酸马奶酒中乳酸菌和酵母菌互作关系的研究

选取来自酸马奶酒中的2株乳酸菌(坚强肠球菌W1和粪肠球菌W2)和2株酵母菌(厚壁酵母属J1和娄德酵母属J2)进行互作关系的研究,采用固体平板涂布法的定性研究法和液体培养测定OD值、pH、滴定酸度的定量研究法。结果表明:2株乳酸菌发酵液都对酵母菌菌落生长有促进作用,发酵液经110℃、7min灭菌后,并不影响其促进作用;2株酵母菌发酵液对坚强肠球菌W1培养过程中的OD值、pH和滴定酸度无明显影响,而对粪肠球菌W2的生长及其产酸能力具有明显地促进作用;随着发酵液的添加量增加,促进作用更为明显。     

Enzymes involved in flavour formation by bacteria isolated from the smear population of surface-ripened cheese

Twenty-five bacterial isolates recovered from the surface population of smear-ripened cheese were assigned phenotypically as Brevibacterium spp ., Corynebacterium spp. and Aureobacterium spp. using the Biolog GP2 microplate system and database. The range and activity of hydrolytic enzymes involved in the formation of cheese flavour constituents were monitored in cell-free lysates of the isolates. Esterase activity and the presence of a range of enzymes involved in amino acid release and breakdown was confirmed in all strains examined although there were pronounced interspecies and strain differences in the level of activity detected. Peptidolytic activities present in the smear bacteria included dipeptidyl peptidase and aminopeptidases that cleaved various N-terminal amino acids including proline. Subsequent breakdown of the released aromatic and branched-chain amino acids was mediated by α-keto acid dependent aminotransferase action and several of the isolates were able to form thiols from sulphur-containing amino acid precursors. It was confirmed that the enzymic activity of the smear population could be manipulated by the use of defined starter cultures comprising selected combinations of smear isolates. The hydrolytic activities of the smear bacteria are involved in the generation of cheese flavour compounds and the enzyme profile is thus an important selection criterion for strains to be evaluated for use in defined surface smear preparations.     

酸马奶中一株乳酸菌与一株酵母菌共生关系和风味代谢产物的研究

对内蒙古锡盟地区酸马奶中分离出的一株乳酸菌和一株酵母菌进行混合培养,测定了双菌培养体系中的风味代谢产物,以单菌培养作为对照。结果表明:酵母菌水解蛋白能力要强于乳酸菌;双菌培养基中有利于产出更多的风味物质;乳酸菌和酵母菌在发酵过程中都可以利用苹果酸和酒石酸作为碳源进行生长,在柠檬酸的利用上,乳酸菌可以进行柠檬酸代谢,而酵母菌以产生柠檬酸为特点,暗示了二者间的相互作用关系;在双菌培养基中甲酸、乙酸、丙酸的产量在不同时期都高于单菌培养过程中的生成量,提示出乳酸菌和酵母菌存在某种共生关系。     

Cultures for the ripening of smear cheeses

Data on typical surface microflora of smeared semi-soft, soft and acid curd cheeses and the minimal composition of suitable surface starter cultures are reviewed. Cultures for semi-soft cheeses should contain Debaryomyces hansenii, Staphylococcus equorum, Corynebacterium casei, Microbacterium gubbeenense (or Arthrobacter nicotianae), and Brevibacterium linens. Apart from D. hansenii, soft cheese surface cultures should contain Geotrichum candidum, which is responsible for the typical appearance and aroma development. M. gubbeenense or A. nicotianae and B. linens are essential for soft cheese ripening, but C. casei is not. S. equorum, not regularly found on the surface of commercial soft cheeses, accelerated deacidification and smear development. Cultures for acid curd cheeses, produced from quarg, should contain Kluyveromyces marxianus and Candida krusei. Staphylococci seem to be essential for ripening. S. equorum can replace the non-food-grade S. saprophyticus that is always present on commercial acid curd cheeses. Suitable corynebacteria for spraying of cheeses are B. linens and C. variabile.     

Use of smear bacteria and yeasts to modify flavour and appearance of Cheddar cheese

The strains Staphylococcus saprophyticus DPC5671 and Corynebacterium casei DPC5298 were applied in combination with Debaryomyces hansenii DPC6258 to the surface of young Cheddar cheese curd to obtain two different smear-ripened cheeses. A surface microbiota developed over the incubation period, comprising of both yeast and bacteria; pulsed field gel electrophoresis confirmed that the inoculated strains of S. saprophyticus DPC5671 or C. casei DPC5298 were the dominant bacterial strains on the surface of the cheese at the end of the ripening period. The smear cultures changed the appearance and aroma, which were significantly different from the control cheese. The approach presented in this study represents a method for the development of new cheese varieties with novel aromas within a short ripening time.     

The interaction between yeasts and bacteria in dairy environments

The general environment from which raw dairy products originate and the microbiological quality of the products in its processed state inevitably admit yeast growth and spoilage. Only part of the primary microflora survives under the selective pressures exerted by the intrinsic and extrinsic biotic factors present, processing procedures and preservatives. Yeasts that possess the proper physiological attributes to counteract the specific ecological determinants will be favored. Eventually, a particular yeast community will develop, and if the environmental factors permit, this characteristic yeast community will result in a specific association contributing positively or negatively to the final product. The association that develops between yeasts and bacteria is governed by specific key properties selecting for a few predominant yeasts. These yeasts may either stimulate or inhibit normal bacterial growth. The extent to which interaction between yeasts and bacteria contribute to the final product is discussed.     

The growth, properties and interactions of yeasts and bacteria associated with the maturation of Camembert and blue-veined cheeses

The growth of yeasts and bacteria were monitored during the maturation of Camembert and blue-veined cheese produced in Australia. Yeasts were prominent throughout maturation, growing to 10(5)-10(9)/g, depending on the manufacturer. Debaryomyces hansenii predominated, but there were lesser, inconsistent contributions from Yarrowia lipolytica. Of the non-lactic acid bacteria, Acinetobacter species were significant during the maturation of Camembert but not blue-veined cheeses, and grew to 10(6)-10(8) cfu/g. Staphylococcus and Micrococcus species were consistently isolated from the cheeses with Staphylococcus xylosus growing to 10(5)-10(9) cfu/g, depending on the product. Lactic acid bacteria (10(7)-10(9) cfu/g) were present throughout maturation but were not identified. Interactions between the various yeasts and bacterial isolates were examined. Several strains of D. hansenii exhibited killer activity but not against Y. lipolytica. None of the yeasts were antagonistic towards the bacteria but some strains of D. hansenii enhanced the growth of Y. lipolytica and S. xylosus. The yeast and bacterial isolates exhibited various degrees of extracellular proteolytic and lipolytic activities.     

The occurrence,growth, and biocontrol of Listeria monocytogenes in fresh and surface-ripened soft and semisoft cheeses

Listeria monocytogenes continues to pose a food safety risk in ready-to-eat foods, including fresh and soft/semisoft cheeses. Despite L. monocytogenes being detected regularly along the cheese production continuum, variations in cheese style and intrinsic/extrinsic factors throughout the production process (e.g., pH, water activity, and temperature) affect the potential for L. monocytogenes survival and growth. As novel preservation strategies against the growth of L. monocytogenes in susceptible cheeses, researchers have investigated the use of various biocontrol strategies, including bacteriocins and bacteriocin-producing cultures, bacteriophages, and competition with native microbiota. Bacteriocins produced by lactic acid bacteria (LAB) are of particular interest to the dairy industry since they are often effective against Gram-positive organisms such as L. monocytogenes, and because many LAB are granted Generally Regarded as Safe (GRAS) status by global food safety authorities. Similarly, bacteriophages are also considered a safe form of biocontrol since they have high specificity for their target bacterium. Both bacteriocins and bacteriophages have shown success in reducing L. monocytogenes populations in cheeses in the short term, but regrowth of surviving cells can commonly occur in the finished cheeses. Competition with native microbiota, not mediated by bacteriocin production, has also shown potential to inhibit the growth of L. monocytogenes in cheeses, but the mechanisms are still unclear. Here, we have reviewed the current knowledge on the growth of L. monocytogenes in fresh and surface-ripened soft and semisoft cheeses, as well as the various methods used for biocontrol of this common foodborne pathogen.     

Development of primers for detecting dominant yeasts in smear-ripened cheeses

PCR primers were developed for the specific detection of Clavispora lusitaniae, Debaryomyces hansenii var hansenii, Geotrichum candidum, Kluyveromyces lactis and K. marxianus and Yarrowia lipolytica, yeast species commonly found on the surface of smear cheese. Forty eight representative strains frequently found in smear cheeses or taxonomically related to the target yeasts were used as templates, to validate the designed primers. The specific and selective detection of these yeasts was effective in situ, in Livarot smear, without yeast isolation and culture and was comparable with data obtained with a conventional method. The primers described here have thus potential for PCR studies applied to cheese. It should also be possible to use some of these primers with other substrates.     

Drivers that establish and assembly the lactic acid bacteria biota in cheeses

BackgroundCheeses are inherently microbiologically and biochemically dynamic. Numerous biotic and abiotic drivers govern the establishment and assembly of a core microbiota in cheese, which, for internally-ripened cheeses, having an intermediate to long period of ripening, consists of starter and non-starter lactic acid bacteria (SLAB and NSLAB). The management of this dynamic ecosystem has to consider this core as a super-organism, which results from the sums of microbial metabolisms and interactions among individual microbes.Scope and approachThis review focuses on all presumptive drivers, raw and pasteurized milk, farming system and house microbiota, and intrinsic and extrinsic factors during cheese manufacture and ripening, which qualitatively and mainly depending on the farm management system and cheese variety may influence the populations of SLAB and NSLAB. The interactions between these two microbial groups are described also.Key findings and conclusionsThe cheese ecosystem shows a variable flux of its core microbiota from milking through manufacture to ripening. Many and diverse drivers establish and assembly the lactic acid bacteria biota. If such drivers are efficient to guarantee microbial and cheese diversities, on the other hand, their control is the fundamental pre-requisite to synchronize and balance microbiological events. The methodological approaches (e.g., omics techniques and integrated system biology) have markedly improved to concretize this ambitious goal. Facing and improving the knowledge on the main drivers, the current step should focus on a unique puzzle of coexisting species/biotypes likely a super-organism, whose guide has to consider all casehardened microbial elements.     

Ectoine as a natural component of food: detection in red smear cheeses

Ectoine is a compatible solute accumulated in halophilic bacteria in response to high salt concentrations and offers protection from osmotic stress. The occurrence of compatible solutes is widespread among bacteria, yet ectoine has never been detected in foods. The use of an ectoine producing microorganism (Brevibacterium linens) in the surface ripening of red smear cheeses led to the question whether ectoine can be found in cheese. Therefore we examined samples from a variety of cheese manufacturers and different types of red smear cheeses for the presence of ectoine using HPLC and HPLC/MS analysis. Ectoine solely appears in the rind and was detected up to 178 mg/200 g red smear cheese, depending on several factors like ripening status and conditions throughout the cheese production process (e.g. salt concentrations of used brine baths).     

Potential impact of dairy yeasts on the typical flavour of traditional ewes' and goats' cheeses

The contribution of Debaryomyces hansenii, Kluyveromyces lactis and Kluyveromyces marxianus strains to the typical flavour of traditional ewes' and goats' cheeses was assessed. Fourteen yeast strains were grown in liquid medium mimicking cheese composition and volatile compounds were identified by gas chromatography-mass spectrometry. Yeasts were able to produce key volatile compounds characteristic of the cheeses from which they were isolated. Inter-species and inter-strain variations were observed. Under the conditions tested, D. hansenii produced the lowest levels of volatile compounds, with large intra-strain variations. Kluyveromyces strains primarily produced esters and alcohols. K. marxianus strains were associated with the production of acids, ethyl decanoate, 1-propanol and benzaldehyde, whereas K. lactis was correlated with the presence of ketones, ethyl acetate and secondary alcohols. In conclusion, this study shows the heterogeneous potential of dairy yeasts to contribute to final cheese flavour.     

具有共生关系的乳酸菌和酵母菌的筛选

对分离自酸马奶酒中的9株乳酸菌和8株酵母菌存在共生作用的菌株进行筛选。分别于各自培养基中加入相应的代谢产物,以等量的生理盐水作为对照,测定其稳定期的浊度值和干重值。结果表明:乳酸菌的代谢产物促进的酵母菌生长有12个组合,而接近一半的酵母菌代谢产物对乳酸菌有促进作用。有7个组合的乳酸菌和酵母菌存在共生作用。结论是7个共生组合分别是:LAB2YST4、LAB4YST2、LAB5YST2、LAB7YST2、LAB7YST4、LAB8YST2、LAB9YST2。7个组合中酵母菌YST2和除LAB2外其余的乳酸菌均存在不同程度的共生,共生原因还待进一步研究。     

具有共生关系的乳酸菌和酵母菌的筛选

对分离自酸马奶酒中的9株乳酸菌和8株酵母菌存在共生作用的菌株进行筛选。分别于各自培养基中加入相应的代谢产物,以等量的生理盐水作为对照,测定其稳定期的浊度值和干重值。结果表明:乳酸菌的代谢产物促进的酵母菌生长有12个组合,而接近一半的酵母菌代谢产物对乳酸菌有促进作用。有7个组合的乳酸菌和酵母菌存在共生作用。结论是7个共生组合分别是:LAB2YST4、LAB4YST2、LAB5YST2、LAB7YST2、LAB7YST4、LAB8YST2、LAB9YST2。7个组合中酵母菌YST2和除LAB2外其余的乳酸菌均存在不同程度的共生,共生原因还待进一步研究。      

Inhibition of yeasts isolated from traditional Turkish cheeses by Lactobacillus spp.

Antifungal activity of some Lactobacillus strains was determined. Yeasts were isolated and identified as Saccharomyces cerevisiae (10 of 17) and one each of Candida pseudotropicalis, C. krusei, C. lipolytica, C. lusitaniae, C. ciferrii, Torulopsis glabrata and Rhodotorula rubra . Lactobacillus strains were found to have fairly strong antifungal activity against S. cerevisiae . Of the 19 bacteria tested, L. plantarum Lp 21 seemed to have the most inhibitory effect against all of the S. cerevisiae strains except for S. cerevisiae 13. We suggest that L. plantarum Lp 21 can be used with starter cultures for cheese production.     

Elimination of Listeria monocytogenes in soft and red smear cheeses by irradiation with low energy electrons

Soft and red smear cheeses are frequently contaminated by Listeria monocytogenes , sometimes at relatively high concentration (< 10⁵ CFUg^-1). This bacterium is radiosensitive (D₁₀ value of approximately 0.45 kGy) but irradiation of the whole cheese by X-rays induced off-flavours when the dose exceeded 1.0 kGy. Irradiation could be effective in eliminating L. monocytogenes only from lightly contaminated cheeses (> 10²CFU g^-1).
L. monocytogenes appears only in the rind (where the pH is greater than 6.3) and never grows in the core of the cheese. Under these conditions, a specific irradiation of the rind after ripening, with a low-energy electron beam at relatively high doses (up to 3.0 kGy), allows the total elimination of L. monocytogenes in heavily contaminated samples (10⁵-10⁶ CFU g^-1) without noticeable modifications of the organoleptic properties of the cheese.     

Microbiota dynamics and lactic acid bacteria biodiversity in raw goat milk cheeses

Raw goat milk collected at 11 Andalusian dairy plants was used to individually manufacture cheeses without starter culture addition. Microbial groups were monitored during ripening for 60 days. A total of 1442 lactic acid bacteria (LAB) isolates randomly chosen were identified by molecular methods. Counts of mesophilic LAB exceeded 9 log cfu g⁻¹ on day 1 and decreased 0.5 log units during ripening whereas counts of lactobacilli and leuconostocs increased and those of enterococci remained constant. Thirty-three LAB species belonging to eight different genera were isolated, with higher biodiversity on day 1 (26 species) than on day 60 (20 species). Structural genes coding for nisin, lacticin 481, lactococcin B, six plantaricins and five enterocins were detected in LAB isolates. The information obtained on the technological properties of selected isolates may be useful in developing specific starters for goat milk cheeses, capable of maintaining their distinctive sensory characteristics.     

Interactions between fecal bacteria,bile acids and components of tomato pomace

Food Science and Biotechnology - The tomato pomace obtained during processing as a residue of tomato processing from large industry. The interactions between tomato pomace and fecal bacteria, bile...     

The role of interaction between yeasts and lactic acid bacteria in African fermented milks: a review

Yeasts are present in indigenous African fermented milks in numbers up to log 8 cfu g(-1), together with a varied lactic acid bacteria (LAB) flora, and therefore potentially contribute to product characteristics. However, interaction between yeasts and LAB in these products has received little notice. In studies of indigenous fermented milk in Zimbabwe and Uganda, many samples contained more than one species of yeast, but Saccharomyces cerevisiae was most commonly isolated. Other frequent isolates were other species of Saccharomyces and several species of Candida. Most yeast isolates were lactose-negative but usually galactose-positive. Some strains assimilated lactate and citrate. The growth in milk of strains of yeasts and LAB, isolated from naturally soured milk in Zimbabwe, and their interaction when selected pairs of strains were grown together has been studied. Interactions were shown by the significantly different amounts of certain metabolites produced, such as acetaldehyde and malty aldehydes, when co-cultures were compared to pure cultures. Preliminary sensory acceptance tests did not show, however, that milks made from a co-culture with Candida kefyr and LAB were preferable to the pure LAB culture. Further work is still needed to elucidate the reactions that may be taking place in fermented milk between varying LAB and yeast populations. The potential for use as starter cultures depends on various aspects, including the final product being prepared. The role of other microorganisms in naturally fermented milk also needs to be studied.     

A comparative study of the anti-listerial activity of smear bacteria

Cell-free supernatants from Staphylococcus epidermidis, Staphylococcus warneri and Brevibacterium linens were found to possess anti-listerial activities. Anti-listerial activities were increased during exponential growth phase and reached a maximum during stationary growth phase. S. epidermidis (SE1) and S. warneri (SW1) were found to have particularly high activities against both Listeria monocytogenes and Listeria innocua as inhibition zones for 48 h cell-free supernatants of these strains were found on average to be approximately 10 times larger than those of B. linens (9174, M18 and BL1). Incubation of 48 h cell-free supernatants from S. epidermidis (SE1) and S. warneri (SW1) with proteolytic enzymes (trypsin and pronase E) resulted in a total loss of anti-listerial activity, which revealed its proteinaceous nature, and thus suggested that the observed anti-listerial activities were due to bacteriocin production. The bacteriocins were found to be relatively heat stable and had a molecular mass higher than 30 kDa.