Title: Characterization of a thermostable κ‐carrageenase from a hot spring bacterium and plant protection activity of the oligosaccharide enzymolysis product

Abstract

Abstract Background Seaweed oligosaccharides are environmentally‐friendly natural products and their use for disease control in sustainable agriculture is extremely promising. Enzymatic digestion to prepare seaweed oligosaccharides has drawn considerable interest. However, the study of enzymatically degraded products of carrageenan is still in its infancy compared with that of other hydrocolloids such as agar and alginate. To prepare degraded carrageenan on a commercial scale, it is necessary to select superior producer bacterial strains to improve the yield and thermostability of carrageenases. Results The carrageenan‐degrading bacterium Bacillus sp. HT19 was isolated from sediment of a hot spring in Indonesia, and a κ‐carrageenase with high activity was purified from the culture supernatant. The purified enzyme, named Car19, had maximum activity (538 U mg ⁻¹ ) at 60 °C and pH 7.0. Notably, the enzyme retained >90% of its initial activity after incubation at 60 °C for 24 h. The Ca ²⁺ obviously improved the thermostability of Car19 at 70 °C. The K _m and V _max values of purified Car19 were 0.061 mg mL ⁻¹ and 115.13 U mg ⁻¹ , respectively, with κ‐carrageenan as substrate. Thin‐layer chromatography and electrospray ionization mass‐spectrometry analysis of hydrolysates indicated that the enzyme exolytically depolymerized κ‐carrageenan tomore » neo‐carrabiose. The hydrolysate enhanced the resistance of cucumber to cucumber mosaic virus and increased the activity of antioxidant enzymes in infected plants. Conclusion To our knowledge, Car19 is the most thermostable κ‐carrageenase reported so far. Its high optimal reaction temperature and thermostability, and unitary hydrolysate constituent, makes Car19 a promising candidate for the preparation of carrageenan oligosaccharides with plant protection activity. © 2018 Society of Chemical Industry« less

Authors:

Li, Jiang  ^[1];

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Pan, Aihong ^[2]; Xie, Maisheng ^[1]; Zhang, Pingping ^[3]; Gu, Xiaoqian ^[1]

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+ Show Author Affiliations

1. Key Laboratory of Marine Bioactive Substances, The First Institute of Oceanography State Oceanic Administration Qingdao P. R. China
2. College of Chemical Engineering Qingdao University of Science and Technology Qingdao P. R. China
3. College of Biological Science and Engineering Hebei University of Science and Technology Shijiazhuang P. R. China

Publication Date:

Tue Oct 30 00:00:00 EDT 2018

Sponsoring Org.:

USDOE

OSTI Identifier:

1479842

Resource Type:

Publisher's Accepted Manuscript

Journal Name:

Journal of the Science of Food and Agriculture

Additional Journal Information:

Journal Name: Journal of the Science of Food and Agriculture Journal Volume: 99 Journal Issue: 4; Journal ID: ISSN 0022-5142

Publisher:

Wiley Blackwell (John Wiley & Sons)

Country of Publication:

United Kingdom

Language:

English