Department of Biology, University of Naples Federico II, via Cinthia, 80126, Naples, Italy.
World J Microbiol Biotechnol. 2019 Jan 30;35(2):32. doi: 10.1007/s11274-019-2591-3.
Extremophilic microorganisms are valuable sources of enzymes for various industrial applications. In fact, given their optimal catalytic activity and operational stability under harsh physical and chemical conditions, they represent a suitable alternative to their mesophilic counterparts. For instance, extremophilic enzymes are important to foster the switch from fossil-based to lignocellulose-based industrial processes. Indeed, more stable enzymes are needed, because the conversion of the lignocellulosic biomass to a wide palette of value-added products requires extreme chemo-physical pre-treatments. Galactomannans are part of the hemicellulose fraction in lignocellulosic biomass. They are heteropolymers constituted by a β-1,4-linked mannan backbone substituted with side chains of α-1,6-linked galactose residues. Therefore, the joint action of different hydrolytic enzymes (i.e. β-mannanase, β-mannosidase and α-galactosidase) is needed to accomplish their complete hydrolysis. So far, numerous galactomannan-degrading enzymes have been isolated and characterized from extremophilic microorganisms. Besides applications in biorefinery, these biocatalysts are also useful to improve the quality (i.e. digestibility and prebiotic properties) of food and feed as well as in paper industries to aid the pulp bleaching process. In this review, an overview about the structure, function and applications of galactomannans is provided. Moreover, a survey of (hyper)-thermophilic galactomannans-degrading enzymes, mainly characterized in the last decade, has been carried out. These extremozymes are described in the light of their biotechnological application in industrial processes requiring harsh conditions.
极端微生物是各种工业应用中酶的有价值来源。事实上，鉴于它们在恶劣的物理和化学条件下具有最佳的催化活性和操作稳定性，它们是嗜温酶的合适替代品。例如，极端微生物酶对于促进从基于化石的工业过程向基于木质纤维素的工业过程的转变至关重要。事实上，需要更稳定的酶，因为将木质纤维素生物质转化为广泛的增值产品需要极端的化学物理预处理。半乳甘露聚糖是木质纤维素生物质中半纤维素部分的一部分。它们是由β-1,4 键合的甘露聚糖主链与α-1,6 键合的半乳糖残基侧链组成的杂多糖。因此，需要不同水解酶（即β-甘露聚糖酶、β-甘露糖苷酶和α-半乳糖苷酶）的共同作用来完成它们的完全水解。迄今为止，已经从极端微生物中分离和鉴定了许多半乳甘露聚糖降解酶。除了在生物炼制中的应用外，这些生物催化剂还有助于提高食品和饲料的质量（即消化率和益生元特性）以及造纸工业中纸浆漂白过程的质量。在这篇综述中，提供了对半乳甘露聚糖的结构、功能和应用的概述。此外，还对（超）嗜热半乳甘露聚糖降解酶进行了调查，这些酶主要是在过去十年中得到了表征。这些极端酶根据它们在需要苛刻条件的工业过程中的生物技术应用进行了描述。
