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.     

Synergistic and antagonistic effect of lactic acid bacteria on tyramine production by food-borne pathogenic bacteria in tyrosine decarboxylase broth

The effect of lactic acid bacteria (LAB) strains on tyramine (TYR) and also other biogenic amines (BA) production by eight common food-borne pathogen (FBP) in tyrosine decarboxylase broth (TDB) was investigated by using a rapid HPLC method. Significant differences were observed among the FBP strains in ammonia (AMN) and BA production apart from tryptamine, histamine (HIS) and spermine formation (p < 0.05). Salmonella paratyphi A was characterised as the main amine producer. LAB had an important synergetic role in some BA production by food-borne pathogenic bacteria, although the effect of some LAB strains on BA production was strain-dependent. Lactococcus spp. and Streptococcus spp. resulted in significantly higher TYR accumulation by Aeromonas hydrophila and Enterococcus faecalis in TDB. The presence of Lactococcus and/or Lactobacillus in TDB significantly increased HIS production by A. hydrophila, Escherichia coli, Ent. faecalis, Klebsiella pneumoniae and Pseudomonas aeruginosa, whereas HIS accumulation was significantly reduced by Staphylococcus aureus, S. paratyphi A and Listeria monocytogenes.     

Effects of specific lactic acid bacteria species on biogenic amine production by foodborne pathogen

The influences of lactic acid bacteria (LAB) on biogenic amines formation by foodborne pathogens (FBP) were investigated. Biogenic amines production by single and mix cultures was tested in histidine decarboxylase broth. All of the mix cultures (LAB with FBP) inhibited significantly (P < 0.05) the ammonia accumulation except for Escherichia coli with Lactococcus lactic subsp. lactic and Lactobacillus plantarum. Although LAB with most of the pathogen showed considerably stimulation effects on putrescine, cadaverine, spermine, 2‐phenylethylamine, histamine (HIS), tyramine, trimethylamine, dopamine and agmatine (AGM), some of the LAB with pathogens showed poor inhibition effect on different amines formation. HIS production by Klebiella pneumonia was 0.16 mg L^?1, whereas HIS value in presence of Lb. plantarum increased to 30.92 mg L^?1. Consequently, LAB inhibition of the ammonium production by FBP is favourable, while the stimulation effects of LAB on biogenic amines formation by FBPs are not desirable for food industry.     

富硒乳酸菌及其发酵食品的研究进展

乳酸菌作为益生菌中的一个类群,被广泛应用于食品、医药以及化妆品行业。硒,作为人体必需的微量元素之一,在人体新陈代谢及免疫调节方面起到至关重要的作用。近年来,富硒乳酸菌因为其突出的抗氧化性、抗炎症、抗癌活性以及可以将无机硒转化成有利于人体吸收的有机硒而备受关注。然而,乳酸菌对于硒的代谢途径还有待进一步深入研究;同时,对于富硒益生菌及其发酵食品的毒性及副作用也需要更为全面的测试与评估。本文从硒元素的价态、硒对于乳酸菌生长的影响、乳酸菌对硒的有机转化、富硒乳酸菌的生物活性以及富硒功能食品这五个方面对其进行综述。      

乳酸菌在青方腐乳中的应用研究

对从青方腐乳中分离的植物乳杆菌（Lactobacillus plantarum）、短小奇异菌（Atopobium parvulus）和片球菌（Pediococcus）在青方腐乳中的应用进行了研究。结果表明，这3株乳酸菌对青方腐乳的成熟和风味均有一定的促进作用，其中，片球菌对青方腐乳风味的作用效果最好，改变了腐乳中游离氨基酸的含量和呈味特点，并促进大豆蛋白质的水解，降低了腐乳的硬度、坚实性、粘度和黏附性，使腐乳的感官品质得到改善，是改进青方腐乳风味的协同菌株。     

乳酸菌细菌素的高效表达方法研究

乳酸菌细菌素作为天然的生物防腐剂,因其高效、无毒等特点而备受关注,但目前只有乳酸链球菌素实现了工业化生产。乳酸菌细菌素产量低是限制其大规模生产的瓶颈之一。从高产菌株筛选、发酵条件调控、基因工程技术、诱导调控和胁迫刺激应答5个方面,综述了提高乳酸菌细菌素产量的方法,期望为提高乳酸菌细菌素产量的研究提供新思路。     

发酵乳中酵母菌和乳酸菌生长的相互影响

探讨了乳酸菌和酵母菌之间的相互作用。在发酵过程中,酿酒酵母对乳酸菌的生长有抑制作用。乳酸菌能促进酿酒酵母和马克思克鲁维酵母的生长。酿酒酵母和乳酸菌共同接种有利于保持产品冷藏期间活菌数的稳定,菌株之间可能存在共生作用。      

白酒生产中乳酸菌的分布及主要代谢产物

乳酸菌是发酵产乳酸的一类革兰氏阳性菌,是大曲中的主要微生物菌系,对大曲中酯的形成是有利的,但在有些香型白酒(如清香、浓香型白酒)酿造中要控制或降低乳酸菌的作用.该文介绍了白酒生产中乳酸菌的分布,乳酸菌所产主要代谢产物的代谢途径及其对白酒的影响.     

Impact of buffering capacity on the acidification of wort by brewing‐relevant lactic acid bacteria

Acidified wort produced biologically using lactic acid bacteria (LAB) has application during sour beer production and in breweries adhering to the German purity law (Reinheitsgebot ). LAB cultures, however, suffer from end product inhibition and low pH, leading to inefficient lactic acid (LA) yields. Three brewing‐relevant LAB (Pediococcus acidilactici AB39, Lactobacillus amylovorus FST2.11 and Lactobacillus plantarum FST1.7) were examined during batch fermentation of wort possessing increasing buffering capacities (BC). Bacterial growth was progressively impaired when exposed to higher LA concentrations, ceasing in the pH range of 2.9–3.4. The proteolytic rest (50°C) during mashing was found to be a major factor improving the BC of wort. Both a longer mashing profile and the addition of an external protease increased the BC (1.21 and 1.24, respectively) compared with a control wort (1.18), and a positive, linear correlation (R ² = 0.957) between free amino nitrogen and BC was established. Higher levels of BC led to significant greater LA concentration (up to +24%) after 48 h of fermentation, reaching a maximal value of 11.3 g/L. Even higher LA (maximum 12.8 g/L) could be obtained when external buffers were added to wort, while depletion of micronutrient(s) (monosaccharides, amino acids and/or other unidentified compounds) was suggested as the cause of LAB growth cessation. Overall, a significant improvement in LA production during batch fermentation of wort is possible when BC is improved through mashing and/or inclusion of additives (protease and/or external buffers), with further potential for optimization when strain‐dependent nutritional requirements, e.g. sugar and amino acids, are considered. Copyright © 2017 The Institute of Brewing & Distilling     

浅谈乳酸菌在黄酒生产中的作用

为了全面地了解乳酸茵兼在黄酒生产全过程中的作用,介绍了黄酒米浆水中乳酸茵的应用、黄酒深层酿造兼氧浸米中乳酸菌的作用和乳酸菌在黄酒发酵过程中的作用,同时也介绍了乳酸茵代谢产物乳酸和乳酸乙酯在黄酒中的含量和作用。     

Citrulline production by lactic acid bacteria in Chinese rice wine

Ethyl carbamate (EC) is a carcinogenic compound derived from the spontaneous reaction of ethanol with urea or citrulline in Chinese rice wine. Polymerase chain reaction–denaturing gradient gel electrophoresis showed that five species, Lactobacillus fermentum, Lactobacillus plantarum, Lactobacillus brevis, Lactococcus lactis and Lactobacillus coryniformis were the most abundant bacteria in the Chinese rice wine production process. Five strains belonging to these species can degrade arginine primarily in the exponential growth phase and accumulate citrulline in MRS‐Arg medium. In addition, an L. brevis strain was shown to be capable of assimilating citrulline, indicating the potential of this strain suggesting a potential route to reduce citrulline content and ethyl carbamate formation in Chinese rice wine fermentation. Copyright © 2018 The Institute of Brewing & Distilling     

乳酸菌及其代谢产物对肠道炎症的调控作用研究进展

乳酸菌作为一种益生菌,可通过多种方式发挥抗肠炎作用,除了抑制肠道菌群中致病菌的生长和黏附外,还可通过调控肠上皮细胞产生的炎性因子从而发挥抗肠炎作用。本文综述了乳酸菌及其代谢产物对肠道炎症的调节作用,主要介绍了乳酸菌、乳酸菌可溶性物质、DNA、多磷酸盐及其热致死菌体等对肠道炎症的调控作用,并阐明了这些物质发挥抗炎作用的机制。乳酸菌主要是通过抑制NF-κB信号途径和p38 MAPK信号途径进而调节肠道炎症。      

奶啤生产中乳酸菌对酵母菌发酵作用的研究

利用乳酸菌和酵母菌的共生作用,对牛乳进行了混合菌种的发酵研究。分析了共生作用对产品pH值、滴定酸度、乙醇含量和α-氨基酸态氮的影响。研究结果表明,乳酸菌的加入不仅可以提高酵母菌的生长速度,而且可以提高产品的风味,奶啤的酒精含量相对啤酒较低,是酒精度较低的健康型饮料。     

Effects of rare sugar D-allulose on acid production and probiotic activities of dairy lactic acid bacteria

It has recently been reported that the rare sugar d-allulose has beneficial effects, including the suppression of postprandial blood glucose elevation in humans, and can be substituted for sucrose as a low-calorie food ingredient. To examine the applications of d-allulose in the dairy industry, we investigated the effects of d-allulose on the acid production of 8 strains of yogurt starter (Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus) and 4 strains of lactococci, including potential probiotic candidates derived from dairy products. Acid production by 2 L. delbrueckii ssp. bulgaricus yogurt starter strains in milk was suppressed by d-allulose, but this phenomenon was also observed in some strains with another sugar (xylose), a sugar alcohol (sorbitol), or both. In contrast, among the dairy probiotic candidates, Lactococcus lactis H61, which has beneficial effects for human skin when drunk as part of fermented milk, was the only strain that showed suppression of acid production in the presence of d-allulose. Strain H61 did not metabolize d-allulose. We did not observe suppression of acid production by strain H61 with the addition of xylose or sorbitol, and xylose and sorbitol were not metabolized by strain H61. The acid production of strain H61 after culture in a constituted medium (tryptone–yeast extract–glucose broth) was also suppressed with the addition of d-allulose, but growth efficiency and sugar fermentation style were not altered. Probiotic activities—such as the angiotensin-converting enzyme inhibitory activity of H61-fermented milk and the superoxide dismutase activity of H61 cells grown in tryptone–yeast extract–glucose broth—were not affected by d-allulose. d-Allulose may suppress acid production in certain lactic acid bacteria without altering their probiotic activity. It may be useful for developing new probiotic dairy products from probiotic strains such as Lactococcus lactis H61.     

利用纯种乳酸菌制作泡萝卜的技术研究

研究了不同纯种乳酸菌即肠膜明串珠菌、发酵乳杆菌、嗜热链球菌、嗜酸乳杆菌、保加利亚乳杆菌的组合发酵制作泡菜的变化和风味。结果表明,与传统发酵制作工艺相比,嗜酸乳杆菌+肠膜明串珠菌+发酵乳杆菌组合发酵(添加量为发酵液的5%),发酵速度快、产品风味好、亚硝酸盐含量为0.385×10-6mg/kg低于传统工艺生产的产品(1.55×10-6mg/kg),产品质量稳定。     

臭豆腐乳酸菌多样性及耐酸乳酸菌的筛选分离

对采集的8个不同地区的臭豆腐样品中的乳酸菌多样性分析表明,臭豆腐中乳酸菌数量在6.8×104cfu/g～2.9×106cfu/g,优势乳酸菌包括乳杆菌、乳球菌和肠球菌.通过乳酸菌耐酸特性比较,表明不同来源样品中乳酸菌耐酸差异性不明显,而不同种类乳酸菌的耐酸差异性较明显,肠球菌耐酸性比例高,乳杆菌其次,乳球菌最低.经筛选获得pH 3.0、37℃培养6 h后存活率超过30%的菌株6株,对其中2株耐酸最强的杆菌和球菌进行鉴定,分别为植物乳杆菌和屎肠球菌.     

发酵肉制品中乳酸菌的主要发酵特性

从发酵肉制品中分离、纯化乳酸菌132株,对它们的主要发酵特性如耐盐性、耐硝性、产黏液、产气等进行了测定,并比较了它们在不同培养基中的产酸情况。     

功能性乳酸菌的应用研究

乳酸菌是一类宝贵的微生物资源。本文介绍了乳酸菌的免疫、抗氧化、降胆固醇、抗高血压、改善风味、抗菌等功能及其应用技术,为进一步的开发利用提供参考。