Abstract

The biodegradation of poly (tetramethylene adipate-co-tetramethylene terephthalate) (BTA-copolyester) as synthetic polyester was investigated under thermophilic conditions. Two efficient BTA degrading actinomycetes were isolated from compost at thermophilic phase. These strains were identified as Thermobifida fusca and Thermobispora bispora. The degradation rate for BTA films within 7 days was 17.12 and 16.96 mg/week.cm² by T. fusca and T. bispora, respectively. The optimum BTA40:60 degradation conditions are obtained as pH7 and 55°C. The both strains exhibited a wider substrate spectrum as they are able to degrade synthetic polyesters (BTA40:60, PCL-S MaterBi ZF03U/A) and natural polymers (poly-β-hydroxybutyric acid (PHB) and carboxymethyl cellulose). It was shown that the extracellular hydrolyases activity from the both strains was induced in the presence of BTA- copolyester, while the presence of additional carbon sources such as glucose or a complex medium suppressed enzyme formation. Tributyrin as triglycerides was degraded by the both crude concentrated BTA-hydrolases. In contrast the enzyme was not capable to depolymerize the natural polymers PHB and carboxymethyl cellulose, although the organism itself degraded both types of polymers. The obtained results showed that the degradation rate with T. fusca BTA40:60-hydrolase was 3.67 mg/day.cm² and was 3.5 mg/day.cm² with T. bispora BTA40:60- hydrolase. The pH optimum for BTA-hydrolases was 7 with 20 and 100 mM phosphate buffer and it was 6 with 150 mM citrate buffer. Finally, it could be concluded that actinomycetes and their hydrolases play an outstanding role in recycling of biodegradable plastics under thermophilic phase during composting process.

Keywords:

Actinomycetes, Biodegradation, Bioplastic, enzymatic degradation, thermophilic conditions,

References

Competing interests

The authors have no competing interests.

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The authors have no competing interests.