An aliphatic aromatic copolyester, poly(butylene adipate-co-terephthalate) (PBAT) is a chemically synthetic and biodegradable polymer that exhibits good mechanical properties, similar to those of low-density polyethylene (LDPE), and can be a replacement for LDPE as biodegradable mulch films in the agricultural field. Biodegradability of PBAT is stable at high temperature conditions (50 – 60 ˚C) such as compost environments compared to mild temperature conditions (25 – 37 ˚C) such as soil environments. Considering that PBAT could be used in biodegradable agricultural applications such as mulching film, it is important to investigate the biodegradation mechanism at mild temperatures. In this study, a PBAT-degrading bacterium isolated from a soil environment, designated as strain NKCM 2511, was studied in detail. Genetic and biochemical analysis revealed that the strain belongs to the genus Rhodococcus in the phylum Actinobacteria. The strain grew only in aerobic conditions and formed a clear zone on a PBAT containing plate in the temperature range of 20 ˚C to 30 ˚C. Based on biochemical oxygen demand (BOD) biodegradation testing, among 3 PBAT components, adipicacid and terephthalic acid resulted in low growth rate of the strains (5 % and 7 %, incubated at 25 °C for 20 days), whereas 1,4-butanediol resulted in good growth of the strains (55 %). The low BOD biodegradation rate of PBAT by this strain (7 %) may be due to such low rates of terephthalic and adipic acid. Additionally, the PBAT degradation rate was proportional to the growth rate in the presence of various carbon sources. Therefore, the strain was an aerobically mesophilic PBAT-degrading bacterium that expressed the PBAT-degrading enzyme constitutively. To our knowledge, this is the first report on a PBAT-degrading actinobacterial strain in mild conditions. This study provides information to better understand the biodegradation mechanism of PBAT under mild conditions such as in fields.

脂肪族芳香族共聚酯，聚（亚丁基己二酸酯共-对苯二甲酸酯（PBAT）是一种化学合成且可生物降解的聚合物，与低密度聚乙烯（LDPE）相似，具有良好的机械性能，可替代LDPE作为农业领域的可生物降解覆盖膜。与诸如土壤环境的中等温度条件（25 – 37℃）相比，PBAT的生物降解性在堆肥环境等高温条件下（50 – 60˚C）是稳定的。考虑到PBAT可以用于可生物降解的农业应用（例如覆盖膜），因此研究温和温度下的生物降解机理非常重要。在这项研究中，详细研究了从土壤环境中分离出的PBAT降解细菌，命名为NKCM 2511菌株。遗传和生化分析表明该菌株属于该属红球菌在门放线菌中。菌株仅在有氧条件下生长，并在20°C至30°C的温度范围内在包含PBAT的板上形成一个清晰的区域。根据生化需氧量（BOD）生物降解测试，在3种PBAT成分中，己二酸和对苯二甲酸导致菌株的生长速率较低（5％和7％，在25°C下孵育20天），而1,4-丁二醇使菌株生长良好（55％）。这种菌株对PBAT的BOD生物降解率较低（7％）可能是由于对苯二甲酸和己二酸的降解率较低。此外，在存在各种碳源的情况下，PBAT降解速率与生长速率成比例。因此，该菌株是需氧嗜温的PBAT降解细菌，其组成性表达PBAT降解酶。据我们所知，这是关于在温和条件下降解PBAT的放线菌菌株的首次报道。这项研究提供了信息，以更好地了解在野外等温和条件下PBAT的生物降解机理。