Physico-chemical Characterization of Poly(3-Hydroxybutyrate) Produced by Halomonas salina, Isolated from a Hypersaline Microbial Mat (original) (raw)
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Poly-β-hydroxybutyrate (PHB) is the intracellular lipid reserve accumulated by many bacteria. The most potent terrestrial bacterium Bacillus cereus SE-1 showed more PHB accumulating cells (22.1 and 40% after 48 and 72 h) than that of the marine Bacillus sp. CS-605 (5 and 33% after 48 and 72 h). Both the isolates harbored phbB gene and the characteristics C=O peak was observed in the extracted PHB by Fourier transformed infrared spectroscopy analysis. Maltose was found to be the most suitable carbon source for the accumulation of PHB in B. cereus SE-1. The extracted PHB sample from B. cereus SE-1 was blended with a thermoplastic starch (TS) and an increased thermoplasticity and decreased crystallinity were observed after blending in comparison to the standard PHB. The melting temperature (T m ), melting enthalpy (ΔHf), and crystallinity (X c ) of the blended PHB sample were found to be 109.4°C, 64.58 J/g, and 44.23%, respectively.
Polyhydroxyalkanoates (PHAs) are bacterial polymers that are formed as naturally occurring storage polyesters by a wide range of microorganisms. Biodegradable and biocompatible poly(3-hydroxybutyrate) (PHB) and its copolymers with 3-hydroxyvalerate (PHBV) are the best known representatives of PHA family. For more than 20 years biosynthesis, biodegradation and applications of PHB and its copolymers have been studied in the Bach Institute of Biochemistry RAS. An effective technology for production of PHB and PHBV of different molecular weight (from 200 to 1500 kDa) by diazotrophic bacteria of Azotobacter and Rhizobium genus has been developed. In order to clarify mechanism of PHB biodegradation degradation of PHB at different conditions in vitro and in vivo have been studied. A number of medical devices on basis of PHB: surgical meshes, screws and plates for bone fixation, periodontal membranes, and wound dressing are developed. High biocompatibility of PHB films and medical devices implanted in animal tissues has been demonstrated. Nowadays, development of systems of sustained drug delivery on the base of PHAs microspheres and microcapsules as a new and promising trend in the modern pharmacology is intensively in progress.
Polymers
Plastic pollution is fueling the grave environmental threats currently facing humans, the animal kingdom, and the planet. The pursuit of renewable resourced biodegradable materials commenced in the 1970s with the need for carbon neutral fully sustainable products driving important progress in recent years. The development of bioplastic materials is highlighted as imperative to the solutions to our global environment challenges and to the restoration of the wellbeing of our planet. Bio-based plastics are becoming increasingly sustainable and are expected to substitute fossil-based plastics. Bioplastics currently include both, nondegradable and biodegradable compositions, depending on factors including the origins of production and post-use management and conditions. Among the most promising materials being developed and evaluated is polyhydroxybutyrate (PHB), a microbial bioprocessed polyester belonging to the polyhydroxyalkanoate (PHA) family. This biocompatible and non-toxic polyme...
Bioresource Technology, 2011
Characterisation of polyhydroxyalkanoate (PHA) film produced by haloalkalitolerant Halomonas campisalis (MCM B-1027) in 14 L SS fermenter revealed it to have composition of monomer units, HB:HV as 96:4 as analysed by 1 H NMR indicating the PHA as a co-polymer of PHB-co-PHV, molecular weight by gel permeation chromatography as 2.08 Â 10 6 , melting temperature 166.51°C, tensile strength 18.8 MPa; two relaxations namely beta transition corresponding to the glass rubber transition and alpha transition corresponding to crystalline relaxation by Dynamic Mechanical Thermal analysis and only one relaxation corresponding to MWS interfacial polarisation with activation energy of 129 kJ/mol by broadband dielectric spectroscopy. Optical microscopic studies showed typical Maltese-cross pattern of spherulites. The PHA film was found to be biodegradable by standard ASTM method as well as by soil burial method. The leak proof polymer bags prepared from the film could be used as a packaging material.
Bioresource Technology, 2018
This work explores molecular, morphological as well as biotechnological features of the highly promising polyhydroxyalkanoates (PHA) producer Halomonas halophila. Unlike many other halophiles, this bacterium does not require expensive complex media components and it is capable to accumulate high intracellular poly(3-hydroxybutyrate) (PHB) fractions up to 82 % of cell dry mass. Most remarkably, regulating the concentration of NaCl apart from PHB yields influences also the polymer´s molecular mass and polydispersity. The bacterium metabolizes various carbohydrates including sugars predominant in lignocelluloses and other inexpensive substrates. Therefore, the bacterium was employed for PHB production on hydrolysates of cheese whey, spent coffee grounds, saw dust and corn stover, which were hydrolyzed by HCl; required salinity of cultivation media was set up during neutralization by NaOH. The bacterium was capable to use all the tested hydrolysates as well as sugar beet molasses for PHB biosynthesis, indicating its potential for industrial PHB production.
Viscoelastic and thermal properties of bacterial poly(d-(−)-β-hydroxybutyrate)
International Journal of Biological Macromolecules, 1988
Three poly(D-(-)-fl-hydroxybutyrate) (PH B) samples from Rhizobium spp. have been characterized in order to evaluate the effects of different extraction procedures of the polymer. Only the molecular weight is found to change, being 6 x 104 for the sample extracted with H CI (1 M) and of the order of lO ~ for the samples extracted with acetone. Thermogravimetric results on PHB with different molecular weights, indicate that the temperature at which weight loss becomes significant is lower than 230°C only for the lowest molecular weioht examined (6 x 104). The calorimetric properties strongly depend on thermal history. The d.s,c, curves of 'room stored' samples show only a melting endotherra at 177°C, whose area increases ~ annealiag. Quenching from the melt shows evidence an intense glass transition (ACp=O.43 J/g deg) in the vicinity of O°C, followed by a 'cold crystallization' peak preceding melting. The viscoelastic spectrum shows three relaxations: a water-related low temperature relaxation (-80°C), the glass transition (apparent activation energy AHo=356 KJ/mol) and a broad relaxation in the temperature range between T o and Tm due to motions in the crystalline phase.
Molecules
This work aims to characterize the haloarchaeal diversity of unexplored environmental salty samples from a hypersaline environment on the southern coast of Jeddah, Saudi Arabia, looking for new isolates able to produce polyhydroxyalkanoates (PHAs). Thus, the list of PHA producers has been extended by describing two species of Halolamina; Halolamina sediminis sp. strain NRS_35 and unclassified Halolamina sp. strain NRS_38. The growth and PHA-production were investigated in the presence of different carbon sources, (glucose, sucrose, starch, carboxymethyl cellulose (CMC), and glycerol), pH values, (5–9), temperature ranges (4–65 °C), and NaCl concentrations (100–350 g L−1). Fourier-transform infra-red analysis (FT-IR) and Liquid chromatography–mass spectrometry (LC-MS) were used for qualitative identification of the biopolymer. The highest yield of PHB was 33.4% and 27.29% by NRS_35 and NRS_38, respectively, using starch as a carbon source at 37 °C, pH 7, and 25% NaCl (w/v). The FT-IR...