Vitreoscilla hemoglobin promotes Salecan production by Agrobacterium sp. ZX09

Salecan is a novel exopolysaccharide produced by the strain Agrobacterium sp. 7__X09, and it is composed of only glucose monomers. The unique chemical composition and excellent physicochemical properties make Salecan a promising material for applications in coagulation, lubrication, protection against acute liver injury, and alleviating constipation. In this study, we cloned the Vitreosci/la hemoglobin gene into a broad-host-range plasmid pCM158. Without antibiotic selection, there was negligible loss of the plasmid in the host Agrobacterium sp. ZX09 after one passage of cultivation. The expression of Vitreoscilla hemoglobin was demonstrated by carbon monoxide （CO） dif- ference spectrum. The engineered strain Agrobacterium sp. ZX09 increased Salecan yield by 30%. The other physi- ological changes included its elevated respiration rate and cellular invertase activity.

索拉胶-PVA复合水凝胶的制备及其伤口促愈合性能研究

索拉胶是一种水溶性细菌胞外多糖,单一成分的索拉胶水凝胶通常机械性能较差,难以有效应用于伤口敷料领域。采用与其他聚合物共混构建具有互穿聚合物网络的水凝胶可有效改善上述情况。因此,该研究首先利用具有生物粘附特性的聚多巴胺和索拉胶间的静电作用构建第一层凝胶网络;再以聚乙烯醇为另一主要基质进行共混,通过循环冷冻-解冻法构建第二层凝胶网络,从而制备复合水凝胶。通过粘弹性能测试确定水凝胶的最佳制备条件为:索拉胶浓度4%,聚乙烯醇浓度为8%,–20℃冷冻18 h,4℃解冻6 h,冷冻-解冻循环4次。所制备的复合水凝胶内部为分布均匀,高度连续的多孔结构,平衡溶胀率达到41.6%,在5 h内能较好地保证伤口处的湿润环境;其应力、断裂伸长率、断裂能分别为0.21 MPa、117.1%、15.5 J/m。动物实验结果表明该复合水凝胶可有效促进大鼠创面愈合,有望用作伤口敷料。

β-葡聚糖在胃肠道方面的生理学功能

β-葡聚糖是一类由β-吡喃型葡萄糖基通过(1→3)、(1→4)或(1→6)糖苷键连接而成的多糖。β-葡聚糖除了具有降低胆固醇、控制血糖等功能外,在胃肠道方面还具有其他重要的生理学功能。本文详细地综述了谷物β-葡聚糖对胃排空的影响,在小肠中对营养素吸收与肠道蠕动的影响,以及在大肠中对肠道微生物生长与微生物发酵的影响,同时对酵母β-葡聚糖和索拉胶在胃肠道方面的生理学功能作了简述,并展望了细菌胞外β-葡聚糖的应用前景。