Misson Mailin, Dai Sheng, Jin Bo, Chen Bing H, Zhang Hu
School of Chemical Engineering, University of Adelaide, Adelaide SA 5000, Australia; Biotechnology Research Institute, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia.
School of Chemical Engineering, University of Adelaide, Adelaide SA 5000, Australia.
J Biotechnol. 2016 Mar 20;222:56-64. doi: 10.1016/j.jbiotec.2016.02.014. Epub 2016 Feb 10.
The nanoenvironment of nanobiocatalysts, such as local hydrophobicity, pH and charge density, plays a significant role in optimizing the enzymatic selectivity and specificity. In this study, Kluyveromyces lactis β-galactosidase (Gal) was assembled onto polystyrene nanofibers (PSNFs) to form PSNF-Gal nanobiocatalysts. We proposed that local hydrophobicity on the nanofiber surface could expel water molecules so that the transgalactosylation would be preferable over hydrolysis during the bioconversion of lactose, thus improve the galacto-oligosaccharides (GOS) yield. PSNFs were fabricated by electro-spinning and the operational parameters were optimized to obtain the nanofibers with uniform size and ordered alignment. The resulting nanofibers were functionalized for enzyme immobilization through a chemical oxidation method. The functionalized PSNF improved the enzyme adsorption capacity up to 3100 mg/g nanofiber as well as enhanced the enzyme stability with 80% of its original activity. Importantly, the functionalized PSNF-Gal significantly improved the GOS yield and the production rate was up to 110 g/l/h in comparison with 37 g/l/h by free β-galactosidase. Our research findings demonstrate that the localized nanoenvironment of the PSNF-Gal nanobiocatalysts favour transgalactosylation over hydrolysis in lactose bioconversion.
纳米生物催化剂的纳米环境，如局部疏水性、pH值和电荷密度，在优化酶的选择性和特异性方面发挥着重要作用。在本研究中，将乳酸克鲁维酵母β-半乳糖苷酶（Gal）组装到聚苯乙烯纳米纤维（PSNFs）上，形成PSNF-Gal纳米生物催化剂。我们提出，纳米纤维表面的局部疏水性可以排出水分子，从而在乳糖的生物转化过程中，转半乳糖基化比水解更占优势，进而提高低聚半乳糖（GOS）的产量。通过静电纺丝制备PSNFs，并优化操作参数以获得尺寸均匀且排列有序的纳米纤维。通过化学氧化法对所得纳米纤维进行功能化处理以固定酶。功能化的PSNF将酶吸附容量提高到3100 mg/g纳米纤维，同时增强了酶的稳定性，保留了80%的原始活性。重要的是，功能化的PSNF-Gal显著提高了GOS的产量，与游离β-半乳糖苷酶的37 g/l/h相比，生产率高达110 g/l/h。我们的研究结果表明，PSNF-Gal纳米生物催化剂的局部纳米环境在乳糖生物转化中有利于转半乳糖基化而非水解。
