Nutritional factors affecting the production of two bacteriocins from lactic acid bacteria on whey

The ability of Lactococcus lactis subsp. lactis CECT 539 and Pediococcus acidilactici NRRL B-5627 to produce bacteriocins on both diluted and concentrated whey was investigated in batch fermentations. Both strains produced the higher amounts of biomass and bacteriocin titres on diluted whey. Luedeking and Piret expression was able to model the production of nisin, which was produced as a primary metabolite on both culture media. However, the pediocin production could not be typified in any case due to the negligible growth of P. acidilactici. Although the whey supported the growth and bacteriocin production by the two strains, both biomass and bacteriocin productions were lower than those obtained on MRS broth. The effect of total sugar, nitrogen, phosphorous and buffer concentrations on the production of nisin and pediocin was studied in diluted whey using factorial experiments and empirical modelling. The production of nisin was greatly inhibited by the increase in nitrogen, buffer, and to a lesser extent, sugar concentration in the medium, nevertheless, the used phosphorous source produced a light stimulatory effect on bacteriocin synthesis. In addition, the growth of Lc 1.04 was mainly affected by the nitrogen source used. On the other hand, pediocin was inhibited by the increase in buffer, phosphorous, and to a lesser degree, by the sugar and nitrogen concentration.

The inhibitory activity of pediocin disappeared almost totally after 15 min of treatment with trypsin, papain, subtilisin and pepsin. The activity of nisin was drastically reduced by treatment with trypsin, subtilisin and pepsin. Nevertheless, 50% of the initial activity was retained when nisin was treated with papain. Both bacteriocins showed the highest heat stability at acidic pH and short incubation times.     

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.     

Antimicrobial activity of pediocin PA-1 against Oenococcus oeni and other wine bacteria

Pediocin PA-1 is an antimicrobial peptide produced by lactic acid bacteria (LAB) that has been sufficiently well characterised to be used in food industry as a biopreservative. Sulphur dioxide is the traditional antimicrobial agent used during the winemaking process to control bacterial growth and wine spoilage. In this study, we describe the effect of pediocin PA-1 alone and in combination with sulphur dioxide and ethanol on the growth of a collection of 53 oenological LAB, 18 acetic acid bacteria and 16 yeast strains; in addition, production of pediocin PA-1 by Pediococcus acidilactici J347-29 in presence of ethanol and grape must is also reported. Inhibitory concentrations (IC) and minimal bactericide concentrations of pediocin PA-1 were determined against LAB, and revealed a bacteriostatic effect. Oenococcus oeni resulted more sensitive to pediocin PA-1 (IC₅₀ = 19 ng/ml) than the other LAB species (IC₅₀ = 312 ng/ml). Cooperative inhibitory effects of pediocin PA-1 and either sulphur dioxide or ethanol were observed on LAB growth. Moreover, the pediocin PA-1 producing P. acidilactici strain J347-29 was able to grow and produce the bacteriocin in presence of ethanol (up to 4% ethanol in the fermentation broth) and grape must (up to 80%), which indicated that pediocin PA-1 can be considered as a potential biopreservative in winemaking.     

Incidence of lactic acid bacteria and Aspergillus flavus in brewer's grains and evaluation of potential antifungal activity of these bacteria

Feed destined for animal production as brewer's grains can be contaminated by Aspergillus section Flavi species. Lactic acid bacteria (LAB) play a defining role in the preservation and microbial safety of fermented foods. The objective of this study was to study the incidence of lactic acid bacteria, Aspergillus section Flavi and AFB₁ in brewer's grains and the preliminary antifungal activity of native LAB in vitro. LAB and aflatoxigenic Aspergillus were found in high counts in brewer's grains used as raw material for pig feedstuff. However, AFB₁ had low AFB₁ natural incidence in samples. In vitro antifungal activity of LAB isolated showed that all bacteria tested inhibited two Aspergillus flavus strains assayed. The high incidence of LAB could be inhibiting the AFB₁ production in by-products obtained from the beer industry. LAB strains with excellent antimicrobial activity were also found in this substrate.     

乳酸菌抗真菌活性及其抑制真菌毒素的效果

讨论了乳酸菌抗真菌的活性及其清除真菌毒素的3种可能机制，即①乳酸菌通过对霉菌生长的直接抑制，从而抑制真菌毒素的形成；②通过产生代谢产物抑制真菌菌株或降解真菌毒素到无毒或毒性较低的化合物，以此降低真菌毒素的危害；③借助乳酸菌细胞壁与真菌毒素(黄曲霉毒素B1和玉米赤霉烯酮)的物理结合来清除介质中的毒素危害。乳酸菌的抗真菌活性和清除霉菌毒素的能力显然受到菌株、细胞浓度、细胞处理方式和环境条件的影响。新型发酵乳菌株筛选过程中应该考虑乳酸菌菌株的抗真菌活性及其清除真菌毒素的能力。     

乳酸菌抗氧化活性的研究进展

介绍了乳酸菌的抗氧化活性、可能机制及其研究进展。在体外实验中，乳酸菌及其无细胞提取物能清除机体羟自由基(HO)、过氧化氢(H2O2)、二苯代苦味肼基自由基(DPPH)；可抑制脂质过氧化、螯合金属离子，具有总还原能力及SOD酶活性。并介绍了乳酸菌抗氧化活性的体内实验结果。     

乳酸菌抗突变活性的研究进展

根据近年来国内外报道，对乳酸菌抗突变活性的研究进展进行了综述，并介绍了乳酸菌抗突变活性物质的分离、纯化及其研究方法。     

乳酸菌Ⅱ类细菌素生物合成及其代谢调控策略

乳酸菌细菌素是乳酸菌经由核糖体合成的具有抑菌活性的多肽类物质,其中乳酸菌Ⅱ类细菌素具有很强的热稳定性和抑菌活性,但是产量较低尚不能实现商业化生产。因此,了解和掌握乳酸菌Ⅱ类细菌素合成及其代谢调控机制,对解决商业化生产过程的技术瓶颈具有重要的意义。该文综述了目前Ⅱ类细菌素生物合成和降解途径,并从代谢调控角度提出提高Ⅱ类细菌素产量的可行性策略,为提高Ⅱ类细菌素产量提供新的途径和思路,也为Ⅱ类细菌素工业化生产奠定基础。     

抗真菌乳酸菌研究

食品安全是近年来公众关注的焦点,常规的食品防腐剂由于其可能的致癌致畸副作用,促使人们寻找可替代的天然安全防腐剂。乳酸菌具有充当天然防腐剂的潜质和优势,其抗真菌研究是当前研究的热点。人们经过研究发现乳酸菌可以产生有机酸、肽类及脂肪酸等抗真菌类物质。本文就当前抗真菌乳酸菌研究进行综述,对不同抗真菌物质进行详细阐述,并对后续研究进行展望。     

活性乳酸菌制品中乳酸菌计数培养条件探讨

为快速、准确地计数活性乳酸菌制品中的乳酸菌，用CO2烛缸法代替现行国家标准GB／T16347－1996活性乳酸菌饮料中乳酸菌微生物检验方法中的有氧培养法，CO2烛缸法操作简便，计算准确可靠，在菌种对比实验中，CO2烛缸法的乳酸菌计数结果是国家标准方法的8倍，在试样的对比实验中，CO2烛缸法的乳酸菌计数结果是国家标准方法的20倍，CO2烛缸法较目前国家标准方法更能真实施反映活性乳酸菌制品中乳酸菌的数量。     

Biocontrol of Listeria monocytogenes by lactic acid bacteria isolated from brewer's grains used as feedstuff in Argentina

Brewer's grains are the most important by-product of the brewery industry and it is mostly used as a protein and energy source in animal nutrition. Listeria monocytogenes is a food-borne pathogen can cause invasive diseases such as meningoencephalitis, sepsis, abortion, and gastroenteritis in humans and several animal species. The aim of this work was to study the antilisterial activity of lactic acid bacteria (LAB) isolated from brewer's grains. The incidence of Listeria spp. in brewer's grains was 3.12%. Twenty-one LAB inhibited the growth of the eight strains of L. monocytogenes. The mean inhibition halo of cell free supernatants of LAB ranged between 11.5 and 24.5 mm. The isolation of lactic acid bacteria with antilisterial activity from brewer's grains is promising based on their capacity to produce antimicrobial compounds. The production of antimicrobial metabolites by LAB in the substrate would generate an unfavorable environment for the growth of the pathogenic bacterium under study.     

Combating biofilms of foodborne pathogens with bacteriocins by lactic acid bacteria in the food industry

Most foodborne pathogens have biofilm-forming capacity and prefer to grow in the form of biofilms. Presence of biofilms on food contact surfaces can lead to persistence of pathogens and the recurrent cross-contamination of food products, resulting in serious problems associated with food safety and economic losses. Resistance of biofilm cells to conventional sanitizers urges the development of natural alternatives to effectively inhibit biofilm formation and eradicate preformed biofilms. Lactic acid bacteria (LAB) produce bacteriocins which are ribosomally synthesized antimicrobial peptides, providing a great source of nature antimicrobials with the advantages of green and safe properties. Studies on biofilm control by newly identified bacteriocins are increasing, targeting primarily onListeria monocytogenes, Staphylococcus aureus, Salmonella, and Escherichia coli. This review systematically complies and assesses the antibiofilm property of LAB bacteriocins in controlling foodborne bacterial-biofilms on food contact surfaces. The bacteriocin-producing LAB genera/species, test method (inhibition and eradication), activity spectrum and surfaces are discussed, and the antibiofilm mechanisms are also argued. The findings indicate that bacteriocins can effectively inhibit biofilm formation in a dose-dependent manner, but are difficult to disrupt preformed biofilms. Synergistic combination with other antimicrobials, incorporation in nanoconjugates and implementation of bioengineering can help to strengthen their antibiofilm activity. This review provides an overview of the potential and application of LAB bacteriocins in combating bacterial biofilms in food processing environments, assisting in the development and widespread use of bacteriocin as a promising antibiofilm-agent in food industries.     

Reduction of Escherichia coli population following treatment with bacteriocins from lactic acid bacteria and chelators

The inhibitory activity of lactocin 705/AL705 (2133 arbitrary units per ml (AU ml(-1))), two bacteriocins produced by Lactobacillus curvatus CRL705 and nisin (1066AU ml(-1)) produced by Lactococcus lactis CRL1109 in combination with chelating agents against Escherichia coli strains in TSB medium at 21 and 6 degrees C was investigated. Treatment with EDTA (500 and 1000 mm) and Na lactate (800 mm) alone produced a variable effect depending on the strain, Na lactate being inhibitory against E. coli NCTC12900 at both assayed temperatures while EDTA (1000 mm) led to its inactivation only at 6 degrees C. Direct and deferred strategies using EDTA and Na lactate showed that the direct addition of bacteriocins and chelators was not as effective as compared to deferred treatments. When the deferred treatment effectiveness was evaluated at 6 degrees C, the use of EDTA (500 and 1000 mm) and Na lactate (800 mm) in combination with lactocin 705/AL705 demonstrated to be the most inhibitory strategy against both E. coli strains. Nevertheless, treatments with chelators and bacteriocins was highly dependent upon strain sensitivity. Permeabilization of the outer membrane of E. coli strains with EDTA and Na lactate combined with lactocin 705/AL705 showed to be valuable in controlling this foodborne bacteria at low temperatures.     

具有抑菌作用乳酸菌筛选及其在红酸汤生产中的应用

目的 筛选具有抑菌作用的乳酸菌并研究其在红酸汤的加工和保藏中的应用。方法 以热带假丝酵母CT-1和白色假丝酵母CU-3为红酸汤腐败指示菌,筛选具有抑菌能力的乳酸菌,然后将乳酸菌用于红酸汤的加工探讨其生物防腐作用。结果 经筛选获得两株具有抑菌作用的乳酸菌分别为植物乳杆菌SHPC-35和耐酸乳杆菌SHC-17,且两株菌的主要抑菌物质均为细菌素。将两株菌用于红酸汤的生产,并确定最优发酵工艺为：接种量（乳酸菌SHPC-35和SHC-17复配比例为1:1）为3%,发酵温度为28℃,发酵时间为4d,在此条件下,红酸汤的总酸度为1.58±0.03%,感官评分为92.35±6.11。红酸汤保藏试验结果表明,SHPC-35和SHC-17能抑制红酸汤中的酵母生长,从而有效地延长产品的货架期至10 d。结论 植物乳杆菌SHPC-35和耐酸乳杆菌SHC-17具有较强的抑制热带假丝酵母CT-1和白色假丝酵母CU-3能力,在红酸汤以及其他发酵食品的生物防腐方面具有一定的应用潜力。。     

乳酸菌细菌素抑菌特性及在食品中的应用研究进展

乳酸菌细菌素是细菌在核糖体上合成的具有抗菌活性的多肽类物质,这些细菌素能杀灭或抑制引起食品腐败的细菌的繁殖,可作为天然的食品防腐剂在食品中应用。该文综述了乳酸菌细菌素的分类、国内外研究现状、抑菌特性及应用等方面的最新研究进展,并对乳酸菌细菌素未来研究趋势进行简要分析,对乳酸菌细菌素在食品中的应用有一定参考价值。     

抗幽门螺杆菌乳酸菌的筛选

通过测定干酪乳杆菌（Lactobacillus casei）的自凝聚、疏水性及抑菌实验来筛选粘附性高、对幽门螺杆菌（Helicobacter pylori）有强抑制作用的益生菌株,并通过干酪乳杆菌与幽门螺杆菌的交互凝集和对幽门螺杆菌尿素酶活性的抑制进一步探讨其抑菌机制。结果表明,在4株干酪乳杆菌中,菌株JY300-8的自凝聚百分比在24 h达到71.7%,比菌株JY、JY160-15、JY300-10分别高19.7%、28.8%、29.6%（P＜0.05）;疏水性百分比为72.3%,比菌株JY、JY160-15、JY300-10分别高4.1%、8.0%、7.5%（P＜0.05）。同时,菌株JY300-8在24 h时的共凝集百分比为64.4%,较菌株JY提高了5.3%;而且菌株JY300-8对幽门螺杆菌尿素酶活性的抑制率达到62.3%。结果表明,在4株干酪乳杆菌中,菌株JY300-8具有良好的益生性能,对胃癌的生物致病菌具有良好的抑制效果,可用于后续胃癌动物模型的研究和抗胃癌的益生菌制剂的开发。     

高抗氧化活性乳酸菌的筛选

比较了15株乳酸菌的抗氧化能力,旨在筛选出高抗氧化活性的乳酸菌,为天然抗氧化剂的开发及乳酸菌在功能性食品中的应用提供理论依据。通过羟自由基清除试验、超氧阴离子自由基清除试验以及还原能力评价试验,系统评价了15株受试乳酸菌的菌体及其胞外分泌物的抗氧化能力。结果表明,抗氧化活性具有显著的菌株特异性。菌株L14（植物乳杆菌）在上述3种评价体系中均表现出最强的抗氧化能力,其次是菌株L15（唾液乳杆菌）,表明这两株乳酸菌在减轻机体氧化损伤方面具有一定的应用价值。     

Production of pyroglutamic acid by thermophilic lactic acid bacteria in hard-cooked mini-cheeses

Pyroglutamic acid is present in high amounts (0.5g/ 100g) in many cheese varieties-and particularly in extensively ripened Italian cheeses such as Grana Padano and Parmigiano Reggiano. An in vivo model system for cooked mini-cheese production and ripening acceleration was set up to demonstrate the ability of thermophilic lactic acid bacteria, used as a starter, to produce pyroglutamic acid (pGlu). In mini-cheeses stored at 38 and 30 degrees C for up to 45 d, all starters tested produced different amounts of pGlu. In descending order of pGlu production, the bacteria analyzed were: Lactobacillus helveticus, Lactobacillus delbrueckii subsp. bulgaricus, Streptococcus thermophilus, and Lactobacillus delbrueckii subsp. lactis. Evidence for the presence of glutamine to pGlu cyclase activity in lactic acid bacteria was provided. Cell lysates obtained from cultures of L. helveticus, L. delbrueckii subsp. bulgaricus, L. delbrueckii subsp. lactis, and S. thermophilus showed the ability to cyclize glutamine to pGlu, resulting in processing yields from 1.4 to 30.3%, depending on the subspecies. Formation of pGlu from free glutamine appeared to be similar to that observed using a glutamine-glutamine dipeptide substrate. Under the experimental conditions applied, pGlu aminopeptidase activity was only detected in L. helveticus. Thus, pGlu formation in long-ripened cooked cheese may depend on the activity of thermophilic lactic acid bacteria.