Purification and Characterization of a Novel Exo-β-Mannanase from Aeromonas sp. F-25

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Abstract
A novel exo-β-mannanase (1,4-β-D-mannan mannobiohydrolase) was isolated from the culture fluid of strain No. F-25 of Aeromonas hydrophila subspecies anaerogenes, and purified about 4,000-fold by ammonium sulfate precipitation and successive column chromatographies. The final enzyme preparation appeared to be homogeneous on polyacrylamide gel electrophoresis. The enzyme hydrolyzed the β-1,4-mannan link in polysaccharides of three or more β-1,4-linked D-mannose units. The enzyme had a molecular weight of 64,000, pI of 5.9, pH optimum of 6.0, and was stable in a pH region of 5.0 to 8.5 and at temperatures below 45°C. The Km values of the enzyme were 5.1 × 10−4 M for mannotriose, 2.4 × 10−4 M for mannotet-raose and 1.3 × 10−4 M for mannopentaose. The enzyme attacked codium and coffee mannans to give only mannobiose. Mannobiosyl- and mannotetraosyl-mannitol were hydrolyzed to produce mannobiose and mannitol, while mannobiose and mannosylmannitol were released from mannotriosylmannitol. The enzyme did not act on mannobiose, p-nitrophenyl-β-D-mannoside, konjac glucomannan, or guar gum galactomannan. Furthermore, the enzyme catalyzed a transglycosylation reaction.

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