Abstract

The potential applications of β-mannanase in bioenergy, biorefinery, detergent, fodder, food processing, oil and gas, pharmaceutical, pulp and paper and textile industries, and the high cost of commercially available enzyme have attracted considerable research efforts to identify potent microbial strains for cost-effective production of this enzyme. The advantage of microbial biocatalyst is that the crude enzyme can be used directly in bioprocessing instead of the purified enzyme. In this study, β-mannanase was extracted from a novel Streptomyces sp. Alg-S25 (GenBank accession no. MK494177) and immobilized onto chitosan nanoparticles using glutaraldehyde as a crosslinker. The covalent binding of β-mannanase onto chitosan nanoparticles was confirmed by Fourier-transform infrared spectroscopy. The functionalized chitosan nanoparticles retained 83.6% ± 3.46% of β-mannanase activity. Free and immobilized β-mannanase of this novel Streptomyces sp. Alg-S25 displayed maximal activities at pH 7.5 and at temperature 50 °C and 55 °C, respectively. Immobilized β-mannanase exhibited higher values of activation energy (47.4 kJ/mol), enthalpy (44.9 kJ/mol) and entropy (–73.5 J/mol/K) of catalysis compared to the free enzyme. The substrate-specific kinetic analysis suggested that the immobilized β-mannanase had a strong affinity toward locust bean galactomannan by showing a low K _m (4.94 mg/mL) and a high V _max (93.5 U/mg-protein) values. Furthermore, the immobilized β-mannanase was not affected by 2% NaCl and retained 81.2% of the maximal activity after 10 cycles of successive reuse. These results indicate the potential of chitosan nanoparticle-immobilized β-mannanase for sustainable and cost-effective bioprocessing of mannan-containing agricultural, forest, seaweed and industrial wastes.

摘要

β-甘露聚糖酶在生物能源，生物炼制，洗涤剂，饲料，食品加工，石油和天然气，制药，纸浆和造纸以及纺织工业中的潜在应用以及高价商业化酶已吸引了相当多的研究工作，以鉴定有效的微生物菌株以经济有效的方式生产这种酶。微生物生物催化剂的优点是粗酶可以代替纯化酶直接用于生物加工。在这项研究中，β-甘露聚糖酶是从新型链霉菌中提取的sp。使用戊二醛作为交联剂将Alg-S25（GenBank登录号MK494177）固定在壳聚糖纳米颗粒上。β-甘露聚糖酶与壳聚糖纳米颗粒的共价结合通过傅里叶变换红外光谱法得以证实。功能化的壳聚糖纳米颗粒保留β-甘露聚糖酶活性的83.6％±3.46％。游离和固定化的新型链霉菌的β-甘露聚糖酶sp。Alg-S25分别在pH 7.5和50°C和55°C下显示出最大活性。与游离酶相比，固定化的β-甘露聚糖酶具有更高的活化能（47.4 kJ / mol），焓（44.9 kJ / mol）和熵（–73.5 J / mol / K）。底物特异性动力学分析表明，固定化的β-甘露聚糖酶对刺槐豆半乳甘露聚糖具有很强的亲和力，表现出低K _m（4.94 mg / mL）和高V _max。（93.5 U / mg-蛋白质）值。此外，固定的β-甘露聚糖酶不受2％NaCl的影响，并且在连续使用10个循环后仍保留了81.2％的最大活性。这些结果表明，固定有壳聚糖纳米颗粒的β-甘露聚糖酶具有潜在的可持续性和成本效益的生物处理含甘露的农业，森林，海藻和工业废物的能力。