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Polysaccharides from Enteromorpha prolifera (PE) are becoming increasingly popular due to its bioactivity and abundant source. Screening novel microorganisms which could secrete enzymes to degrade PE efficiently for oligosaccharides production is a promising solution to improve its application. In this study, a marine bacterium that can produce enzymes to degrade PE specifically was selected. It was identified as Alteromonas sp. A321, based on the biochemical properties and 16S rDNA gene sequencing. In order to maximize the activity of degradase for polysaccharides from E. prolifera (DPE), the effects of medium composition and culture conditions were investigated. The highest DPE production was obtained in the medium consisting of K2HPO4 0.15%, PE 0.9%, NaNO3 0.4%, NaCl 1.0% and MgSO4 0.05%. The degradase activity was enhanced from original 0.391 U/ml to 0.744 U/ml. DPE show high efficiency and substrate specificity to PE with 63.53% of reducing sugar production in the 7 h hydrolysis., (Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.)

The phenotypic and agarolytic features of an unidentified marine bacteria isolated from the southern ocean of China was studied. The strain was gram-negative, aerobic, and polarly flagellated. It was identified as the genus Alteromonas according to its morphological and physiological characterization. In solid agar, the isolate produced a diffusible agarase that caused agar softening around the colonies. An extracellular agarase was purified by the procedure of ammonium sulfate precipitation, gel filtration on Sephacryl S-100HR, and ion-exchange chromatography on diethylaminoethyl-Sepharose. The purified protein exhibited a single band on SDS-PAGE with a molecular mass of 39.5 kDa. The enzyme hydrolyzed the beta-1,4-glycosidic linkages of agar, yielding neoagarotetraose and neoagarohexaose as the main products. The optimum reaction temperature of the agarase was 35 degrees C, with a narrow range from 30 to 45 degrees C. The enzyme activity reached the maximum at pH 7.0 and in the presence of 2% NaCl. Molecular mass and degrading products showed that the agarase from Alteromonas sp. SY 37-12 was much different from those previously reported.

Abstract A β-agarase was identified from Pseudoalteromonas sp. Q30F and heterologously expressed in Bacillus subtilis WB800n. The β-agarase, Aga862 encoded by aga862 gene in an open reading frame of 1338 bp is 445 amino acids in length, and has a calculated molecular mass of 50.1 kDa and an estimated isoelectric point of 4.81. Protein sequence analysis showed that Aga862 belongs to family 16 of glycoside hydrolases (GH16) and carbohydrate-binding module family 13 (CBM13). The agarase was expressed in B. subtilis WB800n and purified by precipitation, anion exchange and gel filtration for a specific activity of 4.6 U/mg, a 27.8-fold improvement over the activity of the crude enzyme. Aga862 exhibited optimal activity at 45 °C and pH 6.5, and showed excellent pH stability with retention of over 80% relative activities after preincubation for the pH range of 3.0–10.0 at 4 °C for 3 h. The agarase exhibited a K m value of 14.15 mg/mL toward agarose and a V max of 256.41 U/mg. The mass spectrometry analysis revealed that the end products of agar degradation were neoagarotetraose and neoagarohexaose. Recombinant Aga862 has great potential for the manufacture of agaro-oligosaccharides for the non-pathogenic nature and safety of the B. subtilis WB800n. Highlights • A β-agarase Aga862 from Pseudoalteromonas sp. Q30F was expressed in B. subtilis. • After purification, the specific activity of Aga862 increased by 27.8 times. • Aga862 optimum activity was at 45 °C, pH 6.5, with excellent pH stability. • Aga862 is expected to be an industrial zymin to produce NA4 and NA6. [ABSTRACT FROM AUTHOR]