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Ce3+-induced exopolysaccharide production by Bradyrhizobium sp. MAFF211645

Paper ID Volume ID Publish Year Pages File Format Full-Text
21053 43204 2011 7 PDF Available
Title
Ce3+-induced exopolysaccharide production by Bradyrhizobium sp. MAFF211645
Abstract

Ce3+, a rare earth element (REE), has been widely used in high-technology industries. Despite the importance of Ce3+ in the fields of chemistry and physics, the role of Ce3+ in biology has been ignored. To investigate physiological effects of Ce3+ on microorganisms, we screened microorganisms that showed peculiar growth in the presence of Ce3+. We isolated a free-living soil bacterium that produced exopolysaccharide (EPS) around its colonies on 1/100 nutrient agar with 30 μM CeCl3 or 1.0% d-mannitol. The bacterium was identified as Bradyrhizobium sp. by morphological, biochemical, and physiological tests as well as 16S rDNA sequence analysis. La3+, Pr3+, and Nd3+ also induced EPS production in large quantities, while Sm3+ did in small amounts. However, other heavier REEs from Eu3+ to Lu3+, and metals such as Na+, Al3+, K+, Ca2+, V3+, Cr3+, Co2+, Ni2+, Sr2+, Ba2+, and Pb2+ did not induce EPS production. The mean molecular weight of EPS was estimated to be approximately 1 × 106 by Sepharose CL-4B column chromatography. TLC revealed that EPS was composed of l-rhamnose. Quantitative analysis of alditol acetate derivatives of acid hydrolyzate of EPS by GLC revealed that EPS was composed of more than 95% l-rhamnose, indicating that this EPS was a rhamnan. The spectrum of FT-IR of the rhamnan demonstrated that l-rhamnose residues in the rhamnan were α-linked. GC/MS analysis of methylated alditol acetate derivatives of the rhamnan demonstrated that it was composed of main chain α-(1→4)-linked l-rhamnopyranosyl residues. From spectral analyses of 1H-NMR and FT-IR, EPS produced in the presence of 1.0% d-mannitol was found to be structurally similar to rhamnans.

Keywords
Bradyrhizobium; Exopolysaccharide; Light rare earth element; Ce3+; d-Mannitol; l-Rhamnose; Rhamnan
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Ce3+-induced exopolysaccharide production by Bradyrhizobium sp. MAFF211645
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Bioscience and Bioengineering - Volume 111, Issue 2, February 2011, Pages 146–152
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us