Samaratunga Ashani, Kudina Olena, Nahar Nurun, Zakharchenko Andrey, Minko Sergiy, Voronov Andriy, Pryor Scott W
Department of Agricultural and Biosystems Engineering, North Dakota State University, Fargo, ND, 58108-6050, USA.
Appl Biochem Biotechnol. 2015 Jun;176(4):1114-30. doi: 10.1007/s12010-015-1633-z. Epub 2015 May 3.
Production costs of cellulosic biofuels can be lowered if cellulases are recovered and reused using particulate carriers that can be extracted after biomass hydrolysis. Such enzyme recovery was recently demonstrated using enzymogel nanoparticles with grafted polymer brushes loaded with cellulases. In this work, cellulase (NS50013) and β-glucosidase (Novozyme 188) were immobilized on enzymogels made of poly(acrylic acid) polymer brushes grafted to the surface of silica nanoparticles. Response surface methodology was used to model effects of pH and temperature on hydrolysis and recovery of free and attached enzymes. Hydrolysis yields using both enzymogels and free cellulase and β-glucosidase were highest at the maximum temperature tested, 50 °C. The optimal pH for cellulase enzymogels and free enzyme was 5.0 and 4.4, respectively, while both free β-glucosidase and enzymogels had an optimal pH near 4.4. Highest hydrolysis sugar concentrations with cellulase and β-glucosidase enzymogels were 69 and 53 % of those with free enzymes, respectively. Enzyme recovery using enzymogels decreased with increasing pH, but cellulase recovery remained greater than 88 % throughout the operating range of pH values less than 5.0 and was greater than 95 % at pH values below 4.3. Recovery of β-glucosidase enzymogels was not affected by temperature and had little impact on cellulase recovery.
如果使用在生物质水解后能够提取的颗粒载体来回收和再利用纤维素酶，纤维素生物燃料的生产成本就能降低。最近，利用负载有纤维素酶的接枝聚合物刷的酶凝胶纳米颗粒证明了这种酶的回收。在这项工作中，将纤维素酶（NS50013）和β-葡萄糖苷酶（诺维信188）固定在由接枝到二氧化硅纳米颗粒表面的聚丙烯酸聚合物刷制成的酶凝胶上。采用响应面法对pH值和温度对游离酶和固定化酶的水解及回收的影响进行建模。使用酶凝胶以及游离纤维素酶和β-葡萄糖苷酶时，在所测试的最高温度50℃下，水解产率最高。纤维素酶酶凝胶和游离酶的最佳pH值分别为5.0和4.4，而游离β-葡萄糖苷酶和酶凝胶的最佳pH值均接近4.4。纤维素酶和β-葡萄糖苷酶酶凝胶的最高水解糖浓度分别为游离酶的69%和53%。使用酶凝胶的酶回收率随pH值升高而降低，但在pH值小于5.0的整个操作范围内，纤维素酶回收率仍大于88%，在pH值低于4.3时大于95%。β-葡萄糖苷酶酶凝胶的回收率不受温度影响，对纤维素酶回收率影响很小。
