Department of Biotechnology and Nanomedicine, SINTEF Industry, Richard Birkelands vei 3 B, 7034 Trondheim, Norway; Norwegian Biopolymer Laboratory (NOBIPOL), Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælands vei 6/8, 7491 Trondheim, Norway.
Norwegian Biopolymer Laboratory (NOBIPOL), Department of Biotechnology and Food Science, NTNU Norwegian University of Science and Technology, Sem Sælands vei 6/8, 7491 Trondheim, Norway.
Carbohydr Polym. 2024 Feb 1;325:121557. doi: 10.1016/j.carbpol.2023.121557. Epub 2023 Nov 4.
Alginates are valued in many industries, due to their versatile properties. These polysaccharides originate from brown algae (Phaeophyceae) and some bacteria of the Azotobacter and Pseudomonas genera, consisting of 1 → 4 linked β-d-mannuronic acid (M), and its C5-epimer α-l-guluronic acid (G). Several applications rely on a high G-content, which confers good gelling properties. Because of its high natural G-content (F = 0.60-0.75), the alginate from Laminaria hyperborea (LH) has sustained a thriving industry in Norway. Alginates from other sources can be upgraded with mannuronan C-5 epimerases that convert M to G, and this has been demonstrated in many studies, but not applied in the seaweed industry. The present study demonstrates epimerisation directly in the process of alginate extraction from cultivated Saccharina latissima (SL) and Alaria esculenta (AE), and the lamina of LH. Unlike conventional epimerisation, which comprises multiple steps, this in-process protocol can decrease the time and costs necessary for alginate upgrading. In-process epimerisation with AlgE1 enzyme enhanced G-content and hydrogel strength in all examined species, with the greatest effect on SL (F from 0.44 to 0.76, hydrogel Young's modulus from 22 to 34 kPa). As proof of concept, an upscaled in-process epimerisation of alginate from fresh SL was successfully demonstrated.
褐藻胶因其多功能特性而在许多行业中具有价值。这些多糖来源于褐藻（Phaeophyceae）和一些固氮菌属（Azotobacter）和假单胞菌属（Pseudomonas）的细菌，由 1→4 键合的β-d-甘露糖醛酸（M）及其 C5 差向异构体α-l-古洛糖醛酸（G）组成。许多应用依赖于高 G 含量，这赋予其良好的凝胶性能。由于其天然 G 含量高（F=0.60-0.75），来自长叶巨藻（Laminaria hyperborea）（LH）的褐藻胶在挪威一直拥有繁荣的产业。其他来源的褐藻胶可以通过甘露聚糖 C-5 差向异构酶进行升级，将 M 转化为 G，许多研究已经证明了这一点，但尚未在海藻工业中应用。本研究直接在从培养的裙带菜（Saccharina latissima）（SL）和海蒿子（Alaria esculenta）（AE）以及 LH 叶片中提取褐藻胶的过程中进行了差向异构化，与包括多个步骤的常规差向异构化不同，该过程中的方法可以减少褐藻胶升级所需的时间和成本。AlgE1 酶的过程中差向异构化提高了所有检测物种的 G 含量和水凝胶强度，对 SL 的效果最大（F 从 0.44 增加到 0.76，水凝胶杨氏模量从 22 增加到 34 kPa）。作为概念验证，成功地展示了新鲜 SL 褐藻胶的放大过程中差向异构化。
