Biodegradation of microbial polyesters P(3HB) and P(3HB- co-3HV) under the tropical climate environment

Abstract

The biodegradation of poly(3-hydroxybutyrate), P(3HB), and its copolymer poly(3-hydroxybutyrate- co-3-hydroxyvalerate), P(3HB- co-3HV) produced by a locally isolated bacteria identified as Erwinia sp. USMI-20 were carried out by using soil burial test and immersion test method at various places under the tropical environment in West Sumatra, Indonesia. The isolation of P(3HA)-degrading microorganisms was done by the in vitro rapid plate test method and was further characterized by using biochemical reactions. Our results showed that P(3HB) biodegraded at a rate of 3.6% per week in activated sludge, 1.9% per week in soil, 1.5% per week in lake water and 0.8% per week in Indian Ocean sea water. The degradation rates for P(3HB- co-3HV) were 17.8% per week in activated sludge, 6.7% per week in soil, 3.2% per week in lake water and 2.7% per week in Indian Ocean sea water. The biodegradation of both polymers were highest after burial into activated sludge with a half-life ( T 1/2) of 14 weeks and the time for 100% degradation ( T∼ 100%) of 28 weeks for P(3HB), and a T 1/2 of 3 weeks and T∼ 100% at 6 weeks for P(3HB- co-3HV). In this study, 10 bacteria which were responsible for the biodegradation of P(3HB) and P(3HB- co-3HV) film were isolated and identified from the various places studied under the tropical environment. They were Bacillus sp. FAAC-2202, Enterobacter sp. FAAC-2207, Bacillus sp. FAAC-2209 and Proteus sp. FAAC-2203 obtained from activated sludge, Bacillus sp. FAAC-2201 and Alcaligenes sp. FAAC-2210 from soil, Alcaligenes sp. FAAC-2205, Micrococcus sp. FAAC-2206 and Pseudomonas sp. FAAC-2208 from lake water and Proteus sp. FAAC-2204 from Indian Ocean sea water.