Influence of a biopolymer admixture on corrosion behaviour of steel rebars in concrete

Among the multitude of concrete structure pathologies, corrosion of rebars is one of the most important problems of concrete durability. In the context of sustainable development, it appears of primary importance to develop new means to protect the rebars against corrosion. This study aims to develop a new eco‐friendly and corrosion‐inhibiting admixture based on EPS 180 exopolysaccharides, biopolymers used in coatings already studied for the corrosion inhibition on steel in seawater. C15 rebars embedded in CEMI and CEMV cement paste containing EPS 180 were immersed in natural seawater and their electrochemical behaviour was studied using open circuit potential measurements and electrochemical impedance spectroscopy. These tests highlight the decrease of the cathodic reaction kinetics due to the EPS 180 action at the rebars surface, and the absence of effect on the passive layer. Capillary imbibition tests carried out on cement paste and mortars showed that although limiting the imbibition kinetics for cement pastes, the EPS 180 did not influence the water imbibition of mortars. Tests comparing capillary imbibition of soaked cement pastes and mortars with EPS 180 solution and the same samples containing the EPS 180 admixture highlight that the corrosion inhibition induced by EPS 180 admixture is more due to the modification of the cement – rebars interface than to the clogging of the cement porous network.     

乳酸菌胞外多糖硒化修饰及其抗氧化活性研究

探讨了乳酸菌胞外多糖硒化修饰的最佳工艺条件,以及硒化胞外多糖的抗氧化活性。通过单因素试验确定反应温度、反应时间、硒化剂添加量的取值范围,再用响应面设计法确定最佳硒化修饰条件。试验结果表明:反应温度、反应时间、硒化剂添加量显著影响乳酸菌胞外多糖硒化的程度,当反应温度50℃、反应时间13.5h、硒化剂添加量0.55mg时硒含量和硒转化率达到最大值。在此条件下,所得硒多糖硒含量169.228μg/g,硒转化率32.37%;硒化后的多糖总抗氧化能力及对羟自由基的清除能力显著增强,而对超氧阴离子自由基的清除能力变化不大。     

液体发酵条件对灵芝菌体形态及胞外多糖活性的影响

作者主要研究灵芝在液体发酵过程中,发酵时间、初始p H值、培养温度等发酵条件对灵芝菌体形态、胞外多糖产量及多糖抗肿瘤活性的影响,其目的在于通过调控发酵条件获得高活性、高产量的灵芝多糖。依据灵芝菌球直径的大小,所有菌球被分为小型、中型和大型菌球,结果表明,发酵过程中菌体形态以中型菌球为主,在中小型菌球比例较高时有利于胞外多糖的合成,并且小型菌球比例大于大型菌球时,发酵液中多糖含量较高;在比较不同发酵条件下获得的胞外多糖对肿瘤细胞抑制作用时发现,p H 4.0和30℃条件下获得的多糖对小鼠肝癌细胞Hepa 1-6和人乳腺癌细胞MDA-MB-231具有更高的抑制作用。     

灵芝菌在茶培养基中驯化的实验研究

研究了灵芝菌经过低档绿茶萘汁、茶粉多次驯化后，平板培养时菌丝增殖速率和摇瓶发酵时菌体生物量与胞外粗多糖（EPS）的变化情况。实验结果表明，驯化种在茶汁平板和普通平板上，菌丝平均增殖速率分别提高了30．7％、8．0％；驯化种在茶培养基中发酵时，最大菌体生物量和胞外粗多糖产量分别提高了119．87％、69．39％。显然，驯化种发生了部分遗传特性良性改变。     

产胞外多糖泰山羊肚菌液体培养条件的优化

对泰山羊肚菌产胞外多糖 (exopolysaccharides,EPS)的液体培养基组成和发酵条件进行了优化 ,最适碳源是葡萄糖 ,最适氮源是NH4NO3 。正交试验确定最佳培养基组成为麸皮 2 0 0 g/L ,葡萄糖 30 g/L ,NH4NO3 1g/L ,KH2 PO42 g/L ,MgSO4·7H2 O 1 5 g/L。最佳发酵条件为 2 5℃ ,起始 pH值 6 5 ,装液量 10 0mL/瓶 ,接种量10 % ,摇床转速 2 0 0r/min ,发酵时间 4d。在此条件下 ,其胞外多糖含量 (2 135 4 4 1mg/L)比对照(14 5 4 6 39mg/L)提高了 4 6 8%。     

内蒙古酸马奶中植物乳植杆菌NM18胞外多糖的结构特征

胞外多糖（Exopolysaccharides,EPS）是具有不同糖残基的高分子聚合物,其在医药、食品、环境等不同领域都有广泛应用。该研究对植物乳植杆菌NM18所产胞外多糖采用乙醇沉淀、阴离子交换法和凝胶过滤层析法进行纯化得到6种组分（EPS-1A、EPS-1B、EPS-2、EPS-3、EPS-4和EPS-5）,并对其一级结构进行鉴定。组分EPS-1A、EPS-1B、EPS-2均由甘露糖、葡萄糖和半乳糖组成;组分EPS-3由甘露糖、葡萄糖、半乳糖、鼠李糖、岩藻糖和N-乙酰葡萄糖胺组成;组分EPS-4由甘露糖、葡萄糖、半乳糖、N-乙酰葡萄糖胺组成;组分EPS-5由甘露糖,半乳糖和N-乙酰葡萄糖胺组成,含有微量的岩藻糖及阿洛糖。组分EPS-1A、EPS-1B和EPS-2的甲基化反应结合GC-MS分析表明,组分EPS-1A和EPS-1B糖链主要由→3)-D-Glcp-(1→,→6)-D-Galp-(1→,→4)-D-Glcp-(1→和→6)-D-Manp-(1→组成,末端为Glcp-(1→;组分EPS-2糖链主要由→6)-D-Galp-(1→和→6)-D-Manp-(1→组成,末端为D-Glcp-(1→。组分EPS-1A、EPS-1B和EPS-2的糖苷键构型为α型和β型的混合物。综上,该研究将会为菌株NM18所产胞外多糖的生物活性研究及应用提供理论依据。     

Monitoring cell substrate interactions in exopolysaccharide-based films reinforced with chitin whiskers and starch nanoparticles used as cell substrates

Exopolysaccharides (EPS) extracted from Nostoc commune cyanobacteria were used to prepare low-adhesion cell substrates for tumor-selective cell growth. The substrates were reinforced with chitin whiskers and starch nanoparticles and characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and tensile tests. Two anchorage independent cells, green fluorescent protein-modified HeLa and THP-1 cells were seeded on the samples to assess their interaction with the composites. The results confirmed the cell–surface interaction of EPS-based composites. The mechanical properties of these films can be tailored by controlling the type and concentration of the reinforcement, which can be used in the design of different types of biomaterials.     

一株海洋真菌Sw-25产胞外多糖发酵条件研究

通过对海洋真菌Sw-25发酵,研究不同碳源、氮源、培养基初始pH、温度及接种量、装液量对海洋真菌Sw-25产胞外多糖的影响.结果表明,最适培养基组成为:麦芽糖20 mg/L,酵母膏5 mg/L,海水400 mL/L,蒸馏水600 mL/L,培养基初始pH 6.0～6.5.最适发酵条件为:250 mL三角瓶装量80 mL,接种量为6%,24℃培养96 h.在此条件下,海洋真菌Sw-25产胞外多糖1.28 g/L.     

海参肠道中高产胞外多糖酵母的筛选及发酵条件

从大连海域的海参肠道中筛选得到一株产胞外多糖较高的酵母菌HS-J9,经形态学和26SrDNA序列分析,初步鉴定为季也蒙假丝酵母(Meyerozyma guilliermondii),GenBank检索号为KF668241。采用苯酚-硫酸法和响应面法对该高产菌株进行胞外多糖测定及发酵条件优化。通过单因素试验确定了pH、接菌量和发酵时间3个主要因素对发酵产糖量的影响,根据Box-Behnken中心组合设计原理确定显著性因子的最佳水平,并以胞外多糖产量为响应值进行回归分析。结果表明,当pH为6.6、接菌量4%、发酵时间41.3h时,HS-J9的胞外产糖量最大,为0.762 mg/mL,比优化前的产胞外多糖量(0.616mg/mL)提高了23.67%。