Biodegradation Studies of Polyhydroxybutyrate and Polyhydroxybutyrate-co-Polyhydroxyvalerate Films in Soil

Area of Science:

• Materials Science
• Environmental Science
• Biotechnology

Background:

• Growing environmental concerns necessitate alternatives to petrochemical plastics.
• Polyhydroxyalkanoates (PHAs) are microbial biopolymers offering biodegradability.
• Understanding PHA degradation is crucial for sustainable material development.

Purpose of the Study:

• To evaluate the degradation of polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-polyhydroxyvalerate (PHBV) under varying soil moisture conditions.
• To assess the impact of soil humidity on the physical and chemical properties of PHB and PHBV.
• To determine the potential of PHAs as replacements for conventional plastics in different environments.

Main Methods:

• Samples of PHB and PHBV were subjected to degradation in soil at 100% relative humidity (RH) and 40% RH.
• Degradation was monitored through visual inspection, chemical analysis, mechanical testing, and molecular weight determination.
• Comparative analysis of degradation rates under distinct soil moisture levels was performed.

Main Results:

• Complete degradation of both PHB and PHBV occurred within two weeks in 100% RH soil.
• Significant loss of mechanical properties was observed in samples after only three days at 100% RH.
• Minimal changes in mechanical properties, melting temperatures, crystallinity, and molecular weight were noted for samples in 40% RH soil over six weeks.

Conclusions:

• Soil moisture content is a critical factor influencing the biodegradation rate of PHB and PHBV.
• PHAs demonstrate rapid degradation in high-moisture environments, suggesting suitability for specific applications.
• The limited degradation in lower humidity soil indicates potential for use where slower biodegradation is desired or in less humid climates.