Microbiological characterization of Civil cheese, a traditional Turkish cheese: microbiological quality, isolation and identification of its indigenous Lactobacilli

Summary The aim of this study was to investigate the microbiological quality and the indigenous lactic acid bacteria (Lactobacillus) of Civil cheese. In this study, for identification of lactic acid bacteria isolated from cheese samples, the Microbiology Identification System (MIS) was used. In the samples, average of total aerobic mesophilic bacteria, yeast and moulds, lactic acid bacteria and Staphylococcus aureus (Staph. aureus) were determined to be 3.0×10⁸, 2.0×10⁶, 1.4×10⁷, 4.10×10⁴ c.f.u./g, respectively. Coliform bacteria were lower than <10 c.f.u./g in 26.67 % of the samples. On the other hand, the coliform-positive samples showed an average of 4.2×10⁴ c.f.u./g. Staph. aureus was not detected in 33.33% of Civil cheese samples. Seventy-two strains of Lactobacillus isolated from Civil cheese were identified. Growth at 5, 10 and 37 °C, 2.5% and 6.5% NaCl and gas (CO₂) production from glucose of the isolated strains were also determined. Of the 72 isolates, 20 were identified as Lb. malefermentans, 18 as Lb. fermentum, 17 as Lb. parabuchneri, 10 as Lb. vaccinostercus, 2 as Lb. oris, 1 as Lb. bifermentans, 1 as Lb. delbruecki subsp. bulgaricus, 1 as Lb. cellobiosus, 1 as Lb. hilgardii, 1 as Lb. paracasei subsp. tolerans.     

Microbiological characteristics of Crottin goat cheese made in different seasons

General profiles and effect of season on microbiological characteristics of Crottin goat's cheese were evaluated in different batches during storage. Microorganisms determined were: mesophilic, proteolytic, halotolerant, psychotrophs, coliforms, yeasts and Staphylococcus aureus. The presence of Escherichia coli, Salmonella spp., Yersinia enterocolitica and pH and moisture content were also analyzed. E. coli, Salmonella spp. and Y. enterocolitica were not detected in the Argentinian soft goat cheese. Cheese made during winter had significant differences in mesophilic, psychrotrophics, halotolerant microorganisms and yeast between batches. In fall cheese, there were significant differences to mesophilic, proteolytic and psychrotrophics. There were not significant differences to the microbial groups in summer cheese. The variability between batches in Crottin cheese occurred during cold months, which may be attributed to the coagulation process of the cheese at environmental temperature (without any control), creating a delay in the lactic flora activity in winter. The results showed a significant influence of the seasons in the microbial population evolution during storage, suggesting that the differences in each microbial group in different seasons could be caused by differences in the predominant strains of each group. Further studies are needed for the composition of the microorganisms, where goat's products have not specific hygienic and quality standards in Argentina.     

Microbiological profile in Serra ewes' cheese during ripening

The microflora of Serra cheese was monitored during a 35 d ripening period at three different periods within the ewe's lactation season. After 7 d ripening, the numbers of micro-organisms reached their maximum, and lactic acid bacteria (LAB) and coliforms were the predominant groups. Pseudomonads were not detected after 1 week of ripening. At all stages of ripening, cheeses manufactured in spring exhibited the lowest numbers of LAB and yeasts, whereas cheeses manufactured in winter showed the lowest numbers of coliforms and staphylococci.
Leuconostoc lactis was the most abundant LAB found in Serra cheese whereas Enterococcus faecium and Lactococcus lactis spp. lactis exhibited the highest decrease in percentage composition. Numbers of both Leuc. mesenteroides and Lactobacillus paracasei tended to increase throughout ripening. The most abundant coliform was Hafnia alvei. Klebsiella oxytoca was found in curd but declined in number during ripening. Staphylococcal flora of curd was mainly composed of Staphylococcus xylosus, Staph. aureus and Staph. epidermidis. Staphylococcus xylosus was the major species found at the end of ripening. Pseudomonas fluorescens , was the only Pseudomonas species isolated from the curd. Although a broad spectrum of yeasts were found in Serra cheese, Sporobolomyces roseus was the most abundant yeast isolated.     

北疆传统发酵生奶酪中乳酸菌的耐受性及益生特性测定

【背景】北疆乳制品中生奶酪作为发酵乳制品,其中有多种微生物的参与,是优质食品级微生物的宝贵来源,然而其中蕴含的丰富的微生物资源也面临着流失。【目的】研究已筛选出的41株乳酸菌的生长曲线变化规律,并对其在低pH环境的耐酸特性及益生特性进行分析。【方法】通过人工模拟胃肠液和含0.3%、0.5%、1.0%浓度牛胆盐溶液培养,对从生奶酪中分离鉴定的41株乳酸菌菌株进行人工胃肠液、牛胆盐耐受性试验。【结果】41株乳酸菌中有6株乳酸菌(编号为QM-5、QM-27、UM-12、UM-18、NM-11和NM-14)均能在pH值分别为2.0、2.5、3.0、3.5、4.0时生长较好,在pH 2.0的环境下也保持一定程度的生长。菌株存活率大于50%,乳酸菌含量为108 CFU/mL以上。从生奶酪分离的乳酸菌有极强的耐酸、耐胆盐特性,可以预测在胃肠道环境生存。41株菌对大肠杆菌(Escherichia coli)、金黄色葡萄球菌(Staphylococcus aureus)和枯草芽孢杆菌(Bacillus subtilis)均有抑制作用。【结论】通过比较耐酸性、胃肠道模拟、胆盐耐受性和抑菌特性等实验结果,初...     

Biodiversity of bacterial ecosystems in traditional Egyptian Domiati cheese

Bacterial biodiversity occurring in traditional Egyptian soft Domiati cheese was studied by PCR-temporal temperature gel electrophoresis (TTGE) and PCR-denaturing gradient gel electrophoresis (DGGE). Bands were identified using a reference species database (J.-C. Ogier et al., Appl. Environ. Microbiol. 70:5628-5643, 2004); de novo bands having nonidentified migration patterns were identified by DNA sequencing. Results reveal a novel bacterial profile and extensive bacterial biodiversity in Domiati cheeses, as reflected by the numerous bands present in TTGE and DGGE patterns. The dominant lactic acid bacteria (LAB) identified were as follows: Leuconostoc mesenteroides, Lactococcus garvieae, Aerococcus viridans, Lactobacillus versmoldensis, Pediococcus inopinatus, and Lactococcus lactis. Frequent non-LAB species included numerous coagulase-negative staphylococci, Vibrio spp., Kocuria rhizophila, Kocuria kristinae, Kocuria halotolerans, Arthrobacter spp./Brachybacterium tyrofermentans. This is the first time that the majority of these species has been identified in Domiati cheese. Nearly all the dominant and frequent bacterial species are salt tolerant, and several correspond to known marine bacteria. As Domiati cheese contains 5.4 to 9.5% NaCl, we suggest that these bacteria are likely to have an important role in the ripening process. This first systematic study of the microbial composition of Domiati cheeses reveals great biodiversity and evokes a role for marine bacteria in determining cheese type.     

一株分离自胡杨的赖氨酸芽孢杆菌(Lysinibacillus)ML-64的微生物学特性

摘要:【目的】从胡杨茎秆液中分离得到的一株菌株ML-64,对其进行微生物学特性的分析。【方法】通过细菌培养和染色的方法进行了形态和培养特征的检测,使用多相分类学方法测定菌株的各项生理生化指标,脂肪酸组分、醌组分、极性脂类型、16S rRNA基因系统发育分析、(G+C)mol%含量的测定和DNA-DNA杂交分析。【结果】菌株ML-64为革兰氏阳性菌,杆状,产生芽孢。菌落为圆形,淡黄色,表面光滑。菌株生长温度范围为10－45℃(最适37℃),pH范围为7.0－9.0(最适pH7.0),NaCl浓度范围为0－6%(W/V) (最适0－2%)。菌株ML-64 的类脂酯酶,精氨酸双水解酶,脲酶活性和VP-实验为阳性。在API 50CH酶活性检测实验中菌株不能发酵任何糖类。可利用的碳源有: L-丝氨酸,丙酮酸甲酯,α-酮-丁酸,乙酰乙酸。对多粘菌素B(30 μg)、新生霉素(30 μg)、青霉素G(10 U)不敏感。16S rRNA基因序列分析结果表明,菌株ML-64T与ysinibacillus chungkukjangi 2RL3-2T,Lysinibacillus sinduriensis BLB-1T有密切亲缘关系。相似率分别为100%和99.1%。菌株ML-64与Lysinibacillus chungkukjangi 2RL3-2T和Lysinibacillus massiliensis CIP108446T之间的杂交率分别为82%和50.9%。基因组DNA(G+C)mol%含量为36.8%。菌株ML-64优势脂肪酸类型为iso-C15:0(55.05%)和anteiso-C15:0(20.70%),醌组分类型是MK-7。【结论】基于表型特征、遗传型特征和系统发育分析,将菌株定为Lysinibacillus chungkukjangi的新变种,获得序列注册号为KC609752。胡杨内生菌ML-64的基因组结构已与最近源菌株L．chungkukjangi产生了较大的分化,选择性地适应了胡杨内生环境。     

PCR-DGGE fingerprints of microbial succession during a manufacture of traditional water buffalo mozzarella cheese

AIMS: To monitor the process and the starter effectiveness recording a series of fingerprints of the microbial diversity occurring at different steps of mozzarella cheese manufacture and to investigate the involvement of the natural starter to the achievement of the final product. METHODS AND RESULTS: Samples of raw milk, natural whey culture (NWC) used as starter, curd after ripening and final product were collected during a mozzarella cheese manufacture. Total microbial DNA was directly extracted from the dairy samples as well as bulk colonies collected from the plates of appropriate culture media generally used for viable counts of mesophilic and thermophilic lactic acid bacteria (LAB) and used in polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) experiments. The analysis of the DGGE profiles showed a strong influence of the microflora of the NWC on the whole process because after the starter addition, the profile of all the dairy samples was identical to the one shown by the NWC. Simple indexes were calculated for the DGGE profiles to have an objective estimation of biodiversity and of technological importance of specific groups of organisms. LAB grown on Man Rogosa Sharp (MRS) and Rogosa agar at 30 degrees C showed high viable counts and the highest diversity in species indicating their importance in the cheese making, which had not been considered so far. Moreover, the NWC profiles were shown to be the most similar to the curd profile suggesting to be effective in manufacture. CONCLUSIONS: The PCR-DGGE analysis showed that in premium quality manufacture the NWC used as starter had a strong influence on the microflora responsible for process development. SIGNIFICANCE AND IMPACT OF THE STUDY: The molecular approach appeared to be valid as a tool to control process development, starter effectiveness and product identity as well as to rank cheese quality.     

Antilisterial activity of lactic acid bacteria isolated from rigouta, a traditional Tunisian cheese

AIMS: Screening for lactic acid bacteria (LAB) producing bacteriocins and other antimicrobial compounds is of a great significance for the dairy industry to improve food safety. METHODS AND RESULTS: Six-hundred strains of LAB isolated from 'rigouta', a Tunisian fermented cheese, were tested for antilisterial activity. Eight bacteriocinogenic strains were selected and analysed. Seven of these strains were identified as Lactococcus lactis and produced nisin Z as demonstrated by mass spectrometry analysis of the purified antibacterial compound. Polymerase chain reaction experiments using nisin gene-specific primers confirmed the presence of nisin operon. Plasmid profiles analysis suggests the presence of, at least, three different strains in this group. MMT05, the eighth strain of this antilisterial collection was identified, at molecular level, as Enterococcus faecalis. The purified bacteriocin produced by this strain showed a molecular mass of 10 201.33 +/- 0.85 Da. This new member of class III bacteriocins was termed enterocin MMT05. CONCLUSIONS: Seven lactococcal strains producing nisin Z were selected and could be useful as bio-preservative starter cultures. Additional experiments are needed to evaluate the promising strain MMT05 as bio-preservative as Enterococci could exert detrimental or beneficial role in foods. SIGNIFICANCE AND IMPACT OF THE STUDY: Only a few antibacterial strains isolated from traditional African dairy products were described. The new eight strains described herein contribute to the knowledge of this poorly studied environment and constitute promising strains for fermented food safety.     

Effect of curd-cooking temperatures on the microbiological quality ofayib,a traditional Ethiopian cottage cheese

Ayib was made following traditional methods of curd cooking at 40°, 50°, 60° and 70°C requiring 10 h, 7 h, 145 min and 55 min, respectively. During the natural fermentation of raw milk into sour milk (curd), the count of all groups of microorganisms increased by at least a 100-fold. When the curd was subsequently cooked at 40°C, counts of enterococci and members of Enterobacteriaceae decreased by a 100-fold and lactic acid bacteria and staphylococci by a 100-fold. At 50°C, the count of enterococci, members of Enterobacterlaceae and staphylococci was lower than could be detected (<10² c.f.u./g). Yeasts, moulds and lactic acid bacteria still had counts of about 10⁵ c.f.u./g. The total aerobic count decreased by a 100-fold but was still high (>10⁷ c.f.u./g). At 60°C, yeasts and moulds decreased by 1000-fold and at 70°C they decreased below detectable levels (<10² c.f.u./g). This latter temperature is thus recommended as it results in a less contaminated and saferayib.

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Résumé On a préparél'Ayib selon les méthodes traditionnelies de cuission du lait caillé à 40, 50, 60 et 70°C, ce qui a requis respectivement 10 h, 7 h, 145 et 55 min. Durant la fermentation naturelle du lait frais en lait caillé, le décompte de tous les groupes de microorganismes a crû d'au moins 100 fois. Quand le lait caillé était par la suite cuit à 40°C, le décompte des entérocoques et des membres des Enterobacteriaceae a décru de 100 fois et celui des bactéries lactiques et des staphylocoques de 100 fois. A 50°C, le décompte des entérocoques, membres des Enterobacteriaceae et des staphylocoques était inférieur au seuil de détection (<10² c.f.u./g). Les levures, moisissures et bactéries lactiques avalent toujours un décompte d'environ 10⁵ c.f.u./g. le décompte total aérobie décroissait de 100 fois mais restait néanmoins élevé (>10⁷ c.f.u./g.). A la température de cuisson du lait caillé de 60°C, les levures et les moisissures ont décru de 1000 fois, et à 70°C on décru au dessous du seuil de détection (<10² c.f.u./g). Cette dernière température est donc recommandable car elle résulte en unayib moins contaminé et plus sain.

     

Our ancestors' ancestor: Ouranopithecus is a greek link in human ancestry

Recent discoveries of the late Miocene hominoid Ouranopithecus shed new light on the evolution of hominids. These discoveries result from the strategy of the Allied armies during the First World War. In the midst of “the war to end all wars,” the North African soldiers of Camille Arambourg excavated the first mammalian fossils found in northern Greece, in the region of Macedonia, the country of Alexander the Great. On the tracks of these strange paleontological pioneers, a modern French and Greek team has unearthed a large hominoid primate, a missing link between fossilapes and primitive Australopithecus, which lived in southeastern Europe 9 to 10 million years ago. A reconstruction of Ouranopithecus and its surroundings gives us a rare glimpse into the world of the earliest hominids.     

Biodiversity in Oscypek, a traditional Polish cheese, determined by culture-dependent and -independent approaches

Oscypek is a traditional Polish scalded-smoked cheese, with a protected-designation-of-origin (PDO) status, manufactured from raw sheep's milk without starter cultures in the Tatra Mountains region of Poland. This study was undertaken in order to gain insight into the microbiota that develops and evolves during the manufacture and ripening stages of Oscypek. To this end, we made use of both culturing and the culture-independent methods of PCR followed by denaturing gradient gel electrophoresis (PCR-DGGE) and pyrosequencing of 16S rRNA gene amplicons. The culture-dependent technique and PCR-DGGE fingerprinting detected the predominant microorganisms in traditional Oscypek, whereas the next-generation sequencing technique (454 pyrosequencing) revealed greater bacterial diversity. Besides members of the most abundant bacterial genera in dairy products, e.g., Lactococcus, Lactobacillus, Leuconostoc, Streptococcus, and Enterococcus, identified by all three methods, other, subdominant bacteria belonging to the families Bifidobacteriaceae and Moraxellaceae (mostly Enhydrobacter), as well as various minor bacteria, were identified by pyrosequencing. The presence of bifidobacterial sequences in a cheese system is reported for the first time. In addition to bacteria, a great diversity of yeast species was demonstrated in Oscypek by the PCR-DGGE method. Culturing methods enabled the determination of a number of viable microorganisms from different microbial groups and their isolation for potential future applications in specific cheese starter cultures.     

Behaviour of Listeria monocytogenes during the traditional manufacture of water-buffalo Mozzarella cheese

F. VILLANI, O. PEPE, G. MAURIELLO, G. MOSCHETTI, L. SANNINO AND S. COPPOLA. 1996. The behaviour of a four-strains mixture of Listeria monocytogenes (strains Scott A, V7, OH and Cal) during the traditional manufacture of water-buffalo Mozzarella cheese was investigated at two levels of inoculation: ca 10⁵and 10³cfu ml^-1of vat milk. No significant change in Listeria counts was observed during the curd ripening (4.0–4.5 h), at the end of which the pH ranged between 4.83 and 4.91. A decrease of about 2 log was observed after stretching of the curd in hot water (95°C), followed by complete elimination of Listeria after 48 and 24 h of storage of the final cheese in the conditioning liquid (skim water resulting from the stretching, pH ca 4.0) with initial high and low contamination of the cheese milk respectively. Results also indicated that a 1.7 log reduction of L. monocytogenes could be achieved during the preparation of the natural whey culture utilized as starter in cheesemaking.     

Microbiological characteristics of Pacific shrimp (Pandalus jordani).

Microorganisms associated with Pacific shrimp (Pandalus jordani) were isolated and identified. Those on the iced raw shrimp, which yielded an average count of 1.6 x 10(6), were predominantly Moraxella, Pseudomonas, Acinetobacter, Arthrobacter, and Flavobacterium-Cytophaga spp. The blanching and peeling reduced the microbial level to 3.3 x 10(4) and also selectively eliminated Moraxella spp. The microbial flora changed after each processing sequence, and the heat sensitivity and growth characteristics of the representative microbial groups suggested that the presence of Arthrobacter and Acinetobacter spp. in peeled shrimp may indicate inadequate cleaning of raw shrimp or a shorter blanching time. The presence of Moraxella and Flavobacterium-Cytophaga spp. would indicate the degree of secondary contamination, and the presence of Pseudomonas spp. would indicate the shelf-age of the processed shrimp.