溶氧(DO)对混菌发酵生产Nisin影响的研究

Nisin(乳酸链球菌素)是由乳酸菌产生的一种抑菌活性肽。其在生产过程中需要控制发酵体系的pH,以避免由于乳酸菌代谢积累的乳酸导致pH迅速降低抑制菌体生长。本文采用以能够代谢消耗乳酸的酵母菌为辅助发酵菌的新型混菌发酵方法,在小试条件下研究了在混菌发酵过程中对菌体特别是酵母菌代谢有显著影响的因素溶氧(DO)对混菌发酵生产过程中发酵体系的pH与乳酸含量的变化nisin产量的影响。结果表明,不同水平溶氧对混菌发酵体系中两种菌的生长及代谢产物生成有一定影响。DO 10%与DO 30%时的nisin效价的水平波动范围为24.35%;在分阶段控制发酵体系溶氧水平的条件下获得了较高的nisin效价,效价水平比恒定溶氧提高45.38%。说明分阶段控制发酵体系溶氧水平是较为理想的溶氧控制策略。     

BTI和Nisin复合涂膜液对鲈鱼鱼糜的保鲜效果

以明胶和壳聚糖为基本成分制备乳酸链球菌素（nisin）和荞麦胰蛋白酶抑制剂（buckwheat trypsin inhibitor,BTI）的复合涂膜保鲜剂。用此复合保鲜剂对鲈鱼鱼糜进行涂膜处理,以菌落总数、挥发性盐基氮（total volatile basic nitrogen,TVB-N）含量、硫代巴比妥酸反应物（thiobarbituric acid reactive substances,TBARS）含量、pH 值、蒸煮损失率等为检测指标,研究复合液对鲈鱼鱼糜的保鲜效果。结果表明,nisin和BTI联合使用可有效抑制鲈鱼鱼糜4℃贮藏过程中微生物的生长,并显著减缓TVB-N及TBARS的增长速率,降低鱼糜的蒸煮损失率。BTI可以提高nisin对蛋白酶的抗性,增强nisin的稳定性,有利于鱼糜的抗菌保鲜,延长鲈鱼鱼糜的冷藏货架期。     

Nisin与天然植物提取物复配的抑菌性能研究

为了研究nisin与天然植物提取物复配的抑菌性能,用效价表征复配物的抑菌效力、比浊法测其广谱性.结果表明:nisin与黄连、大黄、黄芩提取物复配的配比分别为1:6、1:5、1:6时,复配物效价分别是nisin的1.78、1.54、1.27倍.nisin与黄连,大黄,黄芩复配后能抑制枯草芽孢杆菌、大肠杆菌、酿酒酵母菌.黄连提取物与nisin复配后抑菌效果最好,大黄次之,黄芩最差.     

补料分批发酵泡沫分离耦合对乳链菌肽生产的影响

为了解除发酵过程中目标产物乳链菌肽(nisin)的抑制,研究了发酵泡沫分离耦合。通过正交试验确定了合适的耦合操作条件:气速40 mL/min、pH 5.75、通气时间90 min。在此条件下进行实验,nisin失活最小(6.1%)。随后,在耦合操作的基础上进行了补料实验。结果表明,在发酵末期时nisin总效价(4 813 IU/mL)和总产量(3.37×106IU)相对于对照组的总效价(4 097 IU/mL)和总产量(2.46×106IU)分别提高了17.5%和37.0%。     

MJL交联酶聚体的制备及性质研究

本实验制备MJL交联酶聚体并对其性质进行研究。运用交联酶聚体技术制备MJL交联酶聚体;测定游离MJL和CLEAs的酶活,最适pH和温度;比较MJL交联酶和游离酶在室温下的稳定性。方法:利用戊二醛做交联剂制备MJL交联酶聚体;α-乙酸萘酯法测定游离MJL及MJL交联酶聚体的最适pH和温度。实验结果显示,交联后酶适应温度范围变宽,最适pH较游离酶(pH7.0)向酸性偏移。结论:交联后脂肪酶聚活性变化较低,对温度、pH的耐受性提高,稳定性也有所提高。     

酸解氧化小麦淀粉的制备及性能

以小麦淀粉为原料,盐酸为酸解剂,次氯酸钠为氧化剂,对酸解小麦淀粉的制备及性能进行了研究.考察了反应时间、反应温度、pH、次氯酸钠用量、酸解氧化顺序对酸解氧化小麦淀粉羧基含量的影响,采用糊滴定法测定羧基含量.比较了小麦淀粉、酸解小麦淀粉、氧化小麦淀粉及酸解氧化小麦淀粉性能.结果表明,制备酸解氧化小麦淀粉的较佳工艺条件为:反应温度40℃,反应时间2h,pH9.0,先酸解后氧化顺序优于先氧化后酸解顺序.小麦淀粉经酸解氧化后,其抗酸性、抗碱性、冻融稳定性均得到改善,蓝值增加,膨胀能力降低.小麦淀粉经酸解、氧化后,热稳定性变差;酸解提高了小麦淀粉的熔融焓,而氧化使其熔融焓降低.     

大豆分离蛋白的超滤制备及其功能特性的研究

研究了超滤法制备大豆分离蛋白 (SPI)过程中温度、压力、pH值对膜通量的影响 ,并确定其最佳工艺参数。同时研究超滤法制备的大豆分离蛋白的功能特性 ,结果表明 ,与碱溶酸沉法制备的大豆分离蛋白相比 ,超滤法制备的大豆分离蛋白的NSI、PDI、乳化性、发泡性均有提高 ,但其凝胶性、黏度比前者要差。在一定 pH值范围内 ,碱溶酸沉法制备的SPI的泡沫稳定性优于超滤法制备的SPI     

β-环糊精对维生素M的增溶及稳定作用

制备了维生素M-β-环糊精包合物,考察了不同温度和pH对β-环糊精增溶维生素M的影响,确定了包合物的最佳工艺;对包合物、物理混合物和加有维生素C的包合物在光照、避光、不同温度以及添加不同浓度的防腐剂条件下进行稳定性研究,紫外分光光度法测定维生素M的含量。结果表明:包合物的最佳工艺为pH8,温度25℃;制备的β-环糊精包合物中维生素M的量最大可达60.764μg/mL;避光、低温、pH8条件下包合物中维生素M的稳定性最好,且添加适量的抗氧化剂可以增强其稳定性。      

大豆分离蛋白的超滤制备及其功能特性的研究

研究了超滤法制备大豆分离蛋白(SPI)过程中温度、压力、pH值对膜通量的影响，并确定其最佳工艺参数。同时研究超滤法制备的大豆分离蛋白的功能特性，结果表明，与碱溶酸沉法制备的大豆分离蛋白相比，超滤法制备的大豆分离蛋白的NSI、PDI、乳化性、发泡性均有提高，但其凝胶性、黏度比前者要差。在一定pH值范围内，碱溶酸沉法制备的SPI的泡沫稳定性优于超滤法制备的SPI。     

β-环糊精对维生素M的增溶及稳定作用

制备了维生素M-β-环糊精包合物,考察了不同温度和pH对β-环糊精增溶维生素M的影响,确定了包合物的最佳工艺;对包合物、物理混合物和加有维生素C的包合物在光照、避光、不同温度以及添加不同浓度的防腐剂条件下进行稳定性研究,紫外分光光度法测定维生素M的含量。结果表明:包合物的最佳工艺为pH8,温度25℃;制备的β-环糊精包合物中维生素M的量最大可达60.764μg/mL;避光、低温、pH8条件下包合物中维生素M的稳定性最好,且添加适量的抗氧化剂可以增强其稳定性。     

Liposome encapsulated nisin Z: optimization,stability and release during milk fermentation

Liposomes prepared from different proliposomes (Pro-lipo^® H, Pro-lipo^® S, Pro-lipo^® C and Pro-lipo^® DUO) were tested for their capacity to encapsulate nisin Z. Factors affecting the entrapment process (pH and concentration of nisin Z solution and cholesterol concentration in the lipid membranes) were optimized. The use of nisin Z monoclonal antibodies made it possible to quantify, using a competitive enzyme immunoassay, and visualize, using transmission electron microscopy, nisin Z. Nisin Z was entrapped in different liposomes with encapsulation efficiencies (EE) ranging from 9.5% to 47%. The pH of nisin Z aqueous solution and nisin Z concentration had a significant effect on the amount of encapsulated nisin. An increase in cholesterol content in lipid membranes up to (20%, w/w) resulted in a slight reduction in EE. Nisin-loaded vesicles did not severely disturb Cheddar cheese fermentation and showed stability to Cheddar cheese temperature cycle. Long term stability of liposome-encapsulated nisin Z was demonstrated for 27 days at 4°C in different media including milk with different fat levels (3.25%, 2.0% and 1.0%), skim milk, sweet whey and phosphate buffer saline (PBS). Liposome stability determined as the quantity of released nisin Z was highest in milk followed by PBS and whey, respectively.     

乳酸链球菌素对乳酸菌抑菌作用的研究

目的：为了观察Nisin 对乳酸菌的抑菌效果,探讨Nisin 作为食品级载体筛选方法的最佳抑菌浓度和持续时间。方法：采用试管稀释法和纸片扩散法检测Nisin 对乳酸菌的抑菌浓度,并根据乳酸菌的OD600nm 作出生长曲线,以研究Nisin 对乳酸菌的抑菌效果。结果：Nisin 对乳品工业常用乳酸菌具有较强的抑菌作用,仅某些乳酸乳球菌对Nisin 表现出抗性;Nisin 对乳酸菌有较持久的抑菌效果,可达30～48h 以上。结论：该实验为Nisin 作为食品级载体筛选方法的最佳抑菌浓度和持续时间提供了依据。     

NISIN: A BACTERIOCIN WITH A POTENTIAL USE IN BREWING

Depending on the amount used and the strain of bacteria involved, nisin either kills lactic acid bacteria or inhibits their growth. In medium inoculated with approximately 10⁵ cells ml^?1 of a sensitive strain of Lactobacillus (BSO 375) nisin, added at levels recommended for commercial use (100 International Units ml^?1, killed all the cells in less than 6 h. In the absence of nisin this inoculum grew to a concentration of 10¹⁰ cells ml^?1 in about 50 h. Lower nisin concentrations killed fewer cells but inhibited the growth of those still viable. For the more resistant strain Lactobacillus (BSO 343) growth was only inhibited at the higher nisin concentrations. Nisin maintained its activity against lactic acid bacteria in brewing fermentations. It had no effect on the growth and fermentative performance of the 9 brewing yeast strains tested, and, in a pilot brewery fermentation, had no deleterious affect on the taste of the beer produced. Nisin could be used either as a preventative measure by regular addition to fermentations, or as a remedial measure once contamination by lactic acid bacteria had been detected.     

Effect of temperature,pH and film thickness on nisin release from antimicrobial whey protein isolate edible films

BACKGROUND: An active packaging film based on whey protein isolate (WPI) was developed by incorporating nisin to promote microbial food safety. The effect of temperature and pH on the release of nisin from edible films of different thickness was investigated. The film mechanical properties and inhibitory effect were also evaluated. RESULTS: Nisin release was significantly favoured by low pH, with the highest release after 24 h (1325 IU), which was not significantly affected by temperature (5 or 10 °C). Thickness significantly affected film elongation, with thicker films showing the highest elongation (54.3 ± 2.7%). Water vapour permeability (0.15 ± 0.4 g mm m^?2 kPa^?1 h^?1) and elastic modulus were not significantly affected by thickness. The highest nisin effective diffusivity (5.88 × 10^?14 m² s^?1) was obtained using a solution at pH 4, 112 µm film thickness and a temperature of 5 °C. More than four log cycles of Brochotrix thermosphacta were reduced from the surface of a ham sample after 8 days of incubation at 4 °C by the active WPI film containing 473 IU cm^?2 nisin. CONCLUSION: Nisin diffusivity from WPI edible films was favoured at lower pH and film thickness. This active packaging film may be used to preserve the quality and safety of meat products. Copyright © 2009 Society of Chemical Industry     

重组牛乳铁蛋白N末端多肽对真空包装猪肉品质的影响

以Nisin和乳酸作为参照,采用本试验室获得的重组牛乳铁蛋白肽对生鲜猪肉进行保藏试验。生鲜猪肉浸沾并真空包装后置于4℃下存放,测定肉样的微生物数、抗氧化值(TBA)、pH值、肉的红度值(Huntera)及感官评价。结果显示,重组的牛乳铁蛋白肽保鲜效果优于Nisin组,接近乳酸组。其保鲜期可达到19d。     

HPLC评价Nisin物化特性及其在食品中提取研究

乳酸链球菌素(Nisin)是一种天然防腐剂,采用高效液相色谱法(HPLC)定性定量评价其溶解度、稳定性、生物利用度及在食品中提取回收率的研究。结果表明:当稀盐酸pH=2,50 ℃时,Nisin溶解度最大为30.22 mg/mL;Nisin在温度超过50 ℃时易失活,(4±0.5) ℃利于减缓降解;Nisin在生物条件下利用度为100%,是一种无毒、无害的多肽。在4种食品中,辣蒜酱中Nisin最为稳定,以15 mL乙腈、10 mL稀盐酸(pH=2)为提取溶剂,超声20 min、50 ℃下水浴40 min为处理条件,得到Nisin保留时间为19.067 min;峰分型尖锐明显且基线平稳;标准曲线线性关系好,回收率为92.54%,RSD<3%。     

滚揉腌制液中添加Nisin对川香鸡柳的保鲜效果

在川香鸡柳滚揉腌制液中添加不同含量的Nisin(0.1、0.2、0.3、0.4g/kg,按鸡小胸质量计),结合托盘包装技术对其进行保鲜研究。通过测定其在(4.0±0.5)℃条件下贮藏期间的菌落总数、水分活度、pH值、色差值、贮藏损失各项指标,分析Nisin对川香鸡柳的保鲜效果。结果表明:滚揉腌制液中添加Nisin能显著抑制川香鸡柳中菌落总数的增长(P<0.05),贮藏第8天时最明显,与对照组相比,处理组菌落总数可降低3.32 lg(CFU/g);Nisin可显著提高川香鸡柳贮藏后期色泽亮度和黄度;显著延缓第8天后pH值的升高(P<0.05);但对水分活度影响不显著。综合各因素,添加0.3g/kg Nisin保鲜效果最佳。在滚揉腌制液中添加Nisin对川香鸡柳具有良好的保鲜效果。     

Antimicrobial activity of nisin against Oenococcus oeni and other wine bacteria

Nisin is a bacteriocin used against food spoilage bacteria. Sulphur dioxide is a potent antioxidant as well as an antimicrobial agent widely used in the wine industry. In this study we describe the effect of these important antibacterial agents on the growth of a collection of 64 lactic acid bacteria (23 Oenococcus, 29 Lactobacillus, 3 Leuconostoc and 9 Pediococcus), 23 acetic acid bacteria and 20 yeast isolates, most of them recovered from wine. Minimal inhibitory concentrations (MIC) and minimal bactericide concentrations of nisin, potassium metabisulphite and ethanol were determined. Nisin MIC(50) values for the tested isolates were as follows: 0.024, 12.5, 200 and > or micro for oenococci, lactobacilli-pediococci-leuconostoc, acetic acid bacteria and yeasts, respectively. Synergistic effects on bacterial growth inhibition were observed, and potassium metabisulphite MIC(50) values decreased from one to three orders of dilution when it was combined with subinhibitory concentrations of nisin in the growth media. This effect was observed in all lactic acid bacteria species of our study. Significant differences in nisin sensitivity were observed between Gram-positive and Gram-negative bacteria, and between Oenococcus oeni and other species of lactic acid bacteria. It is concluded that appropriate combinations of nisin and metabisulphite could control the growth of spoilage bacteria in wine and therefore allow a decrease in the levels of sulphur dioxide currently used by the wine industry.     

乳链菌肽的基因工程研究进展

乳链菌肽是某些Lactococcus lactis和Streptococcus lactis产生的小肽。它对许多革兰氏阳性菌及厌氧菌具有强烈抑制作用,是人们广为应用的一种天然食品防腐剂,但其低产量和高成本而制约着Nisin商业应用。很多研究者尝试通过基因工程方法生产乳链菌肽从而提高其产量。论文综述了Nisin的分子结构、合成及分泌机制、基因工程应用等。