Structural characterisation and anti-ageing activity of extracellular polysaccharide from a strain of Lachnum sp.

A homogeneous extracellular polysaccharide of Lachnum YM261(LEPS-1) with a molecular weight of 21670 Da was characterised. According to HPGPC, IR, periodate oxidation and Smith degradation, GC-MS and ¹H NMR analysis, the results indicated that LEPS-1 was a glucan linked by the β-(1 → 3)-d-pyran glycosidic bond. The effect of LEPS-1 on anti-ageing in d-gal model mice was also studied. It was found that LEPS-1 significantly increased the activities of antioxidant enzymes (i.e. SOD superoxide dismutase, CAT catalase, GSH-PX glutathione peroxidase) and decreased malondialdehyde (MDA) content in liver, brain and serum of d-gal model mice. These results showed that LEPS-1 had a strong anti-ageing activity.     

Effects of Lycium barbarum extract on production and immunomodulatory activity of the extracellular polysaccharopeptides from submerged fermentation culture of Coriolus versicolor

Polysaccharopeptides (PSPs) from Coriolus versicolor have been used as immunomodulatory and anticancer agents. However, most studies have concentrated on the mycelial PSPs and not those in the fermented broth. On the other hand, Lycium barbarum fruit has been used as a traditional Chinese herbal medicine for two millennia. Its extract contains various nutrients, minerals, and also polysaccharide–protein complexes, which are proven to be bioactive. Herein we report the effects of L. barbarum fruit extract on the mycelial growth and extracellular PSP (ePSP) production of C. versicolor LH1 by using a submerged fermentation process in 20 l fermenters. Fermentation production of C. versicolor biomass and its ePSP were augmented in the presence of L. barbarum extract. The ePSP such obtained differs from those obtained with normal culture medium in terms of simple sugar composition and protein content but shows similar overall chemical structures as analyzed by Fourier transformed infrared spectroscopy. Moreover, the ePSP from C. versicolor cultured with supplementary L. barbarum extract exhibits significant immunomodulatory activity as judged by its effects on the production of nitric oxide and several cytokines by murine RAW264.7 macrophages.     

Streptomyces lavendulae X33海藻糖合酶基因克隆及酶学特性

目的：对菌株Bacillus sp. B110的胞内麦芽糖淀粉酶BMAL进行基因克隆、异源表达、纯化及酶学性质研究,为后期开发新的淀粉加工用酶打下基础。方法：使用PCR技术对Bacillus sp. B110的胞内麦芽糖淀粉酶bmal基因序列进行全长克隆,异源表达,使用Ni²⁺-NTA进行纯化,再对其酶学特性进行测定,使用序列分析工具BioEdit、MEGA等对其氨基酸序列进行分析,使用AlphaFold2对其三级结构进行预测分析。结果：BMAL基因全长1770 bp,编码一个589氨基酸残基的蛋白。重组酶rBMAL经Ni²⁺-NTA亲和层析纯化后,SDS-PAGE电泳结果显示其分子量大小为63 kDa。氨基酸序列分析和三维建模表明BMAL与来源于B.subtilis 168和B.subtilis SUH4-2的麦芽糖淀粉酶有较高的一致性,且BMAL具有一个麦芽糖淀粉酶所独有的N端结构域以及由Asp328-Glu357-Asp424三个氨基酸残基所构成的催化中心。重组酶rBMAL最适反应温度为45 ℃,最适反应pH为6.0。重组酶rBMAL在30 ℃条件下保藏7 h残留酶活为60%,但在60 ℃条件下保藏2 h残留酶活力下降98%,说明BMAL对热敏感。重组酶rBMAL在4 ℃,pH7.0~9.5保藏12 h活性稳定。当存在1 mmol/L的金属离子Mg²⁺时,重组酶rBMAL活力提高36%,而Ni²⁺、Fe³⁺、Co²⁺、Cu²⁺、Zn²⁺、Al³⁺、Ca²⁺对重组酶rBMAL有抑制作用,酶活力减少85%~48%。有机溶剂和化学试剂甲醇、乙醇、丙酮、异腈、EDTA和SDS对重组酶rBMAL有较强的抑制作用,酶活力减少至32.3%~64.8%。底物特异性实验结果证实BMAL最适底物为环精糊。结论：Bacillus sp. B110的胞内麦芽糖淀粉酶BMAL具有良好的催化特性和pH稳定性,在面包烘焙工业上具有潜在的应用价值。