Surfactin生物表面活性剂及其驱油研究进展

表面活性素（surfactin）是一类由革兰氏阳性的枯草芽孢杆菌产生的脂肽（lipopeptide）型生物表面活性剂，因其具有优于化学合成表面活性剂的若干优点，如低毒性、高生物降解性、更好的环境相容性，且在极端环境下稳定性好，在提高石油采收率方面有较好的应用潜力，但是目前只有少数的生物表面活性剂可以大规模生产实现工业化应用。本文介绍了surfactin生物表面活性剂的化学结构和生物合成机制，并对其发酵生产过程的影响因素进行分析，为提高其生产经济性探索不同的策略，例如使用更便宜的原材料、优化培养基组分、优化反应器等，系统论述了surfactin生物表面活性剂的驱油机理和其与化学合成表面活性剂的复配研究，同时针对其应用时的不足之处提出研究新思路。     

Double-Headed Cationic Lipopeptides: An Emerging Class of Antimicrobials

Antimicrobial peptides (AMPs) constitute a promising tool in the development of novel therapeutic agents useful in a wide range of bacterial and fungal infections. Among the modifications improving pharmacokinetic and pharmacodynamic characteristics of natural AMPs, an important role is played by lipidation. This study focuses on the newly designed and synthesized lipopeptides containing multiple Lys residues or their shorter homologues with palmitic acid (C₁₆) attached to the side chain of a residue located in the center of the peptide sequence. The approach resulted in the development of lipopeptides representing a model of surfactants with two polar headgroups. The aim of this study is to explain how variations in the length of the peptide chain or the hydrocarbon side chain of an amino acid residue modified with C₁₆, affect biological functions of lipopeptides, their self-assembling propensity, and their mode of action.     

鲫鱼贮藏过程中微生物菌相PCR-DGGE分析及其防腐保鲜

采用聚合酶链式反应-变性梯度凝胶电泳(polymerase chain reaction-amplification and denaturing gradient gel electrophorsis,PCR-DGGE)技术,分析4℃冷藏条件下鲫鱼肌肉和鱼鳃的菌相组成及变化,并利用不同浓度(效价分别为67 608、32 359、2 239、1 820、1 157 IU/m L)抗菌脂肽溶液对鲫鱼进行浸泡处理,以未处理作为对照,分别测定其菌落总数、挥发性盐基氮(total volatile basic nitrogen,TVB-N)、p H值和硫代巴比妥酸(thiobarbituric acid,TBA)等指标,评价抗菌脂肽对鲫鱼冷藏保鲜效果。结果表明:鲫鱼贮藏过程中的微生物具有多样性,PCRDGGE技术确定气单胞菌属(Aeromonas sp.)、假单胞菌属(Pseudomonas sp.)、不动杆菌属(Acinetobacter sp.)和热杀索丝菌属(Brochothrix thermosphacta)为鲫鱼鱼肉的主要腐败菌群,荧光假单胞菌是鲫鱼贮藏过程中的优势腐败菌。而棉子糖乳球菌属(Lactococcus raffinolactis)、从毛单胞菌属(Comamonas sp.)和气单胞菌属(Aeromonas sp.)为鲫鱼鱼鳃的主要腐败菌群,表明鱼肉和鱼鳃在贮藏过程中,导致腐败的主要腐败菌群有一定差异性。同时,不同浓度的抗菌脂肽对鲫鱼均有明显的防腐保鲜作用,有效抑制了鲫鱼菌落总数、TVB-N值和TBA值的增加以及p H值的升高。其中,高浓度抗菌脂肽(效价为67 608 IU/m L)在4℃贮藏条件下使鲫鱼的货架期延长了6 d,说明抗菌脂肽对鲫鱼具有良好的保鲜作用,能明显延缓鲫鱼的腐败变质。     

1株产脂肽类抗生素芽孢杆菌的鉴定及脂肽类抗生素相关基因克隆

从小麦根际土壤中分离得到一株对禾谷镰刀菌有拮抗作用的菌株7F1。以菌株7F1基因组总DNA为模板,通过16S rDNA和gyrB基因序列分析,鉴定7F1为多粘类芽孢杆菌。本实验对该菌种产拮抗物的稳定性进行了研究,同时,应用特异性引物对7F1中脂肽类抗生素合成相关基因进行检测。结果表明:该菌产生的拮抗物在40~90℃保持较高的活性;在蛋白酶K、胃蛋白酶和胰蛋白酶处理后,抑菌活性显著下降;在pH 3.0~10.0具有抑菌活性;使用已报道的脂肽类抗生素基因片段设计的引物进行聚合酶链式反应扩增,从该菌的基因组DNA中扩增得到了3种bamC、eriSa、ituC脂肽类抗生素合成酶基因。此研究结果对脂肽类抗生素进一步的分离提供了重要参考。     

Time‐dependent dosing of Fe2+ for improved lipopeptide production by marine Bacillus megaterium

BACKGROUND: Lipopeptide production is strongly influenced by trace metals. The availability of free Fe²⁺ in the media throughout the process of fermentation was found to be very critical. Since free Fe²⁺ was reported to be sequestered by the lipopeptide as it was produced, intermittent feeding of Fe²⁺ was strategized and optimized for enhanced lipopeptide production by marine Bacillus megaterium in glucose mineral salts medium (GMSM). RESULTS: Studies with the single‐dose Fe²⁺ (0.48 mmol L^?1) supplementation after 8 h of fermentation resulted in lipopeptide concentration of 3.3 ± 0.1 g L^?1. Lipopeptide production was further enhanced to 4.2 ± 0.15 g L^?1 by adopting a multi‐dose Fe²⁺ feeding strategy. The maximum product yield (Y_P/S) of 0.24 ± 0.02 g g^?1 with specific product formation rate (q_p) of 0.124 ± 0.01 g g^?1 h^?1 was achieved when 0.48 mmol L^?1 Fe²⁺ was fed intermittently at different times as per the designed strategy. CONCLUSION: Lipopeptide concentration was improved 4.7‐fold by single‐dosing and 5.8‐fold by multiple dosing of Fe²⁺, when compared with GMSM without Fe²⁺ supplementation. Copyright © 2012 Society of Chemical Industry     

环脂肽生产菌株Bacillus subtilisOw-097生物合成条件优化研究

为进一步提高环脂肽的产量，应用单因素试验与正交设计对Bacillu ssubtilis0w-097产环脂肽深层液体发酵培养基组成及发酵条件进行了优化。优化的发酵培养基组成为：玉米粉4．0％、豆粕粉3．0％、CaCl21．2g／L、KH2PO42．0g／L、Na2HPO48．0g／L和起始pH值为8．5。最佳培养备件：装瓶量为125mL，菌龄为24h，接种量为4％，培养温度为37℃，摇床转速为200rpm。在此优化条件下环脂肽的产量为1．026g／L。     

凝结芽孢杆菌XZQ-16抗菌脂肽分离鉴定及抗菌特性

对凝结芽孢杆菌（Bacillus coagulans） XZQ-16脂肽分离鉴定并探讨其抗腐败菌特性。通过酸沉、硅胶柱层析和Sephadex LH-20层析对脂肽分离纯化,利用傅里叶红外光谱（FT-IR）和反相高效液相色谱（RP-HPLC）对脂肽分析鉴定。结果表明,硅胶柱层析得到三个流分具有明显抗菌活性;Sephadex LH-20层析分离出四个洗脱峰,洗脱峰Ⅲ抑菌活性明显;FT-IR确定纯化的抗菌物质中含有脂肽类化合物;RP-HPLC分析并与标准样对照确定分离的抗菌物质为伊枯菌素（iturin）和表面活性素（surfactin）同系物。脂肽宽泛的pH范围（4.0~12.0）酸碱耐受性好,在120℃以下保温30 min抗菌活性在80%以上。脂肽能抑制多种常见的食源性致病菌,包括革兰氏阳性菌如蜡样芽孢杆菌、金黄色葡萄球菌、单核增生李斯特菌、藤黄微球菌等以及革兰氏阴性菌如大肠杆菌、铜绿假单胞菌、沙门氏菌、痢疾志贺氏菌等。同商业化应用的乳酸链球菌素（nisin）和多粘菌素相比,菌株XZQ-16脂肽除了对细菌具有明显抑制作用,还对真菌如白色念珠菌、毕赤酵母和黑曲霉也有抑制作用。B.coagulans XZQ-16脂肽表现出极高的稳定性和广谱抗菌活性,为在食品、畜牧、医药、化妆品及植物保护等领域的应用奠定理论基础。     

脂肽类生物表面活性剂Surfactin的乳化性

采用白金板法对Surfactin的表面活性进行研究,并用浊度法和离心法对其乳化性进行研究。结果表明:Surfactin的临界胶束浓度为9.03×10-5 mol/L,可将水的表面张力由73.98 m N/m降至最低27.48 m N/m。在浓度为1×10-3~1.2×10-2 mol/L的NaCl溶液中,Surfactin溶液的表面张力随盐浓度升高逐渐降低并最终稳定在34 m N/m;Surfactin在121℃处理20 min后,其表面张力仍能保持在37.10 m N/m;在pH值为2~12范围内,其表面活性稳定并良好;表明Surfactin具有较强的NaCl浓度、温度、pH值的耐受性。浊度法测得Surfactin亲水亲油平衡(hydrophile lipophilic balance,HLB)值为14,对所需HLB值为12~16的油相乳化性能良好。     

Biosurfactants for cosmetic applications

Biosurfactants are biologically-produced, natural surface active agents and are synthesized by a range of microorganisms. These compounds include glycolipids, lipopeptides and phospholipids. The yields of biosurfactants in microbial fermentations may be as high as 150g l⁻¹ and may be increased by optimizing production conditions and by strain improvement. Biosurfactants display very low critical micelle concentration (CMC) values when compared with conventional surfactants and are stable at a wide range of temperatures, pH values and salinities. They show many promising characteristics for cosmetic applications.     

中间苍白杆菌对含蜡原油除蜡降粘分析

蜡质不仅使含蜡原油黏度升高，而且会析出积聚在管壁上降低管输效率。从原油污染淤泥中分离出一株产表面活性剂的烃降解菌F-1，经16S rDNA鉴定为中间苍白杆菌。与原油作用7 d 后，能将蜡含蜡量为15.2%的高含蜡原油处理为蜡含蜡量为9.1%的含蜡原油，原油蜡质量分数降低40.1%，原油黏度降低21%以上，细胞疏水性达28.1%。通过傅里叶红外光谱鉴定该菌产生的生物表面活性剂为脂肽类。添加该菌上清液到液体石蜡 可形成91.49 mm的排油圈，能够显著降低培养基表面张力，对液体石蜡乳化系数达到65%。