Proteolytic activity among psychrotrophic bacteria isolated from refrigerated raw milk

Nörnberg, Maria F B L; Friedrich, Rosane Salete; Weiss, Rita Denise Niederauer; Tondo, Eduardo César; Brandelli, Adriano

doi:10.1111/j.1471-0307.2009.00542.x

Cited by 55 publications

(51 citation statements)

References 31 publications

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“…Detection of S. liquefaciens, K. oxytoca and H. alvei in our study is of commercial significance in milk. Their presence in milk has not only been linked to undesirable alteration in appearance and flavours but also to residual activity of enzymes such as proteases which have been associated with gelation of milk and coagulation of milk proteins during storage (Nornberg et al, 2010). We identified six different species of the genus Enterobacter from PDBM, however, E. cloacae and E. asburiae were detected at higher prevalence.…”

Section: Identification and Characterization Of Bacterial Speciesmentioning

confidence: 93%

Characterization of Escherichia coli and other Enterobacteriaceae in producer-distributor bulk milk

Ntuli

Njage

Buys

2016

Journal of Dairy Science

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INTERPRETIVE SUMMARYCharacterization of E. coli and other Enterobacteriaceae in producer-distributor bulk milk, Ntuli, The direct sale of milk from producer-distributor (PD) to consumers is a common practice in many countries. We characterized E. coli and other Enterobacteriaceae in PD bulk milk sold at retail points in South Africa (SA). The study highlighted that there is a potential risk of transferring drug resistant pathogenic E. coli to consumers through the food chain.Information obtained from the study will be used to model the risk of pathogenic E. coli in PD milk and the proposal of most potentially effective mitigation efforts towards enhancing food security. ABSTRACTThe current study was undertaken to characterize Escherichia coli and other Enterobacteriaceae in raw and pasteurized producer-distributor bulk milk (PDBM). A total of 258 samples were collected from purchase points in 8 provinces in South Africa. The samples were tested for 1 antibiotic residues, phosphatase, total aerobic bacteria, coliforms and E. coli counts. Matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used for identification of isolates. E. coli isolates were characterized for virulence factors, antimicrobial resistance, serotypes and presumptive E. coli O157:H7. Antibiotic residues and alkaline phosphatase were detected in 2 % (n=258) and 21 % (n=104) of the samples respectively. A total of 729 isolates belonging to 21 genera and 59 species were identified. E. coli, Enterobacter cloacae, Klebsiella oxytoca and Raoultella ornithinolytica were the most abundant species. Spoilage Enterobacteriaceae species exceeded 50 % of the total isolates. E. coli was detected and isolated from 36 % of the milk samples. Thirty one E. coli isolates harbored virulence genes stx1/stx2 and 38 % (n=121) were presumptive O157:H7. Prevalence of samples with presumptive shigatoxin producing E. coli (STEC) was 10 %. Antimicrobial resistant E. coli isolates were detected in 70 % of the milk samples with 36 % of stx1/stx2 positive E. coli showing multi-drug resistance. Information obtained from the study will be used for modelling the public health risk posed by milkborne pathogens in PDBM, which in many cases is consumed by the poor and vulnerable population.

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Section: Identification and Characterization Of Bacterial Speciesmentioning

confidence: 93%

Characterization of Escherichia coli and other Enterobacteriaceae in producer-distributor bulk milk

Ntuli

Njage

Buys

2016

Journal of Dairy Science

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“…However, some bacterial enzymes are heat-resistant and retain their activity over a broad range of temperatures and water activities (Chen, Daniel, & Coolbear, 2003;Marchand et al, 2009a;Nörnberg, Friedrich, Weiss, Tondo, & Brandelli, 2010). Even though enzymes present in processed milk and milk products can be present at low concentrations, over time these enzymes will alter the physico-chemical properties of the finished dairy product, which can alter the product's functionality and sensory properties (Celestino, Iyer, & Roginski, 1997a;GuinotThomas, Alammoury, & Laurent, 1995).…”

Section: Introductionmentioning

confidence: 95%

Thermo-resistant enzyme-producing bacteria isolated from the internal surfaces of raw milk tankers

Teh

Flint

Palmer

et al. 2011

International Dairy Journal

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“…Na literatura, os valores de psicrotróficos com capacidade de clivar frações proteicas convergem para algo em torno do valor de 40 a 45% de psicrotróficos proteolíticos (Silveira et al, 1998;Martins et al, 2006;Nörnberg et al, 2010).…”

Section: Resultsunclassified

“…Pseudomonas é o psicotrófico clássico, de todos os micro-organismos presentes no leite é o que possui a maior atividade metabólica (tendendo à lipolítica) na faixa de temperatura de 4°C a 7°C (Nörnberg et al, 2010). Por outro lado, os Bacillus são predominantes em temperaturas de resfriamento marginal, de 8 a 10°C, e, embora aproveitem frações graxas, o metabolismo proteolítico prevalece (Sørhaug & Stepaniak, 1997;Zacharov & Helpern, 2007).…”

Section: Introductionunclassified

Atividade proteolítica de bactérias psicrotróficas em leites estocados em diferentes temperaturas

et al. 2013

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Proteolytic activity of psychrotrophic bacteria in milk stored at different temperaturesThe widespread use of cooling technology as a tool for maintaining the microbiological and organoleptic characteristics of milk, Without effective hygienic practices throughout the milk production, caused the psychrotrophic micro-organisms to become major deteriorative bacteria in the dairy industry. The present study aimed to assess how the proteolytic psychrotrophic metabolism responds to different milk storage temperatures, drawing a parallel among psychrotrophic growth, amount of micro-organisms capable of breaking down proteins and amount of GMP (glycomacropeptide) released. Milk samples were collected directly from the cooling tank and subjected to count of psychrotrophs, count of proteolytic micro-organisms and the concentration of GMP at different storage times and temperatures. There was no linearity between the microbiological parameters and the GMP measured, according to the time/temperature binomial. The highest concentration of GMP (5.07 mg/mL) was measured in the binomial 8°C/24h (T8/ M24). The data make clear the need for further studies about questions involving the psychrotrophic microbiota in order to clarify extremely important basic questions about their metabolism.

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Proteolytic activity among psychrotrophic bacteria isolated from refrigerated raw milk

Cited by 55 publications

References 31 publications

Characterization of Escherichia coli and other Enterobacteriaceae in producer-distributor bulk milk

Characterization of Escherichia coli and other Enterobacteriaceae in producer-distributor bulk milk

Thermo-resistant enzyme-producing bacteria isolated from the internal surfaces of raw milk tankers

Atividade proteolítica de bactérias psicrotróficas em leites estocados em diferentes temperaturas

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