In this study, a GH26 endo-mannanase (Man26A) from an Aspergillus niger ATCC 10864 strain, with a molecular mass of 47.8 kDa, was cloned in a yBBH1 vector and expressed in Saccharomyces cerevisiae Y294 strain cells. Upon fractionation by ultra-filtration, the substrate specificity and substrate degradation pattern of the endo-mannanase (Man26A) were investigated using ivory nut linear mannan and two galactomannan substrates with varying amounts of galactosyl substitutions, guar gum and locust bean gum. Man26A exhibited substrate specificity in the order: locust bean gum ≥ ivory nut mannan > guar gum; however, the enzyme generated more manno-oligosaccharides (MOS) from the galactomannans than from linear mannan during extended periods of mannan hydrolysis. MOS with a DP of 2–4 were the major products from mannan substrate hydrolysis, while guar gum also generated higher DP length MOS. All the Man26A generated MOS significantly improved the growth (approximately 3-fold) of the probiotic bacterial strains Streptococcus thermophilus and Bacillus subtilis in M9 minimal medium. Ivory nut mannan and locust bean gum derived MOS did not influence the auto-aggregation ability of the bacteria, while the guar gum derived MOS led to a 50 % reduction in bacterial auto-aggregation. On the other hand, all the MOS significantly improved bacterial biofilm formation (approximately 3-fold). This study suggests that the prebiotic characteristics exhibited by MOS may be dependent on their primary structure, i.e. galactose substitution and DP. Furthermore, the data suggests that the enzyme-generated MOS may be useful as potent additives to dietary foods.

在本研究中，来自黑曲霉ATCC 10864 菌株的 GH26 内切甘露聚糖酶 (Man26A) ，分子量为 47.8 kDa，被克隆到 yBBH1 载体中，并在酿酒酵母中表达Y294 菌株细胞。通过超滤分级，使用象牙坚果线性甘露聚糖和两种半乳糖基取代量不同的半乳甘露聚糖底物、瓜尔胶和刺槐豆胶研究内切甘露聚糖酶 (Man26A) 的底物特异性和底物降解模式。Man26A表现出的底物特异性顺序为：刺槐豆胶≥象牙甘露聚糖>瓜尔胶；然而，在长时间的甘露聚糖水解过程中，该酶从半乳甘露聚糖中产生的甘露寡糖 (MOS) 多于线性甘露聚糖。DP 为 2-4 的 MOS 是甘露聚糖底物水解的主要产物，而瓜尔胶也产生了更高 DP 长度的 MOS。所有 Man26A 生成的 MOS 显着改善了益生菌菌株的生长（约 3 倍）M9 基本培养基中的嗜热链球菌和枯草芽孢杆菌。象牙仁甘露聚糖和刺槐豆胶衍生的 MOS 不影响细菌的自聚集能力，而瓜尔豆胶衍生的 MOS 导致细菌自聚集减少 50%。另一方面，所有 MOS 都显着改善了细菌生物膜的形成（约 3 倍）。这项研究表明，MOS 所表现出的益生元特性可能取决于它们的一级结构，即半乳糖替代和 DP。此外，数据表明酶产生的 MOS 可用作膳食食品的有效添加剂。