Differential induction, purification and characterization of cold active lipase from Yarrowia lipolytica NCIM 3639

The production, purification and characterization of cold active lipases by Yarrowia lipolytica NCIM 3639 is described. The study presents a new finding of production of cell bound and extracellular lipase activities depending upon the substrate used for growth. The strain produced cell bound and extracellular lipase activity when grown on olive oil and Tween 80, respectively. The organism grew profusely at 20 °C and at initial pH of 5.5, producing maximum extracellular lipase. The purified lipase has a molecular mass of 400 kDa having 20 subunits forming a multimeric native protein. Further the enzyme displayed an optimum pH of 5.0 and optimum temperature of 25 °C. Peptide mass finger printing reveled that some peptides showed homologues sequence (42%) to Yarrowia lipolytica LIP8p. The studies on hydrolysis of racemic lavandulyl acetate revealed that extracellular and cell bound lipases show preference over the opposite antipodes of irregular monoterpene, lavandulyl acetate.     

醋酸钙复盐对微生物生长的影响

应用四醋酸钙对黑曲霉、黄曲霉、米曲霉、链格孢霉等霉菌和大肠杆菌、枯草杆菌、绿脓杆菌、金黄色葡萄球菌等细菌生长影响作了研究,并将四醋酸钙与醋酸钙、苯甲酸钠对上述微生物的生长抑制作用加以比较。0.4％四醋酸钙对上述细菌的生长有明显的抑制作用。对上述霉菌生长亦有一定的抑制作用。当其与苯甲酸钠协同使用时,能更明显地抑制微生物生长。实验结果表明四醋酸钙很可能是一种安全性高、成本低的新型食品防腐剂。     

Cyclic biphalin analogues with a novel linker lead to potent agonist activities at mu,delta, and kappa opioid receptors

In an effort to improve biphalin’s potency and efficacy at the µ-(MOR) and δ-opioid receptors (DOR), a series of cyclic biphalin analogues 1–5 with a cystamine or piperazine linker at the C-terminus were designed and synthesized by solution phase synthesis using Boc-chemistry. Interestingly, all of the analogues showed balanced opioid agonist activities at all opioid receptor subtypes due to enhanced κ-opioid receptor (KOR) activity. Our results indicate that C-terminal flexible linkers play an important role in KOR activity compared to that of the other cyclic biphalin analogues with a hydrazine linker. Among them, analogue 5 is a potent (Ki?=?0.27, 0.46, and 0.87?nM; EC₅₀?=?3.47, 1.45, and 13.5?nM at MOR, DOR, and KOR, respectively) opioid agonist with high efficacy. Based on the high potency and efficacy at the three opioid receptor subtypes, the ligand is expected to have a potential synergistic effect on relieving pain and further studies including in vivo tests are worthwhile.     

沼泽红假单胞菌乙酸光合放氢研究

依据光合细菌生长代谢特性和有机废水降解主要产物类型,11种有机物被用于沼泽红假单胞菌（Rhodopseudomonas palustris）Z菌株的光合产氢研究,其中,乙酸反应体系产氢活性最高。在此基础上,研究了该菌株的生长与产氢动力学行为,探求了影响该菌株光合放氢的主要限制性影响因素。结果表明,该菌株产氢与生长部分相关。种子培养基和菌龄对产氢活性有明显影响。细胞最适产氢和生长所需要的光照强度和温度基本一致。当种子来源于硫酸铵高菌龄预培养物或谷氨酸钠对数期预培养物时,该菌株产氢活性显著增加,产氢延滞期明显缩短。氧浓度和接种量对产氢活性也有显著影响。供氢体和氮源浓度直接决定细胞的生长与光放氢活性。在低于70 mmol/L乙酸钠和15 mmol/L谷氨酸钠时,产氢活性随底物浓度的增加而增强。谷氨酸钠浓度高于15mmol/L时,由于游离NH₄⁺的出现,产氢活性受到抑制,但却明显刺激细胞的生长。在标准状况下,该菌株的最大产氢速率可达19.4 mL·L^-1·h^-1。     

花生种子高纯度DNA的提取（简报）

花生种子高纯度ＤＮＡ的提取（简报）王艳,何军贤,傅家瑞（中山大学生命科学学院,广州５０２７５）关键词花生;种子;ＤＮＡ;十六烷基三甲基溴化铵ＲＡＰＩＤＡＮＤＥＦＦＩＣＩＥＮＴＰＵＲＩＦＩＣＡＴＩＯＮＯＦＤＮＡＦＲＯＭＰＥＡＮＵＴ（ＡＲＡＣＨＩＳＨＹＰ...     

不同生育时期增铵营养对小麦生长及氮素利用的影响

通过两年的田间试验,研究了不同生育时期增铵营养(EAN)对小麦生长和氮素利用的影响.结果表明,田间增铵营养促进了小麦植株的生长和氮素吸收.其中基肥、分蘖期、拔节期EAN提高了小麦的干物质积累量、地上部氮积累量、有效穗数、叶面积指数、叶片叶绿素含量以及小麦的籽粒产量;孕穗期EAN效果不明显;全生育期EAN在促进生长方面的效果并无明显优势,但可有效降低土壤N₃^--N的淋溶损失.与对照相比,EAN提高了氮流效率和吸收效率,但以拔节前处理最为明显.拔节期EAN主要在于改善后期的叶片光合性能,并促进同化物向籽粒的再分配,而基肥和分蘖期EAN主要在于提高有效分蘖数.     

New pathways for ammonia conversion in soil and aquatic systems

Ammonia conversion processes are essential for most soil and aquatic systems. Under natural conditions, the many possible reactions are difficult to analyze. For example, nitrification and denitrification have long been regarded as separate phenomena performed by different groups of bacteria in segregated areas of soils, sediments or aquatic systems sequentially in time. It has now been established that strict segregation in place and time of the two processes is not necessary and that both denitrifiers and nitrifiers have versatile metabolisms. However, the rates described for aerobic denitrifiers are very low compared to the rates observed under anoxic conditions. Also the rates of nitrifier denitrification are quite low, indicating that these conversions may not play an important role under natural conditions. In addition, these processes often result in the emission of quite large amounts of undesirable products, NO and N₂O. Heterotrophic nitrification might be of relevance for systems, that contain a high carbon to nitrogen ratio. Recently, a novel process (Anammox) has been discovered in which ammonium serves as the electron donor for denitrification of nitrite into dinitrogen gas. ¹⁵N labeling studies showed that hydrazine and hydroxylamine were important intermediates in this process. Enrichment cultures on ammonium, nitrite and bicarbonate resulted in the dominance of one morphotypical microorganism. The growth rate of the cultures is extremely low (doubling time 11 days), but the affinity for ammonium and nitrite and the conversion rates (9.2 10^–4 mol kg^–1 s^–1) are quite high. Some of the reported high nitrogen losses in soil and aquatic systems might be attributed to anaerobic ammonium oxidation. In addition, this conversion offers new opportunities for nitrogen removal, when it is combined with recently developed processes for partial nitrification.     

厌氧氨氧化膨胀床反应器的运行性能

试验研究了以竹炭为载体的厌氧氨氧化膨胀床反应器的运行性能.接种反硝化污泥,用模拟废水可成功启动该反应器:运行至144 d时,容积总氮去除率达到3.02 kg N/m3/d.这是国内文献报道的最高水平.动力学分析表明.这种反应器的最大容积总氮去除率可迭12.77 kg N/m3/d.具有很大的脱氮潜能.反应器的启动过程可分为菌体自溶、活性延滞和活性提高三个阶段.与此相应,污泥性状也从黄褐色絮状污泥变为棕灰色颗粒污泥和红色颗粒污泥.红色颗粒污泥以杆茵和球菌为主.厌氧氨氧化活性可达0.56mg TN/(mgprotein)/h,它们是反应器厌氧氨氧化功能的主要承载者.     

不同硝化抑制剂对红壤氮素硝化作用及玉米产量和氮素利用率的影响

本研究分析添加不同种硝化抑制剂及其组合的高效稳定性氯化铵氮肥对红壤硝化作用、玉米产量和氮肥利用率的影响,旨在筛选出适合酸性红壤的高效稳定性氯化铵态氮肥。在氯化铵中分别添加硝化抑制剂2-氯-6-三甲基吡啶(CP)、3,4-二甲基吡唑磷酸盐(DMPP)和双氰胺(DCD)及其组合,制成6种高效稳定性氯化铵态氮肥,以不施氮肥(CK)和施氯化铵(N)为对照,进行等氮量玉米盆栽试验。结果表明: 与N处理相比,CP+DMPP和DMPP+DCD处理红壤中铵态氮含量提高56%～62%,显著高于CP、DMPP和DCD处理;土壤表观硝化率显著降低33%～34%。添加硝化抑制剂及其组合的6个处理均显著提高了玉米生物量和氮肥吸收利用率。与N处理相比,单独添加硝化抑制剂处理生物量均显著高于硝化抑制剂组合处理,平均提高1.3倍;添加DCD处理效果最显著,玉米籽粒产量、吸氮量和氮肥吸收利用率分别显著提高4.1、6.3和4.4倍。为了达到既能低成本又能提高产量和氮肥利用率的效果,在红壤上添加硝化抑制剂DCD是最佳选择。