Abstract

Marine yeasts have tremendous potential in industrial applications but have received less attention than terrestrial yeasts and marine filamentous fungi. In this study, we have screened marine yeasts for amylolytic activity and identified an amylase-producing strain PH-Gra1 isolated from sea algae. PH-Gra1 formed as a coral-red colony on yeast–peptone–dextrose (YPD) agar; the maximum radial growth was observed at 22 °C, pH 6.5 without addition of NaCl to the media. Based on the morphology and phylogenetic analyses derived from sequences of internal transcribed spacer (ITS) and a D1/D2 domain of large subunit of ribosomal DNA, PH-Gra1 was designated Sporidiobolus pararoseus. S. pararoseus is frequently isolated from marine environments and known to produce lipids, carotenoids, and several enzymes. However, its amylolytic activity, particularly the optimum conditions for enzyme activity and stability, has not been previously characterized in detail. The extracellular crude enzyme of PH-Gra1 displayed its maximum amylolytic activity at 55 °C, pH 6.5, and 0%–3.0% (w/v) NaCl under the tested conditions, and the activity increased with time over the 180-min incubation period. In addition, the crude enzyme hydrolyzed potato starch more actively than corn and wheat starch, and was stable at temperatures ranging from 15 °C to 45 °C for 2 h. This report provides a basis for additional studies of marine yeasts that will facilitate industrial applications.

摘要

海洋酵母在工业应用中具有巨大潜力，但与陆地酵母和海洋丝状真菌相比，受到的关注较少。在这项研究中，我们筛选了海洋酵母的淀粉分解活性，并鉴定了从海藻中分离出的产淀粉酶菌株 PH-Gra1。PH-Gra1 在酵母-蛋白胨-葡萄糖 (YPD) 琼脂上形成珊瑚红色菌落；在 22 °C、pH 6.5 且不向培养基中添加 NaCl 的情况下观察到最大径向生长。基于源自内转录间隔区 (ITS) 序列和核糖体 DNA 大亚基 D1/D2 结构域的形态学和系统发育分析，PH-Gra1 被命名为Sporidiobolus pararoseus。副玫瑰链球菌经常从海洋环境中分离出来，已知能产生脂质、类胡萝卜素和多种酶。然而，其淀粉分解活性，特别是酶活性和稳定性的最佳条件，以前尚未详细表征。PH-Gra1的胞外粗酶在测试条件下在55℃、pH 6.5和0%–3.0%(w/v) NaCl下表现出最大的淀粉分解活性，并且在180分钟的孵育过程中活性随着时间的推移而增加时期。此外，粗酶对马铃薯淀粉的水解活性比玉米和小麦淀粉更活跃，并且在15℃至45℃的温度范围内稳定2小时。该报告为海洋酵母的进一步研究奠定了基础，从而促进了工业应用。