Background: Laminarin is a potential biomass feedstock for the production of glucose, which is the most preferable fermentable sugar in many microorganisms by which it can be converted to biofuels and bio-based chemicals. Also, laminarin is a good resource as functional materials because it consists of β-1,3-glucosidic linkages in its backbone and β-1,6-glucosidic linkages in its branches so that its oligosaccharides driven from laminarin have a variety of biological activities. It is industrially important to be able to produce laminarioligosaccharides as well as glucose from laminarin by a single enzyme because the enzyme cost accounts for a large part of bio-based products. In this study, we investigated the industrial applicability of Bgl1B, a unique β-glucosidase from Saccharophagus degradans 2-40T, belonging to the glycoside hydrolase family 1 (GH1) by characterizing its activity of hydrolyzing laminarin under various conditions. Results: Bgl1B was cloned and overexpressed in Escherichia coli from S. degradans 2-40T, and its enzymatic activity was characterized. Similar to most of β-glucosidases in GH1, Bgl1B was able to hydrolyze a variety of disaccharides having different β-linkages, such as laminaribiose, cellobiose, gentiobiose, lactose, and agarobiose, by cleaving β-1,3-, β-1,4-, and β-1,6-glycosidic linkages. However, Bgl1B showed the highest specific activity toward laminaribiose with a β-1,3-glycosidic linkage. In addition, it was able to hydrolyze laminarin, one of the major polysaccharides in brown macroalgae, into glucose with a conversion yield of 75% of theoretical maximum. Bgl1B also showed transglycosylation activity by producing oligosaccharides from laminarin and laminaribiose under a high mass ratio of substrate to enzyme. Furthermore, Bgl1B was found to be psychrophilic, exhibiting relative activity of 59-85% in the low-temperature range of 2-20 °C. Conclusions: Bgl1B can directly hydrolyze laminarin into glucose with a high conversion yield without leaving any oligosaccharides. Bgl1B can exhibit high enzymatic activity in a broad range of low temperatures (2-20 °C), which is advantageous for establishing energy-efficient bioprocesses. In addition, under high substrate to enzyme ratios, Bgl1B can produce high-value laminarioligosaccharides via its transglycosylation activity. These results show that Bgl1B can be an industrially important enzyme for the production of biofuels and bio-based chemicals from brown macroalgae.
Bibliographical noteFunding Information:
We want to acknowledge grant support from the National Research Founda‑ tion of Korea (NRF‑2017R1A2B2005628). This work was performed at the Korea University Food Safety Hall for the Institute of Biomedical Science and Food Safety.
© 2018 The Author(s).
- Brown macroalgae
ASJC Scopus subject areas
- Applied Microbiology and Biotechnology
- Renewable Energy, Sustainability and the Environment
- Management, Monitoring, Policy and Law