Breeding Of Aspergillus Sp. DS0906to Degrade P3/4HB And Characteirzation Of P3/4HB Depolymerase

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)(P3/4HB) is the forth generationof polyhydroxyalkanoates (PHAs) polyester, with better mechanical properties、 biodegradability and biocompatibility than PHB or PHBV. So it deserves to study.However the study of P3/4HB is just restricted to the synthetize of P3/4HB and latermodification. There is less study in the biodegradation of P3/4HB. In this article, weisolated a fungus strain to biodegrade P3/4HB from the industrial sewage, and studiedthe strain’s substrate specificity, the isolation and purification of P3/4HBdepolymerase, and the fundamental characteristics of the P3/4HB depolymerase. Themain results obtained form this work are as follows:1. The isolation and identification of P3/4HB degradation fungus. The P3/4HBdegradation fungus was isolated with the dilution coating method from the industrialsewage. Through the morphological analysis and ITS sequence analysis, weconfirmed the fungus belongs to Aspergillus fumigates, and named it Aspergillus sp. DS0906.2. The substrate specificity of strain DS0906. Through the solid plate andenzyme activity method, we found the strain can be concentrated to degrade PHAspolyester, and can’t degrade PBS, PCL and PLA. The biodegrability is as follows:P3/4HB> PHBV>PHB>emulsive P3/4HB.3. The isolation and purification of P3/4HB depolymerase, and the maincharacteristics of the P3/4HB depolymerase. Through the method of ammoniumsulfate precipitation and hydrophobic gel chromatography, we purified the P3/4HBdepolymerase with two other proteins. It is preliminarily presumed that the molecularweight of P3/4HB depolymerase is34kDa or so. The optimum temperature of crudeenzyme is60℃, the temperature stability is better from10℃to50℃. The optimumpH is6.0, and stable from pH6.0to8.0.4. The enzymolysis of P3/4HB film. The rate of P3/4HB film’s enzymolysisquickened gradually, and it’s tensile strength decreased gradually until broken. Themain reason is the varying thickness of the film caused by enzymolysis, nothing to dowith the molecular weight of the film.5. The determination of degradation products. The final degradation products ofP3/4HB is3-hydroxybutyrate and4-hydroxybutyrate rather than the dipolymer ofboth.