactor without access of oxygen at 900°C, as well as by mechanical synthesis, and their characteristics were examined.     

Adsorbents from Waste materials

The possibility of using pyrolyzed wastes produced in already working incineration plants, as adsorbents for waste water treatment, was studied. Showing very poor adsorption properties, they were improved by steam activation technique used in the conventional activated carbon manufacturing. It is concluded that various organic waste materials can be converted to carbonaceous final products with a character similar to activated carbon. Their adsorption properties and pore size distribution are determined by the structure of the starting material. Although most of these samples have a low specific surface area, their pore volume is not negligible in the meso-and micropore range. Adsorption tests with model waste waters confirmed that adsorption properties are strongly influenced by the character of the suface. The adsorption capacity of these samples can be utilized for the treatment of strongly polluted industrial waste waters. Considering that the raw material ‘needed’ to manufacture these adsorbent is produced permanently and the adsorbents do not have to be regenerated, it might be worthwhile using these kinds of adsorbents in the primary treatment of industrial waste waters.     

Selective Enrichment of a Methanol-Utilizing Consortium Using Pulp and Paper Mill Waste Streams

Efficient utilization of carbon inputs is critical to the economic viability of the current forest products sector. Input carbon losses occur in various locations within a pulp mill, including losses as volatile organics and wastewater. Opportunities exist to capture this carbon in the form of value-added products such as biodegradable polymers. Waste-activated sludge from a pulp mill wastewater facility was enriched for 80 days for a methanol-utilizing consortium with the goal of using this consortium to produce biopolymers from methanol-rich pulp mill waste streams. Five enrichment conditions were utilized: three high-methanol streams from the kraft mill foul condensate system, one methanol-amended stream from the mill wastewater plant, and one methanol-only enrichment. Enrichment reactors were operated aerobically in sequencing batch mode at neutral pH and 25°C with a hydraulic residence time and a solids retention time of 4 days. Non-enriched waste activated sludge did not consume methanol or reduce chemical oxygen demand. With enrichment, however, the chemical oxygen demand reduction over 24-h feed/decant cycles ranged from 79 to 89%, and methanol concentrations dropped below method detection limits. Neither the non-enriched waste-activated sludge nor any of the enrichment cultures accumulated polyhydroxyalkanoates (PHAs) under conditions of nitrogen sufficiency. Similarly, the non-enriched waste activated sludge did not accumulate PHAs under nitrogen-limited conditions. By contrast, enriched cultures accumulated PHAs to nearly 14% on a dry weight basis under nitrogen-limited conditions. This indicates that selectively enriched pulp mill waste activated sludge can serve as an inoculum for PHA production from methanol-rich pulp mill effluents.     

Isolation of PHA–Producing Bacteria from Date Syrup Waste

Since the major problem associated with the industrial production of Polyhydroxyalkanoates (PHAs) is their high production cost, this study was carried out using date syrup as the major carbon source to decrease the production cost and also help to supply other nutrient requirements. To isolate PHA–producing bacteria for this purpose, microorganisms were isolated from the syrup waste of a local date factory. These purified colonies were screened for intracellular granules by staining with Sudan Black. The positive-staining strains were grown for production of PHAs in 5% date syrup as carbon source supplemented with mineral salt medium. The culture was incubated at 30 °C with shaking at 140 rpm for 60 h. Among positively stained bacteria, the best PHA producers were selected on the basis of cell growth, cell dry weight, PHA content and the monomer composition of PHA. One of them could utilize date syrup for growth and produce the homopolymer of Polyhydroxybutyrate (PHB) with a cell density of about 5.1 g/L and maximum concentration of PHB equal to 3.6 g/L which is 71% of cell dry weight. Another one produces copolymer of Poly (hydroxybutyrate-hydroxyvalerate) in date syrup media with a maximum concentration of 2.2 g/L containing 10 wt % valerate in shake flask cultivation.     

Biomaterials from beer manufacture waste for bone growth scaffolds

Abstract

Agricultural wastes are a source of renewable raw materials (RRM), with structures that can be tailored for the use envisaged. Here, they have proved to be good replacement candidates for use as biomaterials for the growth of osteoblasts in bone replacement therapies. Their preparation is more cost effective than that of materials presently in use with the added bonus of converting a low-cost waste into a value-added product. Due to their origin these solids are ecomaterials.

In this study, several techniques, including X-ray diffraction (XRD), chemical analysis, mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and bioassays, were used to compare the biocompatibility and cell growth of scaffolds produced from beer bagasse, a waste material from beer production, with a control sample used in bone and dental regenerative processes.     

Bacterial polyhydroxyalkanoates-eco-friendly next generation plastic: Production,biocompatibility, biodegradation,physical properties and applications

ABSTRACT

Polyhydroxyalkanoates (PHAs) are intracellular aliphatic polyesters synthesized as energy reserves, in the form of water-insoluble, nano-sized discrete and optically dense granules in cytoplasm by a diverse bacteria and some archae under conditions of limiting nutrients in the presence of excess carbon source. Bacteria synthesize different PHAs from coenzyme A thioesters of respective hydroxyalkanoic acid, and degrade intracellularly for reuse and extracellularly in natural environments by other microorganisms. In vivo, PHAs exist as amorphous mobile liquid and water-insoluble inclusions but in vitro, exhibit material and mechanical properties, ranging from stiff and brittle crystalline to elastomeric and molding, similar to petrochemical thermoplastics. Further, they are hydrophobic, isotactic, biocompatible and exhibit piezoelectric properties. But as commodity plastics their applications are limited by high production cost, low yield, in vivo degradation, complexity of technology and difficulty of extraction. Therefore, to replace the conventional plastic with PHAs, it is prerequisite to standardize the PHA production systems.     

The effect of carbonisation temperatures on nanoporous characteristics of activated carbon fibre (ACF) derived from oil palm empty fruit bunch (EFB) fibre

Activated carbon fibre (ACF) is a nanoporous material which is useful for various important applications such as safe biogas and natural gas storage as well as heavy/precious metals removal and recovery. It is commonly produced from synthetic fibres such as rayon, polyacrylnitrile and pitch mainly derived from petroleum products, which are less environmental friendly. Besides, cost of ACF production is high due to the high burnt off percentage of such expensive raw materials. As an alternative, natural fibre of oil palm empty fruit bunch was used as a raw material for ACF preparation. Thermogravimetric analysis was carried out with two different gases, i.e. nitrogen gas and oxygen gas in order to observe pyrolysis and combustion behaviours in different gases. Carbonisation temperatures were then identified from the peaks of derivative thermogravimetry results. Different carbonisation temperatures (85?C200?°C) were chosen to carbonise the EFB fibre to observe the effect of carbonisation temperatures on the nanoporous characteristics, i.e. surface area, pore size distribution and pore volume of the ACF produced. Good nanoporous characteristics such as surface area up to 2,740?m²/g of the ACF prepared were observed, suggesting EFB fibre as an excellent candidate to replace synthetic fibre for ACF production. The discussion of relationship between thermal characteristics and nanopores in ACF derived from EFB were also included in this study.     

Degradable and Recyclable Polyesters from Multiple Chain Length Bio- and Waste-Sourceable Monomers

Monomers sourced from waste or biomass are often mixtures of different chain lengths; e.g. catalytic oxidation of polyethylene waste yields mixtures of dicarboxylic acids (DCAs). Yet, polyesters synthesized from such monomer mixtures have rarely been studied. We report polyesters based on multiple linear aliphatic DCAs, present in chain length distributions that vary in their centers and ranges. We demonstrate that these materials can adopt high-density polyethylene-like solid state structures, and are ductile (e.g. E_t 610 MPa), allowing for injection molding, or film and fiber extrusion. Melting and crystallization points of the polyesters show no odd-even effects as dipoles cannot favorably align in the crystal, similar to traditional odd carbon numbered, long-chain DCA polyesters. Biodegradation studies of ¹³C-labelled polyesters in soil reveal rapid mineralization, and depolymerization by methanolysis indicates suitability for closed-loop recycling.     

Industrial wastewater treatment wastes used as oxygen carriers in energy generation processes

The paper contains the results of a study on a promising combustion technology known as chemical looping combustion (CLC). The main advantage of CLC is the production of a highly concentrated CO₂ stream without any energy penalty for its separation, together with NO_x emissions reduction. The objective of this work was to examine novel oxygen carrier (OC) materials for their practical applications with gaseous fuel/air. We report a simple, economical and environmentally friendly method for the large-scale synthesis of OCs from wastes. The reactivity tests for OCs made from wastewater from a coking plant were performed in a thermogravimetric analyser. For selected temperatures, reduction–oxidation cycles were performed. The effect of temperature on the reaction rates, the effect of waste treatment and the oxygen transport capacity were determined. The waste material demonstrated good thermal stability and maintained its redox behaviour over cycling. ICP-OES and XRD data revealed these materials that contained beneficial amounts of Fe species and silicon oxide, which improved stability. The study showed that these waste materials are excellent examples of raw materials that can enable a decrease in OC production costs with the additional benefit of the practical management of post-wastewater sediments from coke oven wastewater plants.

     

Production of polyhydroxyalkanoates by fermentation of bacteria

Polyhydroxyalkanoates (PHAs) are carbon and energy reserve material accumulated by numerous microorganisms and have been drawing much attention as biodegradable substitutes for conventional nondegradable plastics and elastomers. There are a number of different PHAs having a variety of material properties based on the different monomer composition. Poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) are now efficiently produced by bacterial fermentation at reasonable production costs. Recent advances in the production of short‐chain‐length (SCL) PHAs by bacterial fermentation are reviewed. Current status of the production of medium‐chain‐length (MCL) PHAs and SCL‐MCL‐PHA copolymers is also reviewed.