Eman H. Gatea٭(1) Saad H. Khudair(1) and Nadhim H. Haider(2)
(1). Environment and Water Directorate, Ministry of Science and Technology, Baghdad, Iraq.
(2). Collage of science, Baghdad University, Baghdad, Iraq.
(*Corresponding author: Dr Eman Gatea. E-mail: eman77aa@yahoo.com).
Received: 04/11/2017 Accepted: 14/12/2017
Abstract
Polyhydroxya lkanoates (PHAs), are a promising family of bio-based polymers, which considered to be alternatives to traditional petroleum-based plastics. Poly-β – hydroxybutyrate (PHB) is the most known degradable biopolymers, produced by bacterial genera. It is generally accepted that PHB can be used instead of plastic to solve one of the greatest problems facing the environment. Pseudomonas aeruginosa Dw7 was grown on mineral salt medium supplemented with waste cooking of corn oil for the synthesis of a medium chain-PHB. This study is divided into three steps, at first fermentation of P.seudomonas aeruginosa Dw7, which was carried out aerobically at optimum temperature of 30 ˚C and 500 rpm of agitation speed. Lab scale bioreactor (5L) operated as a batch culture system for 80 hours. The highest cell dry weight (CDW) of bacteria reached to 5.3 g/l observed after 60 h of operation, which was corresponding to 62.6 % of PHB. The results suggested the efficiency of the system for production of PHB in large scale. Many solvent systems were conducted to evaluate the best solvent for PHB extraction from bacterial cell in the second step. Chloroform–hypochlorite dispersion extraction was followed by that extraction with chloroform showed the best solvent system for yielding of PHB. Relatively; it has the high rate with 63% yield of PHB. Characterization study of PHB was the last step. PHB were included chemical, physical; mechanical and solubility properties of the produced PHB have been characterized by many analyses techniques, comprising Gas Chromatography Mass Spectrometry (GC-MS), Fourier-transform Infrared Spectroscopy (FTIR), X-Ray diffraction (X-Ray) and melting point. PHB was a yellowish white crystal, soluble in chloroform and other chlorinated hydrocarbons like dichloromethane, dichlorethane and chloropropane. X-Ray diffraction (XRD) study was carried out to check if the polymer had a crystalline or amorphous structure. The increased intensity of peaks showed that the polymer had more organized packed crystalline structure. The results of the GC-MS recorded that there were 9 different active peaks predictive. The two major compounds that were produced by P. aeruginosa Dw7 were then identified as undecanoic acid which eluted at 15.4 min and tridecanoic acid at 17.3 min with relative abundance of 100% and 33.14% respectively. The characteristic FTIR peaks for PHB indicated that the most prominent marker band for the identification of PHB is the ester carbonyl band at C=O, OH and C-O.
Keywords: Pseudomonas aeruginoa, Poly-β- hydroxybutyrate, Bioreactor, Extraction with solvents.
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