乳品丙酸杆菌及其产生的细菌素研究概况

乳品丙酸杆菌是应用于食品工业中的有益菌,能产生包括细菌素在内的多种有益代谢产物.近十几年来国际上报道了多种由乳品丙酸杆菌产生的细菌素,具有热稳定性且有宽作用pH值范围,能抑制多种G-菌和一些霉菌和酵母菌,有望作为新的生物防腐剂被开发应用于食品防腐保鲜.就国内外近十几年来对乳品丙酸杆菌的分类鉴定、特性和安全性以及其产细菌素的种类、理化性质、抑菌效果等方面的最新研究和应用现状进行综述和讨论.     

丙酸杆菌素高产菌株的诱变选育

丙酸杆菌素是乳品丙酸杆菌代谢合成的一种重要的多肽或蛋白质,能抑制革兰氏阴性菌、部分革兰氏阳性菌、霉菌和酵母菌的生长。以丙酸杆菌Propionibacterium feudenreichiiCS01为出发菌株,采用紫外(UV)和亚硝基胍(NTG)复合诱变的方法,获得高产突变株N11和N42,其抑菌活性达到28.63、28.83AU/mL,分别比原始出发菌株(21.14AU/mL)提高了35.4%和36.4%。     

丙酸杆菌素高产菌株的诱变选育

丙酸杆菌素是乳品丙酸杆菌代谢合成的一种重要的多肽或蛋白质,能抑制革兰氏阴性菌、部分革兰氏阳性菌、霉菌和酵母菌的生长。以丙酸杆菌Propionibacterium feudenreichiiCS01为出发菌株,采用紫外(UV)和亚硝基胍(NTG)复合诱变的方法,获得高产突变株N11和N42,其抑菌活性达到28.63、28.83AU/mL,分别比原始出发菌株(21.14AU/mL)提高了35.4%和36.4%。      

不同初始pH对丙酸杆菌细菌素发酵的影响

薛氏丙酸杆菌在不同初始pH下摇瓶厌氧发酵,测定发酵液的pH、生物量、还原糖、氨基氮及抑菌活性,探求不同初始pH对丙酸杆菌细菌素发酵的影响。将初始pH为6.0,6.5,7.0,7.5,8.0的培养基分批进行发酵,结果显示:丙酸杆菌在初始pH为6.5时,发酵第2d的生物量为8.4mg/mL,与其他初始pH的差异极显著(P<0.01);以酵母菌和恶臭假单胞菌为指示菌,发酵产物细菌素的抑菌活性在第7d达到最大,初始pH6.5的抑菌活性分别为19.203AU/mL和24.827AU/mL,与其他初始pH的差异均极显著(P<0.01),说明不同初始pH对丙酸杆菌细菌素发酵有很大的影响,其最适初始pH为6.5。     

pH对费氏丙酸杆菌细菌素抑菌性的影响

以实验室保存的一株费氏丙酸杆菌CS1420(Propionibacterium freudenreichii CS1420)为试验菌株。首先考察了不同初始pH下对其发酵产细菌素的影响。结果表明:以大肠杆菌ATCC25922为指示菌,当培养基初始pH为6.0时,细菌素抑菌效果最好;以Saccharomyces cerevisiae 2-10515为指示菌,当培养基初始pH为5.5时,细菌素抑菌效果最好。然后用丙酸调节细菌素粗提物的pH进行抑菌试验,结果表明,pH对粗提得到的细菌素抑菌性影响很大,当用丙酸将细菌素溶液的pH调至5.5时,细菌素的抑菌活性有显著提高。     

费氏丙酸杆菌发酵生产V_B_(12)

VB12广泛应用于医药业和食品工业,费氏丙酸杆菌是其主要的工业生产菌种。费氏丙酸杆菌发酵过程中会产生大量丙酸和乙酸,有机酸的积累会抑制菌体生长,延长发酵周期。通过改进发酵工艺来解除有机酸抑制,提高发酵产量是费氏丙酸杆菌发酵工艺的主要研究内容。VB12是费氏丙酸杆菌胞内产物,提取工艺对生产总收率具有重要作用。耦合发酵工艺改造和膜分离技术目前是费氏丙酸杆菌发酵VB12的研究热点。     

丙酸杆菌素的发酵及其分离纯化的初步探究

本文以薛氏丙酸杆菌(Propionibacterium shermanii)发酵液为原料,以抑菌活性为指标,利用分离纯化技术提取发酵液中小分子丙酸杆菌素。丙酸杆菌素初步分离纯化确定的最佳脱盐条件为:上样量5 m L,流速0.5 m L/min,收集方式为手动收集,电导率达到1.5 ms/cm时停止收集;Superdex peptide最佳凝胶过滤条件为:上样量500μL,流速0.5 m L/min,深孔板固定体积收集,每孔收集体积200μL。最终得到一种分子量为698.9556 u的丙酸杆菌素,其单位抑菌活性为初始的6.8倍,抑菌活性得率为10.9%。酶解实验表明纯化后的丙酸杆菌素仍保留抑菌活性,且对胃蛋白酶敏感。      

丙酸杆菌的研究进展及其在食品发酵工业中的应用

主要介绍了丙酸杆菌的特性、分类以及其在食品发酵工业中的应用。其应用非常广，主要应用于丙酸、维生素和杆菌素的生产，并简单介绍了它在其他方面的应用.     

分批补料高密度发酵生产丙酸杆菌素及其结构分析

采用分批补料高密度发酵的方法提高丙酸杆菌素的抑菌活性。从发酵96 h开始,每隔24 h补加2.5 g/L复合碳源（乳酸钠-葡萄糖质量比3∶1）和复合氮源（酵母溶液-玉米酒糟清液体积比1∶30）各100 mL,连续补加5 次后,丙酸杆菌素的抑菌活性从17.6 AU/mL提高到31.2 AU/mL。本研究创新性地将玉米酒糟清液作为发酵氮源代替部分酵母溶液,大大降低了丙酸杆菌素的生产成本。另外,通过红外光谱及蛋白酶敏感实验发现丙酸杆菌素是一种具有抑菌活性的蛋白类物质。本研究结果为丙酸杆菌素的工业化生产及其应用提供一定理论支持。     

臭豆腐发酵过程中丙酸形成的机制

为探究臭豆腐发酵过程中丙酸产生的原因及机制，采用宏基因组学对卤水和臭豆腐中微生物组成进行分析鉴定。与丙酸含量极低的“对照卤水”相比，1号臭豆腐卤水中产丙酸的丙酸杆菌属种类和丰度整体上升，其中丙酸杆菌科细菌NML＿160184的丰度上升7.6倍，产酸丙酸杆菌的丰度上升4.7倍，丙酸杆菌＿细菌的丰度上升3.8倍。与2号臭豆腐相比，1号成品豆腐中产丙酸的丙酸杆菌属种类和丰度也显著增加，丙酸杆菌科细菌P6A17的丰度上升59.4倍，未分类丙酸杆菌科的丰度上升54.9倍，丙酸杆菌＿细菌的丰度上升47倍，假丙酸杆菌＿massiliense的丰度上升29.7倍。采用非靶向代谢组学分析卤水中微生物代谢产物和功能，结果发现不同卤水的微生物组成的代谢活动有显著差异，臭豆腐中丙酸水平的差异极有可能是受卤水中微生物的种类和代谢活动的影响。结论：臭豆腐中检出丙酸是因发酵过程中微生物自然产生而非人为添加，不同来源的卤水产丙酸菌的种类和丰度也不同，最后产品的丙酸含量也会呈现显著差异。     

Functionality of enterococci in dairy products

Enterococci have important implications in the dairy industry. They occur as nonstarter lactic acid bacteria (NSLAB) in a variety of cheeses, especially artisan cheeses produced in southern Europe from raw or pasteurised milk, and in natural milk or whey starter cultures. They play an acknowledged role in the development of sensory characteristics during ripening of many cheeses and have been also used as components of cheese starter cultures. The positive influence of enterococci on cheese seems due to specific biochemical traits such as lipolytic activity, citrate utilisation, and production of aromatic volatile compounds. Some enterococci of dairy origin have also been reported to produce bacteriocins (enterocins) inhibitory against food spoilage or pathogenic bacteria, such as Listeria monocytogenes, Staphylococcus aureus, Vibrio cholerae, Clostridium spp., and Bacillus spp. The technological application of enterocins, shown to be produced during cheese manufacture, led to propose enterococci as adjunct starter or protective cultures in cheeses. There is evidence that enterococci, either added as adjunct starters or present as nonstarter NSLAB, could find potential application in the processing of some fermented dairy products. Literature suggest that the complex biochemical and ecological phenomena explaining the technological functionality of the enterococci in dairy products, are still to be fully understood. Clearly, the clinical research on enterococci underlines also that the safety of dairy products containing enterococci is an issue that the industry must carefully address before proceeding to their application.     

乳酸菌素的研究现状和发展趋势

乳酸菌素是由乳酸菌产生的一种具有活性的多肽或蛋白质物质，大部分细菌素对近缘关系的细菌有抑制作用，少数细菌素抑菌谱很广。主要可分为热稳定的小分子肽，热敏感的大分子蛋白和羊毛硫抗生素。乳酸菌素是一种纯乳酸菌产生的制剂，是将脱脂乳经杀菌、真空浓缩．再经乳酸菌发酵后干燥而制成的乳酸菌体及其代谢产物混价粉状物，可作医药用或食品添加剂，属疗效型乳制品。本文对乳酸菌素的分类、抑菌机理及在食品和医药方面的应用作了全面系统的综述，并指出了今后的研究方向和应用前景。     

Probiotics in the dairy industry—Advances and opportunities

The past two decades have witnessed a global surge in the application of probiotics as functional ingredients in food, animal feed, and pharmaceutical products. Among food industries, the dairy industry is the largest sector where probiotics are employed in a number of dairy products including sour/fermented milk, yogurt, cheese, butter/cream, ice cream, and infant formula. These probiotics are either used as starter culture alone or in combination with traditional starters, or incorporated into dairy products following fermentation, where their presence imparts many functional characteristics to the product (for instance, improved aroma, taste, and textural characteristics), in addition to conferring many health-promoting properties. However, there are still many challenges related to the stability and functionality of probiotics in dairy products. This review highlights the advances, opportunities, and challenges of application of probiotics in dairy industries. Benefits imparted by probiotics to dairy products including their role in physicochemical characteristics and nutritional properties (clinical and functional perspective) are also discussed. We transcend the traditional concept of the application of probiotics in dairy products and discuss paraprobiotics and postbiotics as a newly emerged concept in the field of probiotics in a particular relation to the dairy industry. Some potential applications of paraprobiotics and postbiotics in dairy products as functional ingredients for the development of functional dairy products with health-promoting properties are briefly elucidated.     

牛生长激素在乳业中的应用及其安全性

概述了牛生长激素在乳业中的应用及其作用效果，并对牛生长激素在乳业中的发展前景及其安全性问题进行了讨论。结果表明，牛生长激素可以有效的提高牛的产奶量和饲料利用率，并可以有效的降低乳业生产成本；不论是天然牛生长激素还是采用基因重组技术生产的牛生长激素都不会对人和动物的健康造成危害。但对于其安全性还有待于进一步的研究，     

Exploring the impact of sexed semen on the structure of the dairy industry

Widespread commercial application of sexed semen is expected within the next decade because of continued improvements in fertility of sexed semen and sorting capacity. The objective of this study was to explore the potential impact of widespread application of sexed semen on the structure of the dairy industry in the United States. Historically, female offspring from all heifers and cows were needed to produce enough dairy replacement heifers to replace culled cows. The use of sexed semen allows for a decoupling of breeding decisions necessary to obtain an adequate supply of dairy replacement heifers from those needed to achieve pregnancies needed to start new lactations. Application of sexed semen allows dairy producers to select among their herds’ potential dams and produce dairy replacement heifers from only the genetically superior animals. The rate of genetic progress is expected to increase, but not more than 15% of the rate of gain accomplished through sire selection achieved through conventional (nonsexed) artificial insemination breeding. The supply of dairy replacement heifers is expected to grow to meet and temporarily exceed current demand, resulting in reduced prices for dairy replacement heifers. Consequently, herd turnover rates are expected to increase slightly, and herd expansions may accelerate. The rate of consolidation of dairy farms is expected to increase. Widespread application of sexed semen may temporarily increase the supply of milk, which would result in lower milk prices. The cost of milk production will be reduced as well. Many breeding options exist for the genetically poorer cows in the herd. The optimal breeding mix depends on the value of the various kinds of calves that could be produced. More crossbred calves for beef production may be produced; however, a market for these crossbred calves is not well established. Increased specialization is expected with more dairy producers deciding not to raise their own heifers but to purchase replacements. Other dairy farms might specialize in producing genetically superior dairy replacement heifers for sale. Depending on the value of calves not raised for replacements, artificial insemination organizations might market beef conventional semen or beef male sexed semen to dairy farms. The use of sexed semen should lower the cost of progeny-testing programs and embryo transfer and enhance the value of genetic markers. Eventually, the economic benefits from the use of sexed semen will be passed on to consumers.     

Innovation in milk powder technology

Global trade in preserved milks is on the increase as new markets open up in regions of the world that have not been traditionally associated with milk consumption. Equally, a rise in world milk production is forecasted to continue, and the indications are that significant quantities of the extra milk produced will be converted to commodity products such as butter and powders. Consequently, on-going investment in new spray drying capability is likely to track geographical shifts in milk production. Successful application of advanced process control to the operation of large scale drying plant is both a priority and a challenge.
  Meanwhile, opportunities for the exploitation of milk as a source of functional ingredients are being availed of by the dairy industry as it continues to achieve added value and unique key selling points. Recent research on the role of spray drying, along with other processes in the development of dairy ingredients for applications in chocolate and the preparation of microencapsulated powders, is reviewed.     

Innovative Uses of Milk Protein Concentrates in Product Development

Milk protein concentrates (MPCs) are complete dairy proteins (containing both caseins and whey proteins) that are available in protein concentrations ranging from 42% to 85%. As the protein content of MPCs increases, the lactose levels decrease. MPCs are produced by ultrafiltration or by blending different dairy ingredients. Although ultrafiltration is the preferred method for producing MPCs, they also can be produced by precipitating the proteins out of milk or by dry‐blending the milk proteins with other milk components. MPCs are used for their nutritional and functional properties. For example, MPC is high in protein content and averages approximately 365 kcal/100 g. Higher‐protein MPCs provide protein enhancement and a clean dairy flavor without adding significant amounts of lactose to food and beverage formulations. MPCs also contribute valuable minerals, such as calcium, magnesium, and phosphorus, to formulations, which may reduce the need for additional sources of these minerals. MPCs are multifunctional ingredients and provide benefits, such as water binding, gelling, foaming, emulsification, and heat stability. This article will review the development of MPCs and milk protein isolates including their composition, production, development, functional benefits, and ongoing research. The nutritional and functional attributes of MPCs are discussed in some detail in relation to their application as ingredients in major food categories.     

Some aspects of the periurban dairy system in Cameroon

A survey to establish baseline data for future intervention in milk and dairy production in the peri-urban areas of Garoua, Maroua and Bamenda was carried out. Dairy products are still produced in a traditional way in areas around Maroua and Garoua with milk from native zebu cattle (Red and White Fulani breeds). The important dairy products are pendidam and kindirmu, both of which are fermented milks. Naturally sour milk was found occasionally. Around Bamenda, milk is produced by herds comprising pure Holsteins, Jerseys and their crosses with local zebu cows; cross-breeding is being intensified to increase rapidly the size of the dairy herds. Appreciable volumes of milk are produced daily, so allowing the industrial processing of fresh milk into pasteurized milk, yogurt and cheese. The potential for expansion of the dairy industry, and the possible constraints, were identified and solutions proposed.     

Digesters and demographics: identifying support for anaerobic digesters on dairy farms

The dairy industry in the United States is amidst a long-running trend toward fewer, larger dairy farms. This development has created a backlash in some communities over concerns such as odor, waste management, and environmental degradation. Separately, anaerobic digestion has advanced as a waste management technology that potentially offers solutions to some of these issues, providing odor control and a combustible biogas among other things. These digesters require significant capital investments. Voluntary consumer premiums for the renewable energy produced have been used in some instances as a means to move adoption of such systems toward financial feasibility. This project employed a survey to measure Ohio consumers’ willingness to pay a premium for renewable energy produced by anaerobic digesters on dairy farms. Cluster analysis was used to segment consumers by willingness to pay, age, education, income, self-identified political inclination, and a composite variable that served as a proxy for respondents’ environmental stewardship. Four distinctive groups emerged from the data. Older, less educated respondents were found to have the least amount of support for digesters on dairy farms, whereas politically liberal, environmentally proactive respondents demonstrated the strongest support. Well-educated, affluent respondents and young respondents fell between these 2 groups. Most large dairy farms are generally met with fairly negative responses from their local communities; in contrast, this research finds some popular support for anaerobic digestion technology. Going forward, establishing a positive link between support for anaerobic digesters and for their use on large dairies could open up a new route for less-contested large dairy farm developments. Evaluation of community demographics could become an important part of finding an optimal location for a large dairy farm.     

ADSA Foundation Scholar Award: Possibilities and challenges of exopolysaccharide-producing lactic cultures in dairy foods

Exopolysaccharides (EPS) from lactic acid bacteria are a diverse group of polysaccharides exhibiting various functional properties. Two forms of EPS are produced by lactic acid bacteria: capsular and unattached. Capsular EPS does not cause ropiness nor does production of unattached EPS ensure ropiness. The functions of EPS in dairy products are not completely understood. This is for 2 main reasons: the major variations among exopolysaccharides even from the same group of micro-organisms, which makes it difficult to apply information from one EPS to others, and the lack of availability of techniques with the ability to observe the microstructure and distribution of the highly hydrated EPS in fermented dairy products. The introduction of relatively new microscopic techniques such as confocal scanning laser microscopy and cryo-scanning electron microscopy made it possible to directly observe the distribution of fully hydrated EPS in dairy products. Recently, EPS produced by nonropy strains have drawn the attention of the dairy industry. This is because of the ability of some nonropy strains to produce large capsular and unattached EPS that would improve the texture of dairy products without causing the undesirable slippery mouthfeel produced by the ropy strains. Factors affecting functions of EPS are their molecular characteristics and ability to interact with milk proteins. Studying the interaction between EPS and milk proteins is complex because EPS are gradually produced during fermentation, unlike polysaccharides added directly to milk to stabilize the fermented product. The concentration and possibly molecular characteristics of EPS and protein characteristics such as charge and hydrophobicity change during fermentation. Consequently, the interaction of EPS with proteins might also change during fermentation. Exopolysaccharides provide functions that benefit reduced-fat cheeses. They bind water and increase the moisture in the nonfat portion, interfere with protein-protein interactions and reduce the rigidity of the protein network, and increase viscosity of the serum phase. This review discusses the production of capsular EPS and their role in structure formation in fermented milk, the mechanism of ropiness formation, and applications of EPS-producing cultures in reduced-fat cheeses.