scholarly journals A Novel qPCR Method for the Detection of Lactic Acid Bacteria in Fermented Milk

Foods ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3066
Author(s):  
Xiankang Fan ◽  
Xiefei Li ◽  
Tao Zhang ◽  
Jue Xu ◽  
Zihang Shi ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Fermented Milk ◽  
Confocal Laser ◽  
Quantitative Detection ◽  
Rrna Gene ◽  
Detection Range ◽  
Qualitative And Quantitative ◽  
Tuf Gene ◽  
Qpcr Method

The number of live lactic acid bacteria (LAB) is an important quality indicator for yogurt, the quantitative testing of LAB has become an important task in the evaluation of product quality and function. By analyzing and comparing the performance of 16S rRNA gene and tuf gene used in absolute quantification, the tuf gene with copy number 1 was selected as the target gene of six LAB. By drawing a standard curve to achieve qualitative and quantitative detection of six strains of LAB, the detection range was found to be 1 × 103–1 × 108 copies/µL. The traditional plate colony count and Flow Cytometry (FCM) were compared with the method of qPCR, which was used in this experiment. Meanwhile, the confocal laser microscope combined with STYO 9 and propidium iodide dyes was used to determine that the content of viable bacteria in the yogurt was more than 90%, which proved that the detection result using qPCR method was closer to the true level of LAB in yogurt. Compared with the existing methods, the method in this study allowed the qualitative and quantitative detection of the six kinds of LAB in yogurt, and the distribution of live and dead bacteria in yogurt could be calculated.

Study on molecular identification of lactic acid bacteria from fermented milks and “Smen” (a traditional steppe butter) and their enzyme producing attributes

2019 ◽  
Vol 9 (3) ◽  
pp. 95-103
Author(s):  
Asmaa Labtar ◽  
Saliha Larouci ◽  
Amel Guermouche ◽  
Farid Bensalah
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Pcr Amplification ◽  
Titratable Acidity ◽  
Streptococcus Thermophilus ◽  
Fermented Milk ◽  
Rrna Gene ◽  
Bacterial Strains ◽  
Search Tool ◽  
Fermented Dairy

Streptococcus thermophilus and Lactobacillus belong to a widely-knowngroup of bacteria that have been frequently used as starter bacteria in fermented dairy products. The aim of this study was to isolate, characterize andidentify of lactic acid bacteria (LAB) from raw cow’s fermented milk and‘Smen’ (a traditional steppe butter) in steppic area of Algeria to study someof their important enzyme-producing attributes. All selected strains of lacticacid bacteria (LAB) were identified and typed by phenotypic and genotypiccriteria.Six strains were identified as cocci thermophilic LAB and two of themwere selected and identified by using polymerase chain reaction (PCR) amplification for proA gene. Six strains of lactobacilli were identified as Lactobacillus genus using 16S rRNA gene. Species identification was performed by 16SrRNA gene sequencing and sequences were analysed using Basic LengthAlignment Search Tool (BLAST) programs. A phylogenetic tree based on 16SrRNA genes was constructed by the neighbor-joinin method.S. thermophilusstrains screened for their ability to produce lactic acid, titratable acidity, andpH was measured at 2h intervals, proteolytic activity in milk was examined.In another part, the four selected Lactobacillus were able to hydrolyze X-Galby production of β-galactosidase enzyme. All strains of LAB exhibited production of diacetyl. Overall, this study provides bacterial strains having potentialfor dairy industry.

scholarly journals Rep PCR Characterization of Lactic Acid Bacteria Isolated From Raw Cows’ Milk in Algeria.

2021 ◽  
Author(s):  
Akil LOMANI ◽  
Dennis S Nielsen ◽  
Larbi Ahmed Amine ◽  
Tahri Ahmed ◽  
Mediani Ahmed
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Bile Salts ◽  
Acid Tolerance ◽  
16S Rrna Gene Sequencing ◽  
Fermented Milk ◽  
Haemolytic Activity ◽  
Rrna Gene ◽  
Rrna Gene Sequencing

Abstract Milk and indigenous fermented, milk based products are a rich source of lactic acid bacteria (LAB) and may serve as a source of potential probiotics. In the present study LAB were isolated from raw cows’ milk sampled at five different Algerian farms. A total of 24 Gram positive, catalase negative isolates where identified to species level using a combination of (GTG) 5-based rep-PCR fingerprinting and 16S rRNA gene sequencing. All isolates were identified as Enterococcus faecium and all isolates had highly similar rep-PCR profiles. Four representative isolates were screened for acid tolerance, bile salts tolerance, antimicrobial susceptibility, antibacterial activity and haemolysis. The four selected strains all exhibited good tolerance to low pH (2, 3, and 4), and to bile salts (concentrations of 0.5%, 1%, and 2%) and were sensitive to chloramphenicol, vancomycin, tetracycline, gentamicine and peniciline G, but were resistant to oxaciline. Cell-free supernatants of the four tested strains all inhibited Staphylococcus aureus, Escherichia coli and Listeria monocytogenes but not Salmonella Typhi. No haemolytic activity was observed.

scholarly journals Isolation and Characterization of Lactic Acid Bacteria and Yeasts from Typical Bulgarian Sourdoughs

2021 ◽  
Vol 9 (7) ◽  
pp. 1346
Author(s):  
Mariana Petkova ◽  
Petya Stefanova ◽  
Velitchka Gotcheva ◽  
Angel Angelov
Keyword(s):  
Lactic Acid ◽  
Sequence Analysis ◽  
Lactic Acid Bacteria ◽  
Antimicrobial Properties ◽  
Matter Content ◽  
Starter Cultures ◽  
Rrna Gene ◽  
Dry Matter Content ◽  
Isolation And Characterization ◽  
Selection Of

Traditional sourdoughs in Bulgaria were almost extinct during the centralized food production system. However, a rapidly developing trend of sourdough revival in the country is setting the demand for increased production and use of commercial starter cultures. The selection of strains for such cultures is based on geographical specificity and beneficial technological properties. In this connection, the aim of this study was to isolate, identify and characterize lactic acid bacteria (LAB) and yeasts from typical Bulgarian sourdoughs for the selection of strains for commercial sourdough starter cultures. Twelve samples of typical Bulgarian sourdoughs were collected from different geographical locations. All samples were analyzed for pH, total titratable acidity and dry matter content. Enumeration of LAB and yeast was also carried out. Molecular identification by 16S rDNA sequence analysis was performed for 167 LAB isolates, and 106 yeast strains were identified by ITS1-5.8S-ITS2 rRNA gene partial sequence analysis. The LAB strains were characterized according to their amylolytic and proteolytic activity and acidification capacity, and 11 strains were selected for further testing of their antimicrobial properties. The strains with the most pronounced antibacterial and antifungal activity are listed as recommended candidates for the development of starter cultures for sourdoughs or other food products.

scholarly journals Effects of ultrasound on the fermentation profile of fermented milk products incorporated with lactic acid bacteria

2019 ◽  
Vol 90 ◽  
pp. 1-14 ◽  
Author(s):  
A.M.N.L. Abesinghe ◽  
N. Islam ◽  
J.K. Vidanarachchi ◽  
S. Prakash ◽  
K.F.S.T. Silva ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Fermented Milk ◽  
Milk Products ◽  
Fermentation Profile ◽  
Fermented Milk Products

Screening for antimicrobial and proteolytic activities of lactic acid bacteria isolated from cow, buffalo and goat milk and cheeses marketed in the southeast region of Brazil

2015 ◽  
Vol 83 (1) ◽  
pp. 115-124 ◽  
Author(s):  
Fabricio L Tulini ◽  
Nolwenn Hymery ◽  
Thomas Haertlé ◽  
Gwenaelle Le Blay ◽  
Elaine C P De Martinis
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Proteolytic Activity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Fermented Milk ◽  
Antimicrobial Activities ◽  
Penicillium Expansum ◽  
Streptococcus Uberis ◽  
Sds Page

Lactic acid bacteria (LAB) can be isolated from different sources such as milk and cheese, and the lipolytic, proteolytic and glycolytic enzymes of LAB are important in cheese preservation and in flavour production. Moreover, LAB produce several antimicrobial compounds which make these bacteria interesting for food biopreservation. These characteristics stimulate the search of new strains with technological potential. From 156 milk and cheese samples from cow, buffalo and goat, 815 isolates were obtained on selective agars for LAB. Pure cultures were evaluated for antimicrobial activities by agar antagonism tests and for proteolytic activity on milk proteins by cultivation on agar plates. The most proteolytic isolates were also tested by cultivation in skim milk followed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of the fermented milk. Among the 815 tested isolates, three of them identified asStreptococcus uberis(strains FT86, FT126 and FT190) were bacteriocin producers, whereas four other ones identified asWeissella confusaFT424,W. hellenicaFT476,Leuconostoc citreumFT671 andLactobacillus plantarumFT723 showed high antifungal activity in preliminary assays. Complementary analyses showed that the most antifungal strain wasL. plantarumFT723 that inhibitedPenicillium expansumin modified MRS agar (De Man, Rogosa, Sharpe, without acetate) and fermented milk model, however no inhibition was observed againstYarrowia lipolytica. The proteolytic capacities of three highly proteolytic isolates identified asEnterococcus faecalis(strains FT132 and FT522) andLactobacillus paracaseiFT700 were confirmed by SDS–PAGE, as visualized by the digestion of caseins and whey proteins (β-lactoglobulin and α-lactalbumin). These results suggest potential applications of these isolates or their activities (proteolytic activity or production of antimicrobials) in dairy foods production.

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