Degradation Of PHB And Characterization Of Extracellular PHB Depolymerase From DS9701-04 Strain

Poly(β-hydroxybutyrate)(PHB) is a kind of biodegradable polyester synthesized by prokaryote as intracellular strorage compounds of carbon and nitrogen. As a new biodegradable materials, it has attracted much commercial and academic interest and become a hot spot of the field of biomaterial in the whole world for its similar material property to conventional plastics and complete biodegradability under natural environment.PHB depolymerase is a kind of extracellular enzyme which is secreted by microbiology, and it could hydrolyse the polymer to water-soluble product. The aim of this work is to get the massage of the degradation of PHB from DS9701-04, to sepatate and purify PHB depolymerase and to study the fundamental characteristics of PHB depolymerase. The main results obtained from this work are as follows:1. The result of Penicillium sp. DS9701-04 to degrade PHB. In the Petri dish with PHB as only carbon source, the Penicillium sp. DS9701-04 grew into a great colony and surrounded by hyalo-ring which was cultivated for 5 days. It cost five days and nine days to degrade PHB powder and PHB film after inoculating the liquid of spore in liquid medium.2.The Penicillium sp. DS9701-04, a strain of degrading PHB, showed the most activity to secrete extracellular PHB depolymerase at 120h. The PHB depolymerase was separated from the culture medium by using ultra-filtration,ammonium sulfate precipitation,freezing exsiccation,gel filtration technique in Sephadex G-100. The activity of the purified eyzyme was increased by 196.44 folds over crude extract and the recovery yield was 10.67%.3. Some characteristics about PHB depolymerase: It is certified to be a singlespectrum by SDS-PAGE and the molecular weight is 36.4KD. he optimum activity of enzyme was observed at the temperature 30℃and at pH4.75. The range of temperature stability was below 40℃, the range of pH stability was from 4.36 to 7.22. Na+,K+,Mg2+,Ca2+ increased the enzyme activity, but the anzyme was inhibited by Fe3+,Fe2+,Ba2+,Zn2+. The mass spectrum analysis of fermentation was performed and the main product was indentified to be monomer and dipolymer.4. The amino acid composition of enzyme: Asp 14.488%;Glu 7.491%;Ser 8.070%; His 2.036%;Arg 2.287%; Gly 8.102%;Thr 9.882%;Pro 5.124%;Ala 7.296%;Val 7.044%;Met 2.122%;Ile 4.730%;Leu 7.452%;Phe 4.919%; Lys 3.856%;Tyr 5.100%。...