Journal
FRONTIERS IN MICROBIOLOGY
Volume 9, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fmicb.2018.02894
Keywords
alginate lyase; Microbulbifer; heterologous expression; extracellular secretion; thermal stability; poly-guluronic acid preference
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Funding
- Public Science and Technology Research Funds Projects of Ocean [201505022]
- Shandong Natural Science Fund [ZR2017MD006]
- Shandong Science and Technology Development Project [2017YYSP003, 2014GHY115037]
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Alginate lyases play an important role in preparation of alginate oligosaccharides. Although a large number of alginate lyases have been characterized, reports on directional preparation of alginate oligosaccharides by alginate lyases are still rather less. Here, a gene alyM encoding a new alginate lyase AlyM was cloned from Microbulbifer sp. Q7 and expressed in Escherichia coll. AlyM exhibited the maximumactivity at pH 7.0 and 55 degrees C and showed special preference to poly-guluronic acid (polyG). Glycine promoted the extracellular secretion of AlyM by 3.6 times. PBS and glycerol significantly improved the thermal stability of AlyM, the enzyme activity remained 75 and 78% after heat-treatment at 45 degrees C for 2 h, respectively. ESI-MS analysis suggested that AlyM mainly produced oligosaccharides with degrees of polymerization (DP) of 2-5. The results of H-1-NMR showed that guluronic acid (G) occupied the reducing end of the end products, indicating that AlyM preferred to degrade the glycosidic bond at the G-X linkage. HPLC analysis showed that the hydrolysis products with a lower degree of polymerization contained more G. Therefore, AlyM shows good potential to produce alginate oligosaccharides with specific M/G ratio and molecular weights.
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