Bornadel Amin, Ismail Mohamed, Sayed Mahmoud, Hatti-Kaul Rajni, Pyo Sang-Hyun
Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, Box 124, Lund, SE-221 00, Sweden.
Microbiology Department, Faculty of Science, Helwan University, Cairo, Egypt.
Biotechnol Prog. 2017 Mar;33(2):375-382. doi: 10.1002/btpr.2406. Epub 2016 Dec 1.
Six-membered cyclic carbonates with hydroxyl and methoxycarbonyloxy functional groups were prepared by transesterification of trimethylolpropane (TMP) with dimethylcarbonate (DMC) by solvent-free lipase-mediated flow reaction followed by thermal cyclization. The flow reaction efficiency was evaluated using different configurations of reactor consisting of packed beds of Novozym®435 (immobilized Candida antarctica lipase B-CalB-a.k.a. N435) and molecular sieves, flowrate, and biocatalyst loads. The mixed column of the biocatalyst and molecular sieves, allowing rapid and efficient removal of the by-product-methanol-was the most efficient setup. Higher conversion (81.6%) in the flow reaction compared to batch process (72%) was obtained using same amount of N435 (20% (w/w) N435:TMP) at 12 h, and the undesirable dimer and oligomer formation were suppressed. Moreover, the product was recovered easily without extra separation steps, and the biocatalyst and the molecular sieves remained intact for subsequent regeneration and recycling. The reaction of CalB with DMC and the primary transesterification product, monocarbonated TMP, respectively, as acyl donors was evaluated by in silico modeling and empirically to determine the role of the enzyme in the formation of cyclic carbonates and other side products. DMC was shown to be the preferred acyl donor, suggesting that TMP and its carbonated derivatives serve only as acyl acceptors in the lipase-catalyzed reaction. Subsequent cyclization to cyclic carbonate is catalyzed at increased temperature and not by the enzyme. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:375-382, 2017.
通过无溶剂脂肪酶介导的流动反应使三羟甲基丙烷（TMP）与碳酸二甲酯（DMC）进行酯交换反应，随后进行热环化反应，制备了具有羟基和甲氧基羰氧基官能团的六元环状碳酸酯。使用由诺维信435（固定化南极假丝酵母脂肪酶B - CalB，也称为N435）和分子筛填充床组成的不同反应器配置、流速和生物催化剂负载量来评估流动反应效率。生物催化剂和分子筛的混合柱能够快速有效地去除副产物甲醇，是最有效的装置。在12小时内使用相同量的N435（20%（w/w）N435:TMP），与间歇过程（72%）相比，流动反应获得了更高的转化率（81.6%），并且抑制了不希望的二聚体和低聚物的形成。此外，产物无需额外的分离步骤即可轻松回收，生物催化剂和分子筛保持完整以便后续再生和循环使用。通过计算机模拟和实验分别评估了CalB与DMC以及初级酯交换产物单碳酸化TMP作为酰基供体的反应，以确定该酶在环状碳酸酯和其他副产物形成中的作用。结果表明DMC是优选的酰基供体，这表明TMP及其碳酸化衍生物在脂肪酶催化反应中仅作为酰基受体。随后在升高的温度下催化环化生成环状碳酸酯，而不是由酶催化。© 2016美国化学工程师学会生物技术进展，33:375 - 382，2017。
