title: Biodegradation of starch films: the roles of molecular and crystalline structure.
abstract: The influences of molecular, crystalline and granular structures on the biodegradability of compression-molded starch films were investigated. Fungal α-amylase was used as model degradation agent. The substrates comprised varied starch structures obtained by different degrees of acid hydrolysis, different granular sizes using size fractionation, and different degrees of crystallinity by aging for different times (up to 14 days). Two stages are identified for unretrograded films by fitting degradation data using first-order kinetics. Starch films containing larger molecules were degraded faster, but the rate coefficient was independent of the granule size. Retrograded films were degraded much slower than unretrograded ones, with a similar rate coefficient to that in the second stage of unretrograded films. Although initially the smaller molecules or the easily accessible starch chains on the amorphous film surface were degraded faster, the more ordered structure (resistant starch) formed from retrogradation, either before or during enzymatic degradation, strongly inhibits film biodegradation.
authors.affiliation: School of Pharmacy, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China; The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane 4072, QLD, Australia.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane 4072, QLD, Australia.
authors.forename: Torsten
authors.initials: T
authors.lastname: Witt
authors.affiliation: The University of Queensland, Australian Institute for Bioengineering and Nanotechnology, Brisbane 4072, QLD, Australia.
authors.forename: Fengwei
authors.initials: F
authors.lastname: Xie
authors.affiliation: The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane 4072, QLD, Australia.
authors.forename: Frederick J
authors.initials: FJ
authors.lastname: Warren
authors.affiliation: The University of Queensland, Australian Institute for Bioengineering and Nanotechnology, Brisbane 4072, QLD, Australia; The University of Queensland, School of Chemical Engineering, Brisbane 4072, QLD, Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Halley
authors.affiliation: School of Pharmacy, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China; The University of Queensland, Centre for Nutrition and Food Sciences, Queensland Alliance for Agriculture and Food Innovation, Brisbane 4072, QLD, Australia. Electronic address: b.gilbert@uq.edu.au.
authors.forename: Robert G
authors.initials: RG
authors.lastname: Gilbert
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology; D006813:Humidity; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008970:Molecular Weight; D012995:Solubility; D013213:Starch / Q000737:chemistry* / Q000378:metabolism*; D013696:Temperature; D014867:Water / Q000737:chemistry; D000516:alpha-Amylases / Q000378:metabolism
chemical_list: D014867:Water; D013213:Starch; D000516:alpha-Amylases
keywords: Bioplastic; Crystallinity; Enzymatic degradation; Molecular structure; Starch