Cloning and Characterization of a Novel Alginate Lyase from Paenibacillus sp. LJ-23

As a low molecular weight alginate, alginate oligosaccharides (AOS) exhibit improved water solubility, better bioavailability, and comprehensive health benefits. In addition, their biocompatibility, biodegradability, non-toxicity, non-immunogenicity, and gelling capability make them an excellent biomaterial with a dual curative effect when applied in a drug delivery system. In this paper, a novel alginate lyase, Algpt, was cloned and characterized from a marine bacterium, Paenibacillus sp. LJ-23. The purified enzyme was composed of 387 amino acid residues, and had a molecular weight of 42.8 kDa. The optimal pH of Algpt was 7.0 and the optimal temperature was 45 °C. The analysis of the conserved domain and the prediction of the three-dimensional structure indicated that Algpt was a novel alginate lyase. The dominant degradation products of Algpt on alginate were AOS dimer to octamer, depending on the incubation time, which demonstrated that Algpt degraded alginate in an endolytic manner. In addition, Algpt was a salt-independent and thermo-tolerant alginate lyase. Its high stability and wide adaptability endow Algpt with great application potential for the efficient preparation of AOS with different sizes and AOS-based products.     

影响香蕉人工种子再生因素研究

以香蕉巴西蕉品种吸芽为诱导材料,获得的诱导小芽作为香蕉人工种子的包埋的胚芽;研究不同浓度的海藻酸钠对香蕉人工种皮包埋材料的影响、不同的CaCI2溶液浸泡时间对种皮的影响及不同基质对人工种子再生的影响。结果表明：选择大小一致及活力旺盛的小芽为胚芽,制备的香蕉人工种子发芽率一致、发芽率高;海藻酸钠浓度为2.0%时,最合适作为香蕉人工种子的包埋材料;MS NAA1.0作为包埋营养液时,香蕉人工种子发芽率及生根率最高,达到99%以上;最适合香蕉人工种子的萌发基质是MS固体培养基。     

超低粘度海藻酸钠制备工艺研究

实验先进行单因素分析,研究海藻酸钠水溶液在不同温度、p H值、反应时间条件下粘度的变化规律,得出单因素条件下制备超低粘度海藻酸钠的最适条件。进而进行正交试验,通过方差分析得出制备超低粘度海藻酸钠的最佳条件为：最适温度65℃,p H值2.5,反应时间是8h。通过喷雾干燥技术将超低粘度的海藻酸钠胶液制备成固体粉末。     

玉米草（Zea Mexicana）与海藻寡糖联合修复石油烃污染土壤的研究

采用玉米草及海藻寡糖联合修复技术研究了石油污染土壤的修复效果,对修复过程中酶活性变化进行了测定,并采用变性梯度凝胶电泳（DGGE）技术测定了土壤中微生物群落的变化。结果表明,种植玉米草可以有效提高土壤中石油烃的降解,与对照相比石油烃降解率增加了11%;加入不同浓度海藻寡糖进一步增加了石油烃的降解效果,降解率最高达到28.6%。种植植物及加入海藻寡糖可以有效提高多酚氧化酶、脱氢酶及尿酶的活性。PCR-DGGE结果表明植物种植及海藻寡糖的加入增加了土壤中微生物数量,其微生物群落结构与未种植植物及修复前土壤相比发生了较大的变化。     

寡聚糖激发子对杨树抗溃疡病的诱导作用

【目的】研究寡聚糖激发子对毛白杨愈伤组织抗杨树溃疡病菌的诱导作用。【方法】分别采用筛选出降解杨树溃疡病菌丝体、壳聚糖、果胶糖且活性较高的寡聚糖激发子A1、B、C3诱导毛白杨愈伤组织,以无菌水处理的毛白杨愈伤组织为对照,并在诱导48 h后挑战接种杨树溃疡病菌,测定毛白杨愈伤组织内Vc、可溶性蛋白质和可溶性糖含量的变化。【结果】经A1、B、C3 3种寡聚糖激发子诱导48 h后接种杨树溃疡病菌,毛白杨愈伤组织中Vc、可溶性蛋白质含量的变化基本上呈单峰曲线,A1、B、C3 3种寡聚糖激发子诱导接种的毛白杨愈伤组织中Vc含量峰值比对照峰值分别提高了99.02％,95.46％和85.64％;寡聚糖激发子诱导接种的毛白杨愈伤组织中可溶性蛋白质含量在发病初期（0～48 h）比对照高,在发病后期（60～96 h）均缓慢下降,而对照毛白杨愈伤组织中的可溶性蛋白含量在60 h时上升到最高峰（4.48 mg/g）,均高于3种寡聚糖激发子诱导接种毛白杨愈伤组织,之后急剧下降,至96 h时为2.33 mg/g,比3种寡聚糖激发子诱导接种毛白杨愈伤组织都低;4个处理毛白杨愈伤组织中可溶性糖含量的变化呈双峰曲线,寡聚糖激发子A1、B、C3诱导接种的毛白杨愈伤组织中可溶性糖含量最大值分别比对照的最大值高42.4%,27.6%和16.5%。方差分析表明,A1、B、C3 3种寡聚糖激发子对挑战接种毛白杨愈伤组织中的Vc、可溶性蛋白质和可溶性糖含量均有极显著影响（P<0.01）。【结论】在一定质量浓度范围内,寡聚糖激发子可诱导毛白杨愈伤组织中的Vc、可溶性蛋白质和可溶性糖含量明显提高,从而增强了其抗杨树溃疡病菌入侵的能力。     

NaCl和CaCl2对海藻酸钠-普通玉米淀粉复合体系理化性质的影响

为探讨NaCl、CaCl2对海藻酸钠-普通玉米淀粉复合体系理化性质的影响,采用快速黏度分析仪、差示扫描量热仪、动态流变仪等,测定添加NaCl和CaCl2对普通玉米淀粉及海藻酸钠-普通玉米淀粉复合体系理化性质的影响.结果表明,NaCl、CaCl2增加普通玉米淀粉、海藻酸钠-普通玉米淀粉复合体系的糊化难度,使样品To、Tp、Tc升高,溶解度、膨胀度降低.NaCl、CaCl2增加普通玉米淀粉、海藻酸钠-普通玉米淀粉复合体系中分子间的相互作用,使样品稠度、G'、G"增加.NaCl、CaCl2使普通玉米淀粉及海藻酸钠-普通玉米淀粉复合体系的糊化焓、老化率降低.海藻酸钠减弱了CaCl2对样品物化性质的影响程度.     

海藻寡糖在农业领域的应用研究进展

海藻寡糖是海藻多糖经过降解得到的一系列寡糖片段,分子量低、水溶性好,具有广泛的生物活性优势,在农业生产中具有广阔的应用前景。文章对近年来海藻寡糖在土壤修复和促进植物生长两方面的研究进展进行综述,同时指出海藻寡糖对土壤重金属的不同作用效果限制了其在土壤修复中的进一步应用、土壤微生物对海藻寡糖—重金属络合物的影响机理不明及海藻寡糖作为植物诱导剂在实际应用中存在局限性等问题。因此,今后在海藻寡糖的利用中应注意以下问题:进行土壤修复时,应针对土壤的酸碱度及重金属污染情况,合理选择海藻寡糖的施用量,确定适宜的修复方式;可将海藻寡糖与其他诱导剂或杀菌剂联合使用以解决其作为诱导剂的局限性;此外,海藻寡糖可作为新型肥料添加剂进行深入开发,以促进其在农业领域的进一步应用。     

The Ameliorative Effect of COST on Diet-Induced Lipid Metabolism Disorders by Regulating Intestinal Microbiota

Background: Chitosan oligosaccharides, with an average molecular weight ≤ 1000 Da (COST), is a natural marine product that has the potential to improve intestinal microflora and resist lipid metabolism disorders. Methods: First, by establishing a mice model of lipid metabolism disorder induced by a high fat and high sugar diet, it is proven that COST can reduce lipid metabolism disorder, which may play a role in regulating intestinal microorganisms. Then, the key role of COST in the treatment of intestinal microorganisms is further confirmed through the method of COST-treated feces and fecal bacteria transplantation. Conclusions: intestinal microbiota plays a key role in COST inhibition of lipid metabolism disorder induced by a high fat and high sugar diet. In particular, COST may play a central regulatory role in microbiota, including Bacteroides, Akkermansia, and Desulfovibrio. Taken together, our work suggests that COST may improve the composition of gut microbes, increase the abundance of beneficial bacteria, improve lipid metabolism disorders, and inhibit the development of metabolic disorders.     

Genome Analysis of a Novel Polysaccharide-Degrading Bacterium Paenibacillus algicola and Determination of Alginate Lyases

Carbohydrate-active enzymes (CAZymes) are an important characteristic of bacteria in marine systems. We herein describe the CAZymes of Paenibacillus algicola {"type":"entrez-nucleotide","attrs":{"text":"HB172198","term_id":"239334117"}}HB172198^T, a novel type species isolated from brown algae in Qishui Bay, Hainan, China. The genome of strain {"type":"entrez-nucleotide","attrs":{"text":"HB172198","term_id":"239334117"}}HB172198^T is a 4,475,055 bp circular chromosome with an average GC content of 51.2%. Analysis of the nucleotide sequences of the predicted genes shows that strain {"type":"entrez-nucleotide","attrs":{"text":"HB172198","term_id":"239334117"}}HB172198^T encodes 191 CAZymes. Abundant putative enzymes involved in the degradation of polysaccharides were identified, such as alginate lyase, agarase, carrageenase, xanthanase, xylanase, amylases, cellulase, chitinase, fucosidase and glucanase. Four of the putative polysaccharide lyases from families 7, 15 and 38 were involved in alginate degradation. The alginate lyases of strain {"type":"entrez-nucleotide","attrs":{"text":"HB172198","term_id":"239334117"}}HB172198^T exhibited the maximum activity 152 U/mL at 50 °C and pH 8.0, and were relatively stable at pH 7.0 and temperatures lower than 40 °C. The average degree of polymerization (DP) of the sodium alginate oligosaccharide (AOS) degraded by the partially purified alginate lyases remained around 14.2, and the thin layer chromatography (TCL) analysis indicated that it contained DP2-DP8 oligosaccharides. The complete genome sequence of P. algicola {"type":"entrez-nucleotide","attrs":{"text":"HB172198","term_id":"239334117"}}HB172198^T will enrich our knowledge of the mechanism of polysaccharide lyase production and provide insights into its potential applications in the degradation of polysaccharides such as alginate.