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Biodegradation of blends of bacterial poly(3‐hydroxybutyrate) with ethyl cellulose in activated sludge and in enzymatic solution
Author(s) -
Finelli Lara,
Scandola Mariastella,
Sadocco Patrizia
Publication year - 1998
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19980401)199:4<695::aid-macp695>3.0.co;2-e
Subject(s) - biodegradation , cellulose , activated sludge , ethyl cellulose , materials science , polymer blend , compression molding , chemistry , scanning electron microscope , chemical engineering , polymer chemistry , polymer , organic chemistry , composite material , copolymer , sewage treatment , waste management , mold , engineering
Blends of poly(3‐hydroxybutyrate) (PHB) and ethyl cellulose (EtC) were prepared by compression molding of solution cast films. The two components were not miscible but the blends showed ‘mechanical compatibility’. Two PHB/EtC blends (80/20 and 50/50 (w/w in all cases)) were selected for biodegradation experiments in activated sludge and in enzymatic solution of PHB‐depolymerase from Pseudomonas lemoignei and from Aureobacterium saperdae . Blend morphology was quite different: blend 80/20 was composed of a matrix of impinging PHB spherulites with dispersed EtC inclusions, whereas blend 50/50 was constituted of two continuous phases with interpenetrated domains. Both blends biodegraded in activated sludge, but only blend 80/20 was attacked by PHB‐depolymerases from P. lemoignei and A. saperdae . From weight loss, thickness and composition measurements after different exposure times and from scanning electron microscopy of the biodegraded blend surface it was concluded that in blend 80/20 biodegradation of the PHB matrix caused concomitant release in the medium of the embedded EtC particles. The results on PHB/EtC (50/50) after sludge exposure demonstrated that in this blend the PHB phase – thanks to its interconnected domains – was continuously accessible to microbial attack, leaving a highly cavitated ethyl cellulose structure after PHB consumption. The lack of biodegradation of blend 50/50 in enzymatic solution was tentatively attributed to changes of surface hydrophobicity induced by large amounts of EtC, which disfavored enzyme binding.