In vitro degradation of poly[(r)-3-hydroxybutyrate] and BIOPOL™ by marine-derived fungi

Abstract

As part of efforts to conserve global resources and reduce pollution, the search for new bio-synthetic/bio-degradable materials remains an urgent task. Poly[(R)-3-hydroxyalkanoates] (PHAs) are synthesized by bacteria and display thermoplastic properties. The most common bacterial bio-synthetic PHAs are poly[(R)-3-hydroxybutyrate] (PHB), poly[(R)-3-hydroxyvalerate] (PHV) and their copolymers. PHB and PHV are already commercially produced and used as BIOPOL™ (ICI) for packaging purposes. Oceans and estuaries often serve as major landfills and fungi are an important component of their biodegradation microbiota. In order to characterize the role of fungi in marine biodegradation processes, a simple degradation test suitable for fungi in partially simulated marine conditions had to be developed. Thirty-two strains of yeasts and 102 strains of mycelial fungi isolated from marine habitats and belonging to different systematic and ecological groups were tested for their ability to degrade PHAs. Only approximately 4.5% of the strains were able to degrade BIOPOL^TM and about 6.7% depolymerized pure PHB homopolymers. This is in sharp contrast to the results of our previous experiments with 143 strains of terrestrial fungi which showed that more than 55% were able to degrade BIOPOL™. Among ascomicetous fungi, one strain of Asteromyces cruciatus, one strain of Candida guilliermondii, and two strains of Debaryomyces hansenii were able to degrade PHB or both PHB and BIOPOL™. Active basidiomicetous fungi were represented by one strain of Nia vibrissa and one strain of Rhodosporidium sphaerocarpum that were able to depolymerize PHB, but not BIOPOL™.