Antimicrobial Profile of Lactic Acid Bacteria Isolated from Vegetables and Indigenous Fermented Foods of India against Clinical Pathogens Using Microdilution Method

In dairy and food industries lactic acid bacteria （LAB） have been used in form of starter culture that plays vital role in fermentation; as flavouring and texturizing or as preservative agents. There is increasing evidence that lactobacilli which inhabit the gastrointestinal tract develop antimicrobial activities and participate in the host＇s defence system[1]. During fermentation, most of the LAB produces a number of different compounds like organic acids, hydrogen peroxide, diacetyl, acetaldehyde, carbon dioxide, polysaccharides, and proteinaceous compounds called bacteriocins or bacteriocinogenic peptides.

Predominant Lactic Acid Bacteria Involved in the Traditional Fermentation of <i>Fufu</i>and <i>Ogi</i>, Two Nigerian Fermented Food Products

Traditional methods of preparation were simulated in the laboratory fermentations of cassava and maize to produce fufu and ogi respectively. Changes in pH, temperature and titratable acidity, as well as the diversity of lactic acid bacteria species were investigated during both fermentations. Lactic acid bacteria strains involved in the fermentation processes were isolated at twelve hourly intervals, characterized and identified using phenotypic and biochemical methods. A rapid decrease in pH, 5.6 to 3.7 in fufu and 5.9 to 3.8 in ogi, were observed with temperature increasing from 26℃?to 30℃and 25℃?to 31℃?in fufu and ogi respectively. Most of the lactic acid bacteria strains isolated were homofermentative and heterofermentative Lactobacillus species and heterofermentative Leuconostoc species. Lactobacillus plantarum and Leuconostoc mesenteroides were the dominant lactic acid bacteria species in fufu while L. cellobiosus, L. plantarum and Lc. lactis were dominant in ogi fermentation. An ecological succession pattern in which Leuconostoc species were mostly isolated during early stages of fermentation with the final stages populated with Lactobacillus species was observed in both cases and is attributable to differential acid tolerance of the two genera. The frequencies of dominance of the strains in fufu were L. plantarum (56.25%), Lc. mesenteroides (18.75%), L. lactis (6.25%), L. coprophillus (6.25%), L. acidophilus (6.25%) and L. brevis (6.25%). The frequencies of dominance in ogi were L. cellobiosus (26.6%), Lc. lactis (26.6%), L. plantarum (20.0%), L. acidophilus (13.33%) and Lc. paramesenteroides (13.33%). The dominant strains can serve as potential starter cultures for fufu and ogi production.

Application of Metabonomics in the Research of Lactic Acid Bacteria-fermented Foods

Lactic acid bacteria have been important industrial floras in the food fermentation production industry since ancient times.Their metabonomics technology has been widely used in the process monitoring,product classification and flavor formation mechanism of lactic acid bacteria-fermented foods.In this study,we discussed the application status of metabonomics technology in lactic acid bacteria-fermented food industry and scientific research,including dairy products,soy products,beverages and some pickled foods.Metabolomics will be applied in the research fields of lactic acid bacteria metabolism mechanism of lactic acid bacteria-fermented foods,lactic acid bacteria metabolomics database construction and expansion,metabolomics and genomics,and proteomics.In particular,the metabolomics technology will be introduced into product development and quality monitoring of traditional Chinese lactic acid bacteria-fermented foods,such as fermented bean curd and suancai,thereby perfecting industry norms and improving the level of industry development.

3D printed lactic acid bacteria hydrogel:cell release kinetics and stability

In this study,a new type of 3 D printed living biological hydrogel was developed by integrating lactic acid bacteria(LAB)into biocompatible and non-toxic polymer materials.Interestingly,the living materials loaded with LAB can be freeze-dried and reused for more than 100 times.The bio-hydrogel can be used to co-culture different LAB and keep its fermentation performance stable in long-term use.The release kinetics model and response surface method were used to simulate and optimize the bacteria release mode in the bio-hydrogel.The results show that the release of bacteria from hydrogel is regulated by the coupling of Fickian diffusion and polymer swelling.The stability of LAB hydrogel was evaluated by reuse experiments.The images of confocal microscopy and scanning electron microscope showed that the bacteria with high cell viability were distributed in the hydrogel and intact structure of the living hydrogel was maintained after 100 times of reuse as yoghurt starter.In conclusion,the 3 D printed LAB bio-hydrogel developed in this study has the advantage of reuse and sustainability,which is expected to open up a new way for the preparation of food culture starter.

Health-promoting microbes in traditional Vietnamese fermented foods:A review

Vietnam has a long history of numerous traditional fermented products that contain a range of microorganisms with favorable technological,preservative,and organoleptic properties for food processing as well as other functional properties.This review emphasizes the most common traditional Vietnamese fermented foods and their beneficial indigenous bacteria having health-promoting effects.

More than a Few LAB Alleviate Common Allergies: Impact of Paraprobiotics in Comparison to Probiotical Live Cells

The evidence in this paper indicates that the alarming increase of common allergies can be reduced by the intake of particular “probiotics” or “paraprobiotics” along with food. This appears to build a consensus in the pharmaceutical and food communities about the role of probiotics in the prevention and treatments of common allergies. Food allergy is one of the common allergies, defined as an adverse health effect arising from a specific immune response that occurs reproducibly on exposure to a given food. Improving the digestion of foods and maintaining a healthy gastrointestinal (GI) tract is certainly critical to controlling food allergens. Therefore, the association between a leaky gut or an impaired intestinal permeability and food-allergenic reactions is explained. Gluten has been found to be somehow a justification for protein allergy, and should, therefore, be avoided by people with celiac disease. In several, in vitro models, surface layer (S- layer) proteins of selective paraprobiotics have shown potential in alleviating food allergies and intestinal disorders. Notably, lactobacilli paraprobiotics have proven to be the immediate immunomodulators against common allergies and other diseases, including viral (flu, hepatitis C), bacterial (bronchitis), asthma, chronic fatigue, fibromyalgia, gastrointestinal distress, and autism disorders in humans.

Antifungal activity of lactic acid bacteria isolated from kunu-zaki,a cereal-based Nigerian fermented beverage

Fungal deterioration is a barrier to the wide acceptance of fermented cereal foods from Africa.The use of protective cultures is a natural approach to controlling fungi in foods that also complies with a clean label strategy.This study aims to select antifungal lactic acid bacteria(LAB)previously isolated from kunu-zaki to bio-control deterioration in this cereal-based Nigerian fermented beverage.Strains of Leuconostoc citreum(1),Limosilactobacillus fermentum(6),and Weissella confusa(3)were the most active against seven test mold species,with average inhibition score of 2.25-2.88,after screening 220 LAB strains using agar overlay on millet-sorghum flour hydrolysate(MSFH)agar.The MSFH agar diffusion method revealed that antifungal activity against the seven target molds was retained in cell-free supernatants(CFSs)of selected LABs,with the strongest inhibition against A.flavus F008BA and P.citrinum 3AS1 demonstrated by L.fermentum 5KJEU5(9.06%)and W.confusa YKDIA1(24.55%),respectively.The antifungal activity of CFSs was mainly due to the occurrence of acidic compounds,with the most abundant compounds being acetic(0.30-1.96 mg/mL)and lactic(1.80-3.23 mg/mL)acids.Other compounds such as hydroxycaffeic(0.16-6.72μg/mL),3-(4-hydroxyphenyl)propionic(1.40-6.36μg/mL),3-phenyllactic(1.28-24.48μg/mL),and hydroxyferulic acids(12.25μg/mL)occurred at lower concentrations.In challenged kunu-zaki,L.fermentum 5KJEU5 prevented the growth of A.flavus F008BA and P.citrinum 3AS1 beyond 8 day at ambient temperature(25◦C).In this study,LAB from kunu-zaki displayed strong antifungal activity,showing great potential as a protective culture to prevent fungal growth and mycotoxin accumulation in cereal foods.

Impact of lactic acid bacteria on the control of Listeria monocytogenes in ready-to-eat foods

Due to the increased demand for ready-to-eat(RTE)minimally processed foods,alternatives to chemical and thermal preservation methods to maintain food safety are highly demanded.A significant safety hazard in RTE food products is the growth of the foodborne pathogen Listeria monocytogenes(L.monocytogenes).After processing,recontamination or cross-contamination of L.monocytogenes in RTE food products may occur and the lack of cooking can lead to an increased risk of listeriosis.Further,some RTE food products(e.g.cheese and cured meat)can have a long processing period and shelf life,thus allowing for the growth and proliferation of L.monocytogenes in the food matrix.Lactic acid bacteria(LAB)are generally recognized as safe probiotics and have been proposed as a biological control approach to eliminate foodborne pathogens including L.monocytogenes.LAB have been reported to extend the shelf life of food products and inhibit pathogen proliferation via growth competition and metabolite production.LAB are native microflora of many RTE foods,but only certain LAB may inhibit pathogen growth.Therefore,the specificity of LAB species should be employed in their use in RTE foods.This review will discuss the antimicrobial mechanisms of LAB against L.monocytogenes,selective use of LAB in food matrices,and their uses in food processing and packaging.

Lactic acid bacteria as pro-technological,bioprotective and health-promoting cultures in the dairy food industry

Lactic acid bacteria (LAB) constitute pivotal microorganisms for the food industry due to their considerable technological and functional potential.Fermented dairy products,that is ancient traditions worldwide,still have been accepted and consumed today for their nutritional and organoleptic attributes.In accordance with the current trends in the market and greater awareness of consumer well-being,a detailed assessment of the health effects of dairy product consumption has been undertaken with particular reference to the production of bioactive metabolites including i.e.,γ-aminobutyric acid,conjugated linoleic acid,bioactive peptides,exopolysaccharides as well as vitamins during LAB fermentation.The long histories of yogurt,kefir,and traditional fermented milk drink as sources of some certain probiotic bacteria as well as the opportunity to bio-fortify the matrix with bioactive microbial compounds in situ make fermented dairy products an attractive model in the efforts to develop sustainable functional food systems.Therefore,this review provides the main biochemical characteristics and biotechnological application of LAB as pro-technological,bioprotective,and health-promoting in the food chain.

Natural populations of lactic acid bacteria in douchi from Yunnan Province,China

This research was aimed at isolating and identifying the predominant lactic acid bacteria(LAB) in the traditional Chinese salt-fermented soybean food,douchi,from Yunnan,China.The predominant LAB present were isolated and identified by conventional culture-dependent methods combined with molecular biological methods.Two hundred and sixty isolates were obtained from thirty kinds of traditional fermented douchi from six cities and counties in Yunnan,and those strains were divided into twelve groups by their morphological and biochemical characteristics.Based on 16S ribosomal DNA(rDNA) sequencing and analysis,56 representative strains were identified as belonging to 6 genera and 14 species:Lactobacillus(4 spp.),Weissella(3 spp.),Pediococcus(2 spp.),Staphylococcus(2 spp.),Enterococcus(1 sp.),and Bacillus(2 spp.).The results show that douchi contains a large natural population of LAB of diverse composition from which some strains could be selected as starters for functional fermented foods.This is the first study on the original douchi from Yunnan,and the results suggest that it may be a useful source for the isolation of LAB.This study has also laid a foundation for further research on developing functional douchi products.

An overview of plant-autochthonous microorganisms and fermented vegetable foods

Fermented plant-based foods and beverages constitute foods of high nutritional and functional value with appreciated health beneficial effects.They represent a natural and sustainable alternative to counteract the large wastage of vegetables and fruits due to their short shelf life.Usually,the use of controlled fermentation process using autochthonous microorganisms adapted to their vegetable matrix is preferred instead of traditionally spontaneous fermentation to designing fermented vegetable foods with the desirable sensory,technological,nutritional and functional properties.This review summarizes the autochthonous microorganisms selected as starters for the successful fermentation of vegetables and fruits.The main beneficial properties of autochthonous starters and fermented vegetable products with a focus on human health are revised.

Recent developments in dairy kefir-derived lactic acid bacteria and their health benefits

Kefir is one of the most consumed traditional fermented dairy products and it has a complex probiotic and nutritional composition.Kefir grain contains casein and other milk solids together with the yeasts and lactobacilli that cause the characteristic kefir fermentation and serve as a starter to induce this fermentation when introduced into fresh milk.Both kefir and kefir grains have a rich microbiota and their composition is affected by many parameters like kefir origin,production method(artisanal or industrial),kefir grain:milk ratio,type of milk,fermentation conditions,inoculum source,equipment used in production and storage conditions.Lactic acid bacteria(LAB)are a significant part of the kefir’s microbial composition and the health-promoting effects.Kefir-derived LAB have beneficial effects on colorectal cancer,cardiovascular diseases,type 2 diabetes mellitus,obesity,kidney diseases,modulation of the immune system as well as intestinal microbiota through different biological mechanisms.In addition,bioactive peptides and metabolic products of kefir have shown promising results as health beneficial components along with certain antiviral effects including COVID-19.Therefore,this article is up-to-date information about the production,processing as well as health benefits of dairy kefir-derived LAB with future prospect of work.

乳酸菌抗氧化机制研究进展及在食品领域的应用

乳酸菌不仅有助于改善发酵食品的风味,提高营养价值,还有助于预防由于氧化反应而引发的多种疾病。这些有益功能的发挥与乳酸菌的抗氧化活性密不可分。本文详细阐述了乳酸菌的抗氧化机制,包括调节抗氧化酶类、调控信号通路、清除自由基系统、抑制脂质过氧化作用及金属离子螯合作用;总结了乳酸菌的抗氧化特性在乳制品、肉制品、水产品和果蔬制品等领域的应用现状;概述了乳酸菌抗氧化活性的体外和体内评估方法,旨在为乳酸菌在食品加工领域的深层次应用提供相关参考。

乳酸菌在酱类开封后腐败控制中的应用研究

为研究乳酸菌对酱类食品开封取用过程中腐败控制的作用,探究了乳酸菌的耐盐、抑菌能力及其在模拟家庭开封取用过程中对酱中乳酸菌活菌数、细菌菌落总数、细菌群落组成及产生不愉快气味的主要挥发性成分的影响。结果表明:植物乳杆菌可耐受质量分数7%的NaCl,且具有较强的抑菌能力;在模拟酱的家庭取用过程中,植物乳杆菌可有效抑制酱中的细菌菌落总数并保持乳酸菌活菌数的稳定;添加植物乳杆菌的酱中Lactobacillus的相对丰度为83.6%,可以维持Lactobacillus为酱中的优势属;产生不愉快气味的主要挥发性成分的相对质量分数仅为空白对照的4.71%,可有效抑制酱中不愉快气味的产生。因此,植物乳杆菌可延长酱类食品在家庭取用过程中的实际保质期,在食品绿色防腐中具有潜在的应用前景。

可缓解食物过敏的热灭活乳酸菌的筛选及其全基因组分析

食物过敏(FA)是指人体免疫系统对特定食物产生的异常反应,会导致消化道、呼吸道、皮肤和心血管系统等多个系统的不适。本文通过透明质酸酶抑制试验和RBL-2H3细胞试验,从20株乳酸菌中筛选出抗过敏活性较强的热灭活副干酪乳杆菌JY56。随后,通过全基因组测序和体外安全性试验,评价副干酪乳杆菌Y56菌株的安全性。最后,构建卵清蛋白(OVA)诱导的FA小鼠模型,明确HK-副干酪乳杆菌JY56对FA小鼠临床症状的缓解效果。结果表明,HK-副干酪乳杆菌JY56具有较高的β-氨基己糖苷酶(β-HEX)抑制率,其干预后细胞因子IL-4、IL-5、IL-13、TNF-α的含量显著降低。全基因组学测序分析发现副干酪乳杆菌JY56不具有毒性和传递接收抗生素耐药基因的能力。抗生素敏感性试验、溶血试验、有害代谢产物评价等安全性评价试验表明副干酪乳杆菌JY56对常用抗生素具有敏感性,不产生溶血作用和有害代谢产物。上述说明副干酪乳杆菌JY56具有安全性,其灭活菌体可用于后续研究。OVA刺激后会导致小鼠的体质量和直肠温度降低,过敏评分提高,而HK-副干酪乳杆菌JY56干预后可以明显缓解小鼠过敏症状。本研究结果为HK-副干酪乳杆菌JY56用于缓解食物过敏及相关疾病提供理论依据。

后生元的作用机制及其在食品领域的应用

后生元是由对宿主健康有益的无生命的微生物细胞和/或其成分,以及其代谢产物制成的微生态制剂。后生元具有调节肠道菌群平衡、增强免疫力、抗炎抗菌等功效。与由活性细胞组成的益生菌相比,后生元更安全、更稳定、更有效和更方便。本文概述了后生元的由来、来源菌株、制备途径及其优点,并与益生菌进行对比,阐述了后生元的作用机制。此外,本文从功能性食品补充剂、食品品质改良剂、食品防腐剂以及食品脱毒剂4个方面介绍后生元在食品的应用。相信随着后生元的定义、分类、作用成分变得更加清晰,它将会更广泛地应用于普通食品、营养保健品、特殊医学食品、婴幼儿食品和个护日化产品等领域,还将推动一系列基础科学与应用科学的跨越式发展。

市售发酵食品中乳酸菌的耐药性评估及传播风险研究

为评估发酵食品中乳酸菌的耐药性及其传播风险,作者对市售酸奶和泡菜中的乳酸菌进行分离鉴定。以纸片扩散法鉴定其耐药表型,分析多重耐药情况,PCR鉴定其耐药基因型。从40份样品中共分离得到包括9种不同种属在内的62株乳酸菌,其中酸奶源乳酸菌均为多重耐药菌,对卡那霉素等5种抗生素的耐药率均高于泡菜源菌株,而泡菜源乳酸菌对庆大霉素和链霉素的耐药率均在40%以上。耐药基因型鉴定结果表明,tetM的检出率最高,为16.12%,酸奶样品分离株中有5种基因的检出率高于泡菜样品。2株酸奶源菌株中四环素耐药基因tetM可通过质粒接合作用转移到受体菌EC600中。作者对市售发酵食品乳酸菌进行了耐药性评估与传播风险研究,为保障发酵食品安全提供理论依据。

单菌和混合菌发酵餐厨垃圾产乳酸研究

以餐厨垃圾为原料产乳酸可显著降低乳酸的工业生产成本,并实现餐厨垃圾的高值资源化利用,但餐厨垃圾组成复杂,在乳酸发酵过程中存在底物转化率和乳酸产量低等问题。研究了植物乳杆菌(单菌)、甜酒曲(含根霉属和鼠李糖乳杆菌的混合菌)及泡菜粉(含植物乳杆菌、嗜酸乳杆菌和鼠李糖乳杆菌的混合菌)这3种接种物对餐厨垃圾发酵产乳酸的影响,结果表明:与不添加接种物的对照组相比,添加3种接种物均可提高乳酸产量,其中接种甜酒曲时乳酸发酵性能最佳;在底物负荷为20~180 g/L的范围内,乳酸产量随底物负荷的增大呈现先增大后减小的变化趋势。采用响应面法对甜酒曲接种时餐厨垃圾的乳酸发酵工艺进行了优化,得到优化工艺条件为:pH7、温度30℃、接种量18.75%、底物负荷100 g/L,在此条件下实验测得乳酸的最高产量为(82.34±2.40) g/L,乳酸转化率达82.34%。

传统发酵食品来源乳酸菌在酸奶中的应用研究

本研究以山西地区传统发酵食品来源的70株乳酸菌为研究对象,首先进行单菌株发酵特性的研究,将发酵性能优良菌株同酸奶基础发酵剂嗜热链球菌和保加利亚乳杆菌进行复合发酵,通过测定酸乳滴定酸度、pH、质构性质和感官特性,筛选可用于酸奶发酵的潜在菌株。在对70株乳酸菌进行单菌株发酵特性的研究中发现,菌株M6-2、M8-2、M10-1、M10-2在脱脂乳中培养24 h后,发酵特性较好,酸度分别可达到72.30±2.76°T、60.57±5.53°T、68.39±8.29°T、121.15±11.05°T;pH可达到5.16±0.02、5.19±0.02、4.78±0.01、4.03±0.06,且凝乳状态较好。在进一步通过与基础发酵剂复合发酵脱脂乳中发现,四株菌分别与基础发酵剂发酵酸奶中,M10-2的感官评价得分较高,总分为85.45。滴定酸度和pH分别为90.12±10.16°T、4.37±0.01。硬度、凝胶强度、弹性、内聚性、胶着性等质构特性分别为21.77±2.35 gf、38.62±3.86 gf、0.63±0.05、0.36±0.01、7.88±0.32 gf。经综合评定,菌株M10-2较适用于酸乳发酵剂的开发。

具有抑菌活性乳酸菌的分离、鉴定及其生长特性研究

以枯草芽孢杆菌(Bacillus subtilis)、大肠杆菌(Escherichia coli)、普通变形杆菌(Proteus vulgaris)为指示菌,采用传统培养分离法结合牛津杯法从传统发酵食品中筛选具有抑菌活性的乳酸菌,对其发酵上清液的稳定性及生长特性进行研究,并通过分子生物学技术对其进行鉴定。结果表明,筛选得到4株具有良好抑菌活性的乳酸菌菌株,编号为Y1、Y4、Y14、Y15。4株菌株的发酵上清液均能抑制3种指示菌的生长,其中,菌株Y1抑菌活性较好,对3种指示菌的抑菌圈直径均>13 mm,其发酵上清液在60℃、100℃处理后的抑菌活力>69%;菌株Y1、Y14、Y15发酵上清液经酸碱处理后再调回后抑菌活力仍>67%。4株菌株的生长曲线与产酸特性和抑菌活性存在生长偶联相关性,进入稳定期后,抑菌圈直径趋于稳定,可在发酵12~18 h时终止发酵。4株菌株均在pH 5.0~7.0时生长良好,最适生长pH均为6.0,其中菌株Y15耐酸性及耐渗透性较好,菌株Y1耐碱性较好。经鉴定,菌株Y1和Y4均为发酵乳杆菌(Lactobacillus fermentum),菌株Y14和Y15均为植物乳杆菌(Lactiplantibacillus plantarum)。