Expression and enzymatic characterization of a cold-adapted β-agarase from Antarctic bacterium Pseudoalteromonas sp.NJ21

An agar-degrading bacterium, designated as Pseudoalteromonas sp. NJ21, was isolated from an Antarctic sediment sample. The agarase gene aga1161 from Pseudoalteromonas sp. NJ21 consisting of a 2 382-bp coding region was cloned. The gene encodes a 793-amino acids protein and was found to possess characteristic features of the Glyco_hydro 42 family. The recombinant agarase （rAgal 161） was overexpressed in Escherichia coli and purified as a fusion protein. Enzyme activity analysis revealed that the optimum temperature and pH for the purified recombinant agarase were 30--40℃ and 8.0, respectively. rAga 1161 was found to maintain as much as 80% of its maximum activity at 10℃, which is typical of a cold- adapted enzyme. The pattern of agar hydrolysis demonstrated that the enzyme is an β-agarase, producing neoagarobiose （NA2） as the final main product. Furthermore, this work is the first proof of an agarolytic activity in Antarctic bacteria and these results indicate the potential for the Antarctic agarase as a catalyst in medicine, food and cosmetic industries.

Isolation, chemical characteristics and immunity activity of an extracellular polysaccharide EPS I isolated from Antarctic bacterium Pseudoalteromonas sp.S-15-13

A new extracelluar polysaccharide （EPS） was isolated and purified from Antarctic bacterium S-15-13, identified as Pseudoalteromonas sp. After being separated and purified by DEAE-Sephadex A-50 ionexchange and Sephadex G-100 gel chromatography, two mains fractions （EPS I and EPS Ⅱ ） were ob-tained. EPS I was composed of mannose, glucose and galactose with a molecular weight of 23kDa and EPS Ⅱ was composed of mannose only with a molecular weight of 62kDa. The effect of the polysaccharide EPS I on the cellular immune response of mice was investigated. Results demonstrated that EPS I could markedly facilitate lymphocyte proliferation, and might be a strong immunomodulator.

Activation of macrophages by an exopolysaccharide isolated from Antarctic P sychrobacter sp.B-3

An exopolysaccharide(EPS) was isolated and purified from an Antarctic psychrophilic bacterium B-3,identified as Psychrobacter sp.,and the activation of RAW264.7 cells by B-3 EPS was investigated.The results show that B-3 EPS,over a certain concentration range,promoted cell viability,nitric oxide production,tumor necrosis factor(TNF)a secretion,and phagocytic ability.Furthermore,TAK-242,an inhibitor of the toll-like receptor 4(TLR4) significantly reduced nitric oxide production by these cells after stimulation with B-3 EPS.Moreover,B-3 EPS induced p65 phosphorylation and IκBα degradation in these cells.In conclusion,B-3 EPS might have activated RAW264.7 cells by combining with TLR4 on cell surface and triggering activation of NF-κB signaling pathways,implying that this EPS could activate macrophages and regulate initial immune response.