Marine College, Shandong University, Weihai 264209, China.
State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China.
Mar Drugs. 2022 Apr 4;20(4):254. doi: 10.3390/md20040254.
Alginate is the main component of brown algae, which is an important primary production in marine ecosystems and represents a huge marine biomass. The efficient utilization of alginate depends on alginate lyases to catalyze the degradation, and remains to be further explored. In this study, 354 strains were isolated from the gut of adult abalones, which mainly feed on brown algae. Among them, 100 alginate-degrading strains were gained and the majority belonged to the , followed by the and . A marine bacterium, sp. B2Z047, had the strongest degradation ability of alginate with the largest degradation circle and the highest enzyme activity. The optimal alginate lyase production medium of strain B2Z047 was determined as 1.1% sodium alginate, 0.3% yeast extract, 1% NaCl, and 0.1% MgSO in artificial seawater (pH 7.0). Cells of strain B2Z047 were Gram-stain-negative, aerobic, motile by flagella, short rod-shaped, and approximately 0.7-0.9 µm width and 1.2-1.9 µm length. The optimal growth conditions were determined to be at 30 °C, pH 7.0-8.0, and in 3% (/) NaCl. A total of 12 potential alginate lyase genes were identified through whole genome sequencing and prediction, which belonged to polysaccharide lyase family 6, 7, 17, and 38 (PL6, PL7, PL17, and PL38, respectively). Furthermore, the degradation products of nine alginate lyases were detected, among which Aly38A was the first alginate lyase belonging to the PL38 family that has been found to degrade alginate. The combination of alginate lyases functioning in the alginate-degrading process was further demonstrated by the growth curve and alginate lyase production of strain B2Z047 cultivated with or without sodium alginate, as well as the content changes of total sugar and reducing sugar and the transcript levels of alginate lyase genes. A simplified model was proposed to explain the alginate utilization process of sp. B2Z047.
褐藻中的主要成分是褐藻胶，它是海洋生态系统中重要的初级生产力，代表着巨大的海洋生物质。褐藻胶的有效利用依赖于褐藻胶裂解酶来催化降解，这仍然需要进一步探索。在这项研究中，从主要以褐藻为食的成年鲍鱼肠道中分离出 354 株菌株。其中，获得了 100 株褐藻降解菌株，其中大多数属于 ，其次是 和 。一种海洋细菌 ，B2Z047，具有最强的褐藻胶降解能力，具有最大的降解圈和最高的酶活性。确定菌株 B2Z047 的最佳褐藻胶裂解酶生产培养基为人工海水中的 1.1%褐藻酸钠、0.3%酵母提取物、1%NaCl 和 0.1%MgSO（pH7.0）。B2Z047 菌株的细胞革兰氏阴性，需氧，通过鞭毛运动，短杆状，约 0.7-0.9 µm 宽和 1.2-1.9 µm 长。最佳生长条件确定为 30°C、pH7.0-8.0 和 3%（/）NaCl。通过全基因组测序和预测，共鉴定出 12 种潜在的褐藻胶裂解酶基因，它们属于多糖裂解酶家族 6、7、17 和 38（PL6、PL7、PL17 和 PL38）。此外，检测到 9 种褐藻胶裂解酶的降解产物，其中 Aly38A 是第一个属于 PL38 家族的褐藻胶裂解酶，已被发现可降解褐藻胶。通过 B2Z047 菌株在有无褐藻酸钠培养时的生长曲线和褐藻胶裂解酶产生、总糖和还原糖含量变化以及褐藻胶裂解酶基因的转录水平，进一步证明了褐藻胶降解过程中褐藻胶裂解酶的组合作用。提出了一个简化的模型来解释 B2Z047 对褐藻的利用过程。
