Department of Biotechnology, Indian Institute of Technology Madras, S.P Road, Adyar, Chennai 600036, India.
Enzyme Microb Technol. 2011 Jan 5;48(1):71-9. doi: 10.1016/j.enzmictec.2010.09.011. Epub 2010 Oct 12.
The biodegradation of an engineering thermoplastic, poly (bisphenol-A carbonate) (BPAPC), was carried out using three different lipases from Candida antarctica (CAL), Candida rugosa (CRL) and porcine pancreas (PPL) in water-miscible (tetrahydrofuran) and water-immiscible (chloroform) solvents for 10 days. The degradation was monitored by gel permeation chromatography and Fourier transform infrared spectroscopy. Maximum degradation (ca. 60% reduction in M(n)) of BPAPC was observed in THF with PPL when compared to the control without the enzyme. The degradation products in all the experiments were bisphenol-A and 4-α-cumyl phenol suggesting that the lipases act through an end-chain scission on the polymer. The degradation of BPAPC in THF was in the order of PPL>CAL>CRL, while in CHCl(3) it was CRL>CAL>PPL. To understand this disparity, and to probe the mechanistic aspects of degradation, molecular dynamics investigations were performed on the lipases with model BPAPC in both the solvents. The results also suggested that catalytic triad (Ser, His, Asp/Glu) was involved in the hydrolysis of carbonate bond leading to release of bisphenol-A. These data provide us the basic understanding of the degradation mechanism and a novel methodology for degrading polycarbonate.
使用三种不同的脂肪酶（南极假丝酵母脂肪酶（CAL）、皱褶假丝酵母脂肪酶（CRL）和猪胰脂肪酶（PPL））在水混溶性（四氢呋喃）和水不混溶性（氯仿）溶剂中对工程热塑性塑料聚（双酚 A 碳酸酯）（BPAPC）进行了 10 天的生物降解。通过凝胶渗透色谱法和傅里叶变换红外光谱法监测降解情况。与没有酶的对照相比，在 THF 中使用 PPL 时，BPAPC 的最大降解（约 60%的 M(n)减少）。在所有实验中，降解产物均为双酚 A 和 4-α-枯基苯酚，表明脂肪酶通过聚合物的末端链断裂起作用。在 THF 中，BPAPC 的降解顺序为 PPL>CAL>CRL，而在 CHCl(3)中则为 CRL>CAL>PPL。为了理解这种差异，并探究降解的机制方面，我们在两种溶剂中对脂肪酶和模型 BPAPC 进行了分子动力学研究。结果还表明，催化三联体（Ser、His、Asp/Glu）参与了碳酸酯键的水解，导致双酚 A 的释放。这些数据为我们提供了降解机制的基本理解和降解聚碳酸酯的新方法。
