Surface changes in polyhydroxyalkanoate films during biodegradation and biofouling

BACKGROUND: Despite the recognition that microbial biofilms play a role in environmental degradation of bioplastics, few studies investigate the relationship between bioplastic biodegradation and microbial colonisation. We have developed protocols based on a combination of confocal laser scanning microscopy and contact angle goniometry to qualitatively and quantitatively map surface changes due to biofilm formation and biopolymer degradation of solvent cast poly (3-hydroxyalkanoate) films in an accelerated in vitro biodegradation system. RESULTS: A significant regression relationship between biofilm formation and polymer biodegradation (R-2 = 0.96) was primarily conducted by cells loosely attached to the film surfaces (R-2 = 0.95), rather than the strongly attached biofilm (R-2 = 0.78). During biodegradation the surface rugosity of poly(3-hydroxybutyrate) and poly[ (3-hydroxybutyrate)-co-(3-hydroxyvalerate)] increased by factors of 1.5 and 1.76, respectively. In contrast, poly(3-hydroxyoctanoate) films showed little microbial attachment, negligible weight loss and insignificant changes in surface rugosity. CONCLUSION: A statistically significant link is established between polymer weight loss and biofilm formation. Our results suggest that this degradation is primarily conducted by cells loosely attached to the polymer rather than those strongly attached. Biofilm formation and its type are dependent upon numerous factors; the flat undifferentiated biofilms observed in this study produce a gradual increase in surface rugosity, observed as an increase in waviness. (C) 2008 Society of Chemical Industry.