Results and Discussion
Isolation and identification of polyester-degrading strains
Total sixty actinomycetes strains were collected from compost soils in Thailand. After incubation for 4 days at 45°C, the colonies were appeared on polyester agar plates. Strain TF1 could degrade all of bioplastics and had the highest clear zone on PBS-agar plate then was selected as the best strain to study. The result suggested that strain TF1 had a wide range of degradation activities of biodegradable plastics. A circular clear zone formed surrounding each colony as shown in Figure 1. This happens when bioplastic can be emulsified into an agar matrix and bioplastic-degrading microorganisms excrete extracellular enzymes which diffuse though the agar and degrade bioplastic to water soluble materials 124]. Clear zone technique is a powerful method forecological investigation of bioplastics degradation [19]. Sequence analysis of 16S rDNA gene of strain TF1 (1,358 bases; accession no. KC529344) showed 99% identity with Actinomadura miaoliensis. The various thermophilic actinomycetes are able to degrade polyesters from different environments, such as Amycolatopsis sp. strain K104-113 Actinomadura miaoliensis strain BCA AT-5 [4], Actinomadura keratinilytica strain T16-1 (5], Streptomyces thermoviolaceus subsp. thermoviolaceus 7 [6], Thermomonospora fusca [7] and Laceyella sacchari LP 175 18l. Tseng et al [4] reported that Actinomadura miaoliensis strain BC44T-5 was isolated from Miaoli country, Taiwan and had ability to degrade only PHB