AUTHOR=Chen Xinglin , Li Li , Chan Zhuhua , Zeng Runying , Lin Mengshi , Lin Hetong 

TITLE=One-Step Process for Environment-Friendly Preparation of Agar Oligosaccharides From Gracilaria lemaneiformis by the Action of Flammeovirga sp. OC4

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00724

DOI=10.3389/fmicb.2019.00724

ISSN=1664-302X

ABSTRACT=<p>Oligosaccharides extracted from agar <italic>Gracilaria lemaneiformis</italic> (<italic>G. lemaneiformis</italic>) have stronger physiological activities and a higher value than agar itself, but the pollution caused by the extraction process greatly restricts the sustainable use of agar. In this study, four bacterial strains with a high ability to degrade <italic>G. lemaneiformis</italic> were isolated from seawater by <italic>in situ</italic> enrichment in the deep sea. Among them, <italic>Flammeovirga</italic> sp. OC4, identified by morphological observation and its 16S rRNA sequencing (98.07% similarity to type strain JL-4 of <italic>Flammeovirga aprica</italic>), was selected. The optimum temperature and pH of crude enzyme produced by <italic>Flammeovirga</italic> sp. OC4 were 50°C and 8, respectively. More than 60% of the maximum enzyme activity remained after storage at pH 5.0–10.0 for 60 min. Both Mn<sup>2+</sup> and Ba<sup>2+</sup> could enhance the enzyme activity. A “one-step process” for preparation of oligosaccharides from <italic>G. lemaneiformis</italic> was established using <italic>Flammeovirga</italic> sp. OC4. After optimization of the Plackett–Burman (PB) design and response surface methodology (RSM), the yield of oligosaccharides was increased by 36.1% from 2.71 to 3.09 g L<sup>−1</sup> in a 250-mL fermenter with optimized parameters: 30 g L<sup>−1</sup><italic>G. lemaneiformis</italic> powder, 4.84 g L<sup>−1</sup> (NH4)<sub>2</sub>SO<sub>4</sub>, 44.8-mL working medium volume at 36.7°C, and a shaking speed of 200 × <italic>g</italic> for 42 h. The extracted oligosaccharides were identified by thin layer chromatography (TLC) and ion chromatography, which consisted of neoagarobiose, agarotriose, neoagarotetraose, agaropentaose, and neoagarohexaose. These results provided an alternative approach for environment-friendly and sustainable utilization of algae.</p>