A poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)]-degrading strain was isolated and identified as Paecilomyces sp. A novel P(3HB-co-4HB) depolymerase with a molecular weight of 55 kDa was purified by column chromatography from the culture supernatant of the strain. The purified depolymerase showed optimum activity at pH 6.0 and 30 °C, and it was stabilized at pH 4.0–7.0 and below 40 °C. The depolymerase degraded poly(3-hydroxybutyrate) (PHB), poly(hydroxybutyrate-co-hydroxyvalerate), and several short-chain-length esters other than P(3HB-co-4HB) but showed no remarkable activity on poly(ε-caprolactone) and poly(L-lactic acid). The main enzymatic products comprised hydroxybutyrate monomers, including 3HB and 4HB. The enzymatic erosion rate on the films increased markedly with increasing fraction of 4HB units. Enzymatic hydrolysis processes of PHB and P(3HB-co-4HB) were systematically analyzed in three aspects: enzyme adsorption, single-polymer-chain dissociation, and chemical linkage breakdown. Results indicate that 4HB insertion caused no effect on the degradation of solid-phase PHB-derived material at the molecular chain level but affected enzyme adsorption and crystallinity of the materials. Hindering single-chain stripping by crystallinity dominantly affects the degradation behavior of the polymer.

甲聚（3-羟基丁酸酯共-4-羟基丁酸酯）[P（3HB-共-4HB）] -降解菌分离并鉴定为拟青霉属。通过柱色谱法从菌株的培养上清液中纯化了分子量为55kDa的新型P（3HB- co- 4HB）解聚酶。纯化的解聚酶在pH 6.0和30°C下显示最佳活性，在pH 4.0-7.0和40°C以下稳定。解聚酶降解了聚（3-羟基丁酸酯）（PHB），聚（羟基丁酸酯-共-羟基戊酸酯）和除P（3HB- co以外的几种短链酯-4HB），但对聚（ε-己内酯）和聚（L-乳酸）没有明显的活性。主要的酶促产物包括羟基丁酸酯单体，包括3HB和4HB。随着4HB单位分数的增加，膜上的酶侵蚀速率显着增加。从以下三个方面系统分析了PHB和P（3HB- co -4HB）的酶水解过程：酶吸附，单聚合物链解离和化学键断裂。结果表明，插入4HB不会在分子链水平上影响固相PHB衍生材料的降解，但会影响材料的酶吸附和结晶度。通过结晶度阻碍单链剥离主要影响聚合物的降解行为。