足球菌ISK—1的发酵产物足球菌素ISK—1的生产最适化

研究了足球菌ＩＳＫ－１发酵中温度，ｐＨ值以及无机阳离子对足球菌素ＩＳＫ－１活性的影响，３７℃，ｐＨ值为５．５～６．０是产生足球菌素ＩＳＫ－１的较适宜条件，Ｍｎ＾２＋和Ｍｇ＾２＋对足球菌素ＩＳＫ－１的产生是必需要，而Ｎａ＾＋，Ｃａ＾２＋，ＮＨ４等阳离子均能提高足球菌素ＩＳＫ－１的活性，其中以Ｎａ＾＋的效果最显著。     

淀粉酶对竹黄菌固态发酵产竹红菌素的影响

研究了竹黄菌在固态发酵产竹红菌素的过程中,搅拌(初始搅拌和搅拌间隔时间)和外加淀粉酶对竹红菌素产量的影响。研究表明,优化后的最佳方案为:初始搅拌在发酵第3天进行,此后的搅拌间隔时间为36 h,外加淀粉酶以细菌中温α淀粉酶和糖化酶的复合添加为最佳,其中细菌中温α淀粉酶在固态发酵初始阶段加入,添加量为2.85 U/g,糖化酶在发酵第3天加入,添加量为29.78 U/g。经过搅拌和外加淀粉酶的研究后,竹红菌素的产量到达了60.74 mg/g,是先前竹红菌素产量报道的3.66倍,并且固态发酵的周期由15 d缩减到了13 d。本研究首次报道了淀粉酶添加应用于固态发酵的研究,并且对竹红菌素产量的提高起到了显著的作用。     

辣椒素对辣椒发酵中乳酸菌的影响

针对辣椒乳酸发酵中的技术问题,采用植物乳杆菌、短乳杆菌、罗伊氏乳杆菌、瑞士乳杆菌、鼠李糖乳杆菌这5种乳酸菌为研究对象,探讨辣椒中主要成分辣椒素和发酵过程中食盐质量浓度对乳酸菌纯培养物生长的影响,同时结合电镜实验讨论辣椒素对乳酸菌的作用效果。结果表明：辣椒素对乳酸菌的生长均有一定的延迟作用,辣椒素对乳酸菌抑制的最低质量浓度为0.133mg/mL,使其对数生长期延后2h,并且随着其质量浓度的增大,这种延迟效果更加明显。同时还降低了培养液中达到稳定期的OD600nm值,降低了0.2左右。通过电镜实验发现,一定质量浓度的辣椒素对乳酸菌细胞具有一定的伤害作用,会破坏其细胞形态及结构,但不会严重影响发酵效果。     

乳酸菌发酵对鳙鱼肉糜菌相与品质的影响

以不同乳酸菌菌株发酵鳙鱼肉糜,对其发酵过程中菌相和品质变化进行分析。结果表明：乳酸菌发酵可显著降低鳙鱼肉糜的pH值,抑制腐败菌的生长,降低挥发性盐基氮的生成量,同时还可增强鳙鱼肉糜的凝胶强度和白度。SDS-PAGE分析表明,乳酸菌发酵可促进鳙鱼肉糜蛋白质的降解。     

磷酸缓冲盐对酸奶增菌发酵过程的影响

在酸奶发酵中,添加0.5%的K2HPO4能使酸奶发酵中产生的酸得到有效缓冲,凝固时间延长1.5～2h的同时,也使酸奶发酵菌的对数生长期延长,每毫升酸奶菌体量提高8～10倍,且有利于嗜热链球菌的生长.与普通的酸奶发酵相比,获得了显著的增菌效果.     

磷酸缓冲盐对酸奶增菌发酵过程的影响

在酸奶发酵中,添加0.5%的K2HPO4能使酸奶发酵中产生的酸得到有效缓冲,凝固时间延长1.5~2h的同时,也使酸奶发酵菌的对数生长期延长,每毫升酸奶菌体量提高8~10倍,且有利于嗜热链球菌的生长。与普通的酸奶发酵相比,获得了显著的增菌效果。      

食盐质量浓度对传统自然发酵圆白菜的菌系结构和代谢的影响

以2、5、8 g/100 mL食盐添加量的传统自然发酵泡菜为研究对象,比较了3 种不同食盐质量浓度的传统自然发酵泡菜中优势菌系结构、卤水pH值和总酸、底物和代谢产物、亚硝酸盐含量的变化。结果表明：乳酸菌主导整个泡菜发酵过程,蔗糖一直被代谢利用,葡萄糖和果糖含量逐步增加,发酵结束时乳酸大量积累。食盐质量浓度对泡菜发酵前期有显著影响,2 g/100 mL食盐质量浓度的泡菜中乳酸菌的繁殖代谢最快,发酵结束时pH值最低,总酸含量最高;5 g/100 mL食盐质量浓度能较好地抑制有害微生物的繁殖,最快通过亚硝峰,产生的乙醇量最高;8 g/100 mL食盐质量浓度抑制了泡菜中乳酸菌的繁殖代谢,使泡菜的成熟期延迟,对蔗糖的利用率最低。     

发酵桦褐孔菌对链脲佐菌素诱导的Ⅱ型糖尿病大鼠降血糖作用的影响

通过高脂饮食联合腹腔注射链脲佐菌素(streptozotocin,STZ)的方法建立Ⅱ型糖尿病(type 2diabetes mellitus,T2DM)大鼠模型,探讨发酵桦褐孔菌(fermented Inonotus obliquus,FIO)对T2DM大鼠的血糖、血脂及抗氧化作用的影响。结果表明:与模型组相比较,FIO可显著降低T2DM大鼠的空腹血糖(fasting blood glucose,FBG)、促进肝糖原(hepatic glycogen,HGln)合成、改善胰岛素(insulin,INS)抵抗,使总胆固醇(total cholesterol,TC)、甘油三酯(triglyceride,TG)、游离脂肪酸(free fatty acids,FFA)、低密度脂蛋白(low density lipoprotein,LDL)及丙二醛(malondialdehyde,MDA)含量显著下降,高密度脂蛋白(high density lipoprotein,HDL)含量和超氧化物歧化酶(superoxide dismutase,SOD)的活性显著上升。说明FIO能够降低Ⅱ型糖尿病大鼠血糖,改善脂质代谢及氧化应激水平。     

食盐浓度对乳酸菌接种发酵酸笋的影响

为研究食盐浓度对酸笋接种发酵过程的影响,采用柠檬明串珠菌和植物乳杆菌作为混合发酵剂,在不同食盐浓度（0%、1%、3%、5%）条件下发酵制备酸笋。对发酵过程中的乳酸菌、pH、总酸、乳酸、乙酸和亚硝酸盐含量变化进行研究。结果表明,在发酵过程中,1%食盐浓度时乳酸菌数峰值最高（9.65 lg CFU/mL）;发酵120 h时,各食盐浓度组的乳酸菌数量稳定在7.00～7.79 lg CFU/mL之间,pH稳定在3.15～3.39之间,总酸稳定在5.3～6.6 g/L之间;发酵结束时,1%食盐浓度的酸笋中乳酸浓度最高（5.23 g/L）,乙酸含量呈先升高后降低趋势;发酵过程中,亚硝酸盐含量峰值的食盐浓度由大到小依次为0%>1%>3%>5%,发酵120 h时,最终亚硝酸盐含量为3.45～3.90 mg/L,均低于国家标准规定的最大限度。因此,添加1%的食盐有利于酸笋发酵。     

广谱抗菌肽——片球菌素pediocin PA-1

片球菌素PA-1是一种广谱的乳酸菌细菌素,它对食品工业中的腐败菌单核细胞增生李斯特氏菌有强烈的抑制作用,是Ⅱa类细菌素中研究最深入的一种抗菌肽,具有很好的作为食品生物防腐剂开发的应用前景。对近年来关于片球菌素PA-1的结构、作用方式及在食品中的应用作一综述,并对其未来的应用前景,在蛋白质工程、基因工程和化学合成方面进行性质改进做出了展望。     

Pediocin PA-1, a wide-spectrum bacteriocin from lactic acid bacteria

Pediocin PA-1 is a broad-spectrum lactic acid bacteria bacteriocin that shows a particularly strong activity against Listeria monocytogenes, a foodborne pathogen of special concern among the food industries. This antimicrobial peptide is the most extensively studied class Ila (or pediocin family) bacteriocin, and it has been sufficiently well characterized to be used as a food biopreservative. This review focuses on the progress that have been made in the elucidation of its structure, mode of action, and biosynthesis, and includes an overview of its applications in food systems. The aspects that need further research are also addressed. In the future, protein engineering, genetic engineering and/or chemical synthesis may lead to the development of new antimicrobial peptides with improved properties, based on some features of the pediocin PA-1 molecule.     

Comparative Study on Antibacterial Effect of Pediocin ACCEL and Nisin Against Fluorescencestained Listeria monocytogenes BCRC 14845

ABSTRACT: Effects of pediocin ACCEL (Class IIa, pediocin-like bacteriocins) and nisin on carboxyfluorescein diacetate (cFDA) -stained Listeria monocytogenes BCRC 14845 was carried out. Decrease of fluorescence intensity in stained cells and increase in efflux were observed with the increase in bacteriocin concentrations up to 12.5 μg/mL. No further decreases in fluorescence intensity and cell numbers were obtained when the concentration of bacteriocins was over 12.5μg/mL. The leakage of efflux was further confirmed by the release of intracel-lular ultraviolet-absorbing substances. Comparing the leaking time of fluorescence, the intensity of cFDA in nisin-treated cells within 1 min incubation was almost comparable to that in pediocin-treated samples after 40 min incubation. Considering the leakage of cFDA, UV-absorbing substances, changes in cell numbers during incubation of cFDA-stained cells, and restoration ability, nisin seemed to reveal mainly bacteriostatic effect and partially bactericidal effect on L. monocytogenes and to cause easier-to-repair membrane damage. However, pediocin ACCEL appeared to have both bacteriostatic and bactericidal effects on L. monocytogenes and to cause more difficult-to-repair membrane damage.     

Effect of bacteriocin‐producing Pediococcus acidilactici K10 on beer fermentation

Beer is generally considered to be a beverage that has high microbiological stability. However, some undesirable lactic acid bacteria (LAB) can grow in beer and consequently spoil this beverage. In this study, bacteriocin‐producing Pediococcus acidilactici K10 was used as a means of bio‐acidifying the mash and reducing the spoilage LAB content of the beer. The K10 strain had antimicrobial activity against two beer spoilage LAB strains in wort and did not grow in a beer environment. The K10 strain was inoculated before the mashing step. The effect of K10 as a starter culture was investigated and compared with a control. As a result, filtration time was shortened by 17 min, alcohol content was increased by 137%, foam stability was increased by 156%, bitterness was increased by two bitterness units and there was a significant difference (p < 0.05) in aromatic and sour odour. The feasibility of using bacteriocin‐producing LAB strain in beer brewing is envisaged. Copyright © 2016 The Institute of Brewing & Distilling     

Rhodococcus sp.SHZ-1腈水合酶的高酶活发酵工艺

通过研究发酵过程中溶氧、生物量、腈水合酶活力以及残糖的变化规律和搅拌速度、通气量、接种量及诱导剂对产腈水合酶的影响,确立了5L发酵罐中Rhodococcus sp.SHZ-1腈水合酶的高酶活发酵工艺参数。结果表明,发酵过程中溶氧控制在30%以上有利于菌体快速生长和腈水合酶的合成。在pH7.2,温度30℃的发酵条件下,适宜的腈水合酶合成工艺条件为:接种量10%,通气量1.0vvm,搅拌速度采用由初始的200r/min调至500r/min的变速调控方式,同时于48h补加产酶诱导剂,发酵液腈水合酶的最高酶活力达到了9500U/mL,是摇瓶培养时最高酶活力8208U/mL的1.2倍,且比未进行工艺优化时最大产酶期缩短了20～24h,其最佳产酶期为52～60h。     

产细菌素乳酸菌的筛选与鉴定

利用溶钙圈法及牛津杯双层平板法,从欧洲萨拉米香肠、新疆奶酪、自发酵泡菜和韩式辣白菜中分离筛选产细菌素的乳酸菌,通过形态学、生理生化鉴定、16S rDNA将菌株鉴定到种,并对其细菌素基因进行克隆,确定细菌素种类。结果表明:从分离纯化到的206株乳酸菌中筛选出抑菌效果较好的菌株SA102、SA104、N105、N107、N108,在排除酸、过氧化氢等干扰因素后,菌株所产抑菌物质对蛋白酶敏感,初步判定起抑菌作用的是细菌素。16S r DNA结果表明这5株产细菌素的菌株2株为乳酸乳杆菌,3株为植物乳杆菌,通过设计引物对菌株细菌素基因进行PCR快速筛选,结果表明菌株N107、N108含有IIb类细菌素Plantaricin KJ基因编码序列,生理生化指标测试证实这些产细菌素菌株不产气、不产氨、不产硫化氢、不产粘、不产色素,具有较好的生物安全性。最后对发酵液中细菌素粗提物的酸碱稳定性和温度稳定性进行了初步探究,以期为将来细菌素的进一步实际应用提供一定的理论借鉴。      

和田地区酸奶中产细菌素乳酸菌的筛选及细菌素特性的研究

从和田地区酸奶中筛选出了乳酸菌A3,其所产抑菌物质在排除过氧化氢和有机酸的干扰及蛋白酶失活实验后,可以初步确定是一种细菌素。该细菌素对热较稳定,在酸性条件下表现出很好的抑菌活性,同时具有广谱的抑菌活性。根据该菌株的形态和生理生化特性,将A3菌株初步鉴定为肠膜明串珠菌(Leuconostoc mesenteroides)。     

Novel bacteriocins produced by Lactobacillus fermentum strains with bacteriostatic effects in milk against selected indicator microorganisms

The aim of this work was to isolate and characterize bacteriocins produced by 2 Lactobacillus fermentum strains isolated from artisanal Mexican Cocido cheese. Fractions (F ≤3 kDa) obtained from cell-free supernatants of Lb. fermentum strains J23 and J32 were further fractionated by reversed-phase HPLC on a C18 column. Antimicrobial activities of F ≤3 kDa and bacteriocin-containing fractions (BCF), obtained from fractionation of F ≤3 kDa against 4 indicator microorganisms, were determined by the disk diffusion method and growth inhibition in milk. Subsequently, isolated BCF were analyzed by reversed-phase HPLC tandem mass spectrometry. Results showed that BCF presented antimicrobial activity against the 4 indicator microorganisms tested. For J23, one of the fractions (F3) presented the highest activity against Escherichia coli and was also inhibitory against Staphylococcus aureus, Listeria innocua, Salmonella Typhimurium, and Salmonella Choleraesuis. Similarly, fractions F3 and F4 produced by J32 presented antimicrobial activity against all indicator microorganisms. Furthermore, generation time and growth rate showed that F3 from J23 presented significantly higher antimicrobial activity against the 4 indicator microorganisms (2 gram-positive and 2 gram-negative) when inoculated in milk compared with F3 from J32. Interestingly, this fraction presented a broader antimicrobial spectrum in milk than nisin (control). Reversed-phase HPLC tandem mass spectrometry analysis revealed the presence of several peptides in BCF; however, F3 from J23 that was the most active fraction of all presented only 1 bacteriocin. The chemical characterization of this bacteriocin suggested that it was a novel peptide with 10 hydrophobic AA residues in its sequence and a molecular weight of 2,056 Da. This bacteriocin and its producing strain, J23, may find application as a biopreservative against these indicator microorganisms in dairy products.     

Pediococcus acidolactici and Pediococcus pentosaceus isolated from a rainbow trout ecosystem have probiotic and ABF1 adsorbing/degrading abilities in vitro

ABSTRACT

Probiotics are being used in biological control of bacterial pathogens, as an alternative to antibiotics, to improve health and production parameters in fish farming. Fish farming production is severely affected by aflatoxins (AFs), which are a significant problem in aquaculture systems. Aflatoxins exert substantial impact on production, causing disease with high mortality and a gradual decline of reared fish stock quality. Some aspects of aflatoxicosis in fish, particularly its effects on the gastrointestinal tract, have not been well documented. The aim of the present study was to evaluate probiotic properties of lactic acid bacterial (LAB) strains isolated from rainbow trout intestine and feed. Moreover, AFB₁-binding and/or degrading abilities were also evaluated to assess their use in the formulation of feed additives. Growth at pH 2, the ability to co-aggregate with bacterial pathogens, inhibition of bacterial pathogens, and determination of the inhibitory mechanism were tested. Aflatoxin B₁ (AFB₁) adsorption and degradation ability were also tested. All strains were able to maintain viable (10⁷ cells ml^–1) at pH 2. Pediococcus acidilactici RC001 and RC008 showed the strongest antimicrobial activity, inhibiting all the pathogens tested. The strains produced antimicrobial compounds of different nature, being affected by different treatments (catalase, NaOH and heating), which indicated that they could be H₂O_2, organic acids or proteins. All LAB strains tested showed the ability to coaggregate pathogenic bacteria, showing inhibition percentages above 40%. Pediococcus acidilactici RC003 was the one with the highest adsorption capacity and all LAB strains were able to degrade AFB₁ with percentages higher than 15%, showing significant differences with respect to the control. The ability of some of the LAB strains isolated in the present work to compete with pathogens, together with stability against bile and gastric pH, reduction of bioavailability and degradation of AFB₁, may indicate the potential of LAB for use in rainbow trout culture.