益生菌发酵乳低温酸性双重胁迫致益生菌损伤 机制的研究进展

益生菌是一类对宿主有益的活性微生物,是定植于人体肠道、生殖系统内,能产生确切健康功效从而改善宿主微生态平衡、发挥有益作用的活性有益微生物的总称。近年,有关益生菌发酵乳中低温酸性双胁迫致益生菌的损伤,发酵乳中益生菌活性的保护,以及组学技术推动下的菌株损伤相关代谢研究取得了一定进展。本文综述了益生菌低温酸性双胁迫下损伤应激和保护机制、菌株特性对发酵乳风味和质量的影响及益生菌发酵乳冷藏过程低温酸性双重胁迫下菌体活性的保护策略,为研究影响益生菌发酵乳中益生菌存活能力、菌体细胞膜特性及代谢酶活性的因素,明确益生菌发酵乳基质中益生菌低温酸性双胁迫损伤的分子机制,建立益生菌发酵乳加工和贮藏过程中益生菌的保护策略提供参考,也为未来改善益生菌发酵乳的功效和品质提供了科学依据。     

Probiotic potential and biochemical and technological properties of Lactococcus lactis ssp. lactis strains isolated from raw milk and kefir grains

Lactococcus lactis ssp. lactis is one of the most important starter bacteria used in dairy technology and it is of great economic importance because of its use in the production of dairy products, including cheese, butter, cream, and fermented milks. Numerous studies have evaluated the biochemical and probiotic properties of lactococci; however, limited studies on the probiotic characteristics of lactococci were conducted using strains originating from raw milk and dairy products. Characterizing the probiotic properties of strains isolated from raw milk and fermented milk products is important in terms of selecting starter culture strains for the production of functional dairy products. In this study, biochemical properties (including antibiotic sensitivity, lipolytic activity, amino acid decarboxylation, antioxidant activity) and probiotic properties (including antimicrobial activity, growth in the presence of bile salts, bile salts deconjugation, and hydrophobicity) of 14 Lactococcus lactis strains isolated from raw milk and kefir grains were investigated. Strains originating from kefir grains had better characteristics in terms of antimicrobial activity and bile salt deconjugation, whereas strains from raw milk had better hydrophobicity and antioxidant activity characteristics. None of the strains were able to grow in the presence of bile salt and did not show amino acid decarboxylation or lipolytic activities. Biochemical and probiotic properties of L. lactis strains varied depending on the strain and some of these strains could be used as functional cultures depending on their properties. However, these strains did not possess all of the properties required to meet the definition of a probiotic.     

乳制品中益生菌存活力的影响因素与提高方法

提高乳制品中益生菌的存活力是目前益生菌乳制品研制与开发的技术关键。本文根据益生菌的生理特性并结合国内外益生菌乳制品研究开发进展,探讨了菌种(株)、菌种(株)之间的相互关系、营养基质、生产工艺、氧及氧化还原电位等因素对乳制品中益生菌存活力的影响,提出了相应的改进方法与技术措施,以期为进一步发展益生菌乳制品提供科学依据。     

Effect of buckwheat flour and oat bran on growth and cell viability of the probiotic strains Lactobacillus rhamnosus IMC 501®, Lactobacillus paracasei IMC 502® and their combination SYNBIO®, in synbiotic fermented milk

Fermented foods have a great significance since they provide and preserve large quantities of nutritious foods in a wide diversity of flavors, aromas and texture, which enrich the human diet. Originally fermented milks were developed as a means of preserving nutrients and are the most representatives of the category. The first aim of this study was to screen the effect of buckwheat flour and oat bran as prebiotics on the production of probiotic fiber-enriched fermented milks, by investigating the kinetics of acidification of buckwheat flour- and oat bran-supplemented milk fermented by Lactobacillus rhamnosus IMC 501®, Lactobacillus paracasei IMC 502® and their 1:1 combination named SYNBIO®. The probiotic strains viability, pH and sensory characteristics of the fermented fiber-enriched milk products, stored at 4 °C for 28 days were also monitored. The results showed that supplementation of whole milk with the tested probiotic strains and the two vegetable substrates results in a significant faster lowering of the pH. Also, the stability of L. rhamnosus IMC 501®, L. paracasei IMC 502® and SYNBIO® during storage at 4 °C for 28 days in buckwheat flour- and oat bran-supplemented samples was remarkably enhanced. The second aim of the study was to develop a new synbiotic product using the best combination of probiotics and prebiotics by promoting better growth and survival and be acceptable to the consumers with high concentration of probiotic strain. This new product was used to conduct a human feeding trial to validate the fermented milk as a carrier for transporting bacterial cells into the human gastrointestinal tract. The probiotic strains were recovered from fecal samples in 40 out of 40 volunteers fed for 4 weeks one portion per day of synbiotic fermented milk carrying about 10⁹ viable cells.     

Evaluation of the effect of supplementing fermented milk with quinoa flour on probiotic activity

In this work, we investigated the effect of supplementing fermented milk with quinoa flour as an option to increase probiotic activity during fermented milk production and storage. Fermented milk products were produced with increasing concentrations of quinoa flour (0, 1, 2, or 3 g/100 g) and submitted to the following analyses at 1, 14, and 28 d of refrigerated storage: postacidification, bacterial viability, resistance of probiotics to simulated gastrointestinal (GI) conditions, and adhesion of probiotics to Caco-2 cells in vitro. The kinetics of acidification were measured during the fermentation process. The time to reach maximum acidification rate, time to reach pH 5.0, and time to reach pH 4.6 (end of fermentation) were similar for all treatments. Adding quinoa flour had no effect on fermentation time; however, it did contribute to postacidification of the fermented milk during storage. Quinoa flour did not affect counts of Bifidobacterium animalis ssp. lactis BB-12 or Lactobacillus acidophilus La-5 during storage, it did not protect the probiotic strains during simulated GI transit, and it did not have a positive effect on the adhesion of probiotic bacteria to Caco-2 cells in vitro. Additionally, the adhesion of strains to Caco-2 cells decreased during refrigerated storage of fermented milk. Although the addition of up to 3% quinoa flour had a neutral effect on probiotic activity, its incorporation to fermented milk can be recommended because it is an ingredient with high nutritive value, which may increase the appeal of the product to consumers.     

In vitro investigation of anticancer,antihypertensive, antidiabetic,and antioxidant activities of camel milk fermented with camel milk probiotic: A comparative study with fermented bovine milk

This study aimed to investigate in vitro anticancer activity by antiproliferative activity, antihypertensive activity by angiotensin-converting enzyme inhibition, antidiabetic activity by α-amylase and α-glucosidase inhibitions, and antioxidant activities of camel milk fermented with camel milk probiotic compared with fermented bovine milk. The camel milk probiotic strain Lactococcus lactis KX881782 (Lc.K782) and control Lactobacillus acidophilus DSM9126 (La.DSM) were used to prepare fermented camel and bovine milks separately. The proteolytic activities of water-soluble extract (WSE) in all fermented camel milk were higher than those in fermented bovine milk. The α-glucosidase inhibitions in both milk types fermented by Lc.K782 ranged from 30 to 40%. Camel milk fermented by Lc.K782 had the highest antioxidant activity by 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulphonic acid). The highest angiotensin-converting enzyme inhibition of WSE in camel milk fermented by Lc.K782 was >80%. The proliferations of Caco-2, MCF-7, and HELA cells were more inhibited when treated with WSE of fermented camel milk extracts.     

Growth of autobioluminescent Campylobacter jejuni in response to various environmental conditions

An autobioluminescent Campylobacter jejuni organism generated from the fusion of luxCDABE genes from Xenorhabdus luminescens to the flaA promoter of C. jejuni was used in conjunction with gel-stabilized gradient plates to map the responses of this organism to three environmental factors (pH, NaCl concentration, and temperature) and various concentrations of L-fucose, D-fucose, and sodium desoxycholate. The minimum, optimum, and maximum temperatures for the growth of autobioluminescent C. jejuni ATCC 35921 in solid media were found to be 30, 40, and 45 degrees C, respectively. At its optimum growth temperature, C. jejuni ATCC 35921 was able to grow well at pHs of 5.5 to 8.0 and in the presence of up to 1.70 to 1.75% NaCl. At its minimum growth temperature, however, C. jejuni ATCC 35921 could grow only at pHs of 6.5 to 8.0 and in the presence of up to 0.5% NaCl. L-Fucose, D-fucose, and sodium desoxycholate were shown to inhibit the growth of C. jejuni. Autobioluminescent C. jejuni was also used to determine whether the flaA promoter responds to both environmental conditions and chemical stimulants. While sodium desoxycholate was found to down-regulate C. jejuni flaA promoter activity, L-fucose was found to up-regulate its activity. Sodium chloride, pH, and D-fucose were all shown to exert no significant effects on promoter activity. Bacterial bioluminescence in combination with two-dimensional gradient gels is a powerful tool for studying the behavior of bacteria exposed to various environments.     

Effect of Different Aloe Fractions on the Growth of Lactic Acid Bacteria

Several foods on the market, such as yogurt and fermented milk, include mixtures of prebiotics and probiotic microorganisms effective in promoting the proliferation and equilibrium of intestinal bacteria, thus improving gut health. Particularly, researchers and the public have shown increasing interest in the combination of probiotics with natural substances that promote health or that can act as substrates to promote bacterial growth. The aim of this study is to evaluate the effects of different extracts of Aloe barbadensis and Aloe arborescens in fermented milk, taking into account both the prebiotic effect of aloe polysaccharides and the antimicrobial activity of several secondary metabolites. The results demonstrate a beneficial effect of 5% aloe inner gel on Lactobacillus growth and confirm the antimicrobial activity of the phenolic compounds peculiar of green rind extracts.     

Effect of milk base and starter culture on acidification,texture, and probiotic cell counts in fermented milk processing

In the present work, the compared effect of milk base and starter culture on acidification, texture, growth, and stability of probiotic bacteria in fermented milk processing, was studied. Two strains of probiotic bacteria were used, Lactobacillus acidophilus LA5 and L. rhamnosus LR35, with two starter cultures. One starter culture consisted only of Streptococcus thermophilus ST7 (single starter culture); the other was a yogurt mixed culture with S. thermophilus ST7 and L. bulgaricus LB12 (mixed starter culture). For the milk base preparation, four commercial dairy ingredients were tested (two milk protein concentrates and two casein hydrolysates). The resulting fermented milks were compared to those obtained with control milk (without enrichment) and milk added with skim milk powder. The performance of the two probiotic strains were opposite. L. acidophilus LA5 grew well on milk but showed a poor stability during storage. L. rhamnosus LR35 grew weakly on milk but was remarkably stable during storage. With the strains tested in this study, the use of the single starter culture and the addition of casein hydrolysate gave the best probiotic cell counts. The fermentation time was of about 11 h, and the probiotic level after five weeks of storage was greater than 106 cfu/ml for L. acidophilus LA5 and 10(7) cfu/ml for L. rhamnosus LR35. However, an optimization of the level of casein hydrolysate added to milk base has to be done, in order to improve texture and flavor when using this dairy ingredient.     

Review Article: Technological Aspects of Prebiotics in Probiotic Fermented Milks

Prebiotics are food components that exert beneficial effects on health of the host, associated with modulation of the intestinal flora via stimulating the growth and/or activity of the probiotics. One of the recommended ways to maintain high viable numbers of probiotic bacteria in the intestine as well as in the probiotic fermented milk products until the time of consumption is via the use of prebiotics. These compounds can also affect sensory profile, physicochemical and rheological characteristics, and economic properties of probiotic fermented milk products. In this article, technological aspects of prebiotics (viability of probiotics in the product as well as the physicochemical, rheological, sensory, and economic characteristics of product) in probiotic fermented milks are reviewed.     

Influence of cofermentation by amylolytic Lactobacillus strains and probiotic bacteria on the fermentation process,viscosity and microstructure of gruels made of rice,soy milk and passion fruit fiber

Gruels tailored to school-age children and made of soy milk and rice flour with or without total dietary fiber from passion fruit by-product were fermented by amylolytic lactic acid bacteria strains (Lactobacillus fermentum Ogi E1 and Lactobacillus plantarum A6), by commercial probiotic bacteria strains (Lactobacillus acidophilus L10, Lactobacillus casei L26 and Bifidobacterium animalis subsp. lactis B94) and by co-cultures made of one amylolytic and one probiotic strain. The influence of ingredient composition and bacterial cultures on kinetics of acidification, α-amylase activity of the bacteria, apparent viscosity and microstructure of the fermented products was investigated. During fermentation of the gruels, α-amylase activity was determined through the Ceralpha method and apparent viscosity, flux behavior and thixotropy were determined in a rotational viscometer. Rheological data were fitted to Power Law model. The combination of amylolytic and probiotic bacteria strains reduced the fermentation time of the gruels as well as increased the α-amylase activity. The addition of passion fruit fiber exerted less influence on the apparent viscosity of the fermented products than the composition of the bacterial cultures. Scanning electron microscopy provided evidence of exopolysaccharide production by amylolytic bacteria strains in the food matrices tested. The co-cultures made of amylolytic and probiotic bacteria strains are suitable to reduce the fermentation time of a soy milk/rice matrix and to obtain a final product with pH and viscosity similar to yoghurt.     

Probiotics in the new millennium

Beneficial effects on human health by specific probiotic microorganisms such as prevention of gastrointestinal tract infections, immune stimulation, and balancing of the intestinal microflora have been established in numerous clinical trials. The successful probiotic strains, which are mainly members of Lactobacillus and more recently Bifidobacterium naturally found in the human intestinal tract, have been traditionally incorporated into fermented milk products but have excellent potential for further inclusion in functional foods and health-related products. While the health claims are generally accepted by both scientists and consumers, often the molecular mechanisms underlying the probiotic properties remain controversial. Further progress concerning the molecular basis of probiotic traits will give vital reinforcement to the probiotic concept and is a prerequisite for rational development into further applications. In this review, current research on the genetics of properties of the intestinal lactobacilli that may contribute to the activity and effectiveness of probiotics is described. The potential of molecular biology for future probiotic applications is addressed and a probiotic strain developed by modern biotechnology with advantages for specific consumers is presented.     

发酵酸菜来源乳酸菌的益生特性及其在发酵乳中的应用

通过pH值、胆盐耐受性实验从发酵酸菜中筛选性能优良的益生乳酸菌株,经16S rRNA序列分析鉴定得4 株植物乳杆菌A44、B51、B54、C53和2 株戊糖乳杆菌A16、B72。经疏水、黏附、自凝聚和溶血能力实验评价6 株乳酸菌的益生特性,其中植物乳杆菌A44对氯仿和二甲苯的疏水性均大于80%,对Caco-2细胞的黏附率为13.57%,放置5 h的自凝聚率超过60%,与其他菌株相比具有更好的益生特性且无溶血活性。因此选用植物乳杆菌A44进一步研究其在发酵乳中的功能特性,结果表明：植物乳杆菌A44作为辅助发酵剂添加后对4 ℃贮藏7 d期间发酵乳pH值、滴定酸度和持水性均无显著影响（P＞0.05）,但是可以显著提高发酵乳的活菌数和黏度（P＜0.05）,活菌数达到8.45（lg（CFU/mL））。本研究筛选得到的植物乳杆菌A44是一株性能优良的益生乳酸菌,具有作为发酵乳益生菌辅助发酵剂的潜在应用前景。     

Influence of addition of raffinose family oligosaccharides on probiotic survival in fermented milk during refrigerated storage

The influence of the addition of raffinose family oligosaccharides (RFOs) extracted from lupin seeds on the survival of Bifidobacterium lactis Bb-12 and Lactobacillus acidophilus La-5 in fermented milk during 21 days of storage in refrigerated conditions was studied. For this purpose, viability and metabolic activity (expressed as pH, lactic and acetic acid production and utilization of soluble carbohydrates) of probiotic bacteria were determined. Retention of viability of B. lactis Bb-12 and L. acidophilus La-5 was greater in fermented milk with RFOs. The pH of probiotic fermented milk at 21 days of storage was lower (4.27) compared with probiotic fermented milk with RFOs (4.37). The highest levels of lactic and acetic acid were produced in probiotic fermented milk without RFOs compared with probiotic fermented milk with RFOs during storage at 4 °C. Soluble carbohydrates were utilised in fermented milk with and without RFOs, respectively, for maintaining B. lactis Bb-12 and L. acidophilus populations during refrigerated storage. In conclusion, all these experiments provide convincing evidence that RFOs have beneficial effects on the survival of these probiotic cultures in dairy products. As a result, such stored dairy products containing both probiotics and prebiotics have synergistic actions in the promotion of health.     

The effects of probiotics in lactose intolerance: A systematic review

Over 60 percent of the human population has a reduced ability to digest lactose due to low levels of lactase enzyme activity. Probiotics are live bacteria or yeast that supplements the gastrointestinal flora. Studies have shown that probiotics exhibit various health beneficial properties such as improvement of intestinal health, enhancement of the immune responses, and reduction of serum cholesterol. Accumulating evidence has shown that probiotic bacteria in fermented and unfermented milk products can be used to alleviate the clinical symptoms of lactose intolerance (LI). In this systematic review, the effectiveness of probiotics in the treatment of LI was evaluated using 15 randomized double-blind studies. Eight probiotic strains with the greatest number of proven benefits were studied. Results showed varying degrees of efficacy but an overall positive relationship between probiotics and lactose intolerance.     

不同益生菌发酵乳ACEI活性比较

测定了6株德氏乳杆菌保加利亚亚种、6株嗜热链球菌、6株鼠李糖乳杆菌、4株双歧杆菌和天然发酵剂Kefir发酵产物的ACEI活性。结果显示,发酵产物的ACEI活性呈现种属和菌株差异性,发酵和贮藏条件对ACEI活性具有显著影响,菌株发酵结束后经冷藏,ACEI活性均有不同程度的下降。德氏乳杆菌保加利亚亚种Lb9菌株在发酵6h时的ACEI活性为60%,发酵产物在冷藏24h和48h后,ACEI活性分别为55.72%和49.64%。嗜热链球菌Stnh16菌株发酵6h时的ACEI活性显著高于其他嗜热链球菌菌株,为52.73%,冷藏24h和48h后,ACEI活性分别为48.82%和42.58%。鼠李糖乳杆菌在发酵18h时的ACEI活性最高,其中F菌株为83.19%,R26为72.72%,LV108菌株为69.44%,但是冷藏24h和48h后,ACEI活性LV108菌株显著高于其他菌株,ACEI活性分别为66.19%和62.91%,显示其适宜用作生产降血压益生菌发酵乳的发酵剂。双歧杆菌不同菌株中,H4在发酵24h时ACEI活性最高,为46.55%。Kefir在发酵24h时,其ACEI活性最弱,仅为15.23%。该研究为筛选降血压益生菌发酵乳的发酵剂及发酵乳生产提供了参考。     

发酵乳的最新进展

综述了发酵乳在科学、枝术和市场方面最新进展。介绍了在分子水平和菌株水平的乳酸菌和益生菌的菌种鉴定、乳酸菌和新益生菌株的安全性、乳酸菌胞外多糖、减少发酵乳生产过程中黏度降低的因素，以及乳酸菌和益生菌的功能保健作用。根据近年来消费者对酸奶的温和味道、香气和质地更高的要求，叙述了酸奶和其他发酵乳新产品开发的进展。     

Evaluation of the antihypertensive angiotensin-converting enzyme inhibitory (ACE-I) activity and other probiotic properties of lactic acid bacteria isolated from traditional Greek dairy products

The technological and probiotic potential of lactic acid bacteria isolated from artisanal Greek yoghurt and fermented milks were evaluated. Fifty-three strains were identified by rep-PCR and 16S rDNA sequencing to belong to different Lactobacillus or Enterococcus spp., as well as to Streptococcus thermophilus and Lactococcus lactis. Several strains exhibited promising technological and probiotic properties. Among them, we focused on the production of bioactive peptides with angiotensin-converting enzyme inhibitory (ACE-I) activity during milk fermentation. The majority of strains produced ACE-I peptides when grown in skimmed milk. ACE-I peptides were sometimes sequestered in the original fermented milk sample, but were released and detected following high performance liquid chromatography (HPLC) purification. Mass spectrometry analysis of major peptide peaks in HPLC fractions with ACE-I activity revealed that they derived from the N- or C-terminal of the isracidin peptide region of α_S1-casein and two internal peptide fragments, one from β-casein and one from κ-casein.     

In vitro comparison of probiotic properties of Lactobacillus casei Zhang, a potential new probiotic, with selected probiotic strains

Since 2004, our research group has isolated 240 Lactobacillus strains from Koumiss, a traditional fermented alcoholic beverage prepared from mare's milk in Inner Mongolia, Xinjiang of China and Mongolia. Among these Lactobacillus strains a novel strain with potential probiotic properties, Lactobacillus casei Zhang, was screened out and studied extensively for its probiotic properties, health-promoting effects and fermentation characteristics. In vitro tests indicated that L. casei Zhang had high tolerance to simulated gastric, intestine juices and bile salts, similar to commercial probiotic strains such as Lactobacillus acidophilus NCFM, Lactobacillus rhamnosus GG, L. casei Shirota and Bifidobacterium animalis Bb12. Higher acid-production activity and proteolytic activity was observed in the fermented milk inoculated with L. casei Zhang during the refrigerated storage than in the samples inoculated with the selected commercial probiotics. The yogurt samples fermented with L. casei Zhang exhibited similarer viable count (1.0 × 10⁹ cfu/mL) as the other samples after 28 d of refrigerated storage. The results suggested that L. casei Zhang showed good potential for application in functional foods and health-related products.