Caracterização bioquímica de cocos Gram-positivos isolados de salame tipo italiano para uso como culturas starter: atividade antagonista, atividade de catalase e de nitrato redutase e produção e degradação de aminas biogênicas / Biochemical characterization of Gram-positive cocci isolated from Italian type sausage for use as starter culture: antagonism, catalase and nitrate reductase activities and production and degradation of biogenic amines

AUTOR(ES)

Inês Helena Tristão de Oliveira

DATA DE PUBLICAÇÃO

2006

RESUMO

Ninety eight strains of Gram-positive bacteria, most of them coagulase- negative staphylococci, originated from Italian type sausages made by artisanal fermentation and industrial fermentation, were characterized in relation to their use as starter cultures. Antagonism to pathogens was evaluated and the possible protein nature of the inhibitory substance was evidenced by reduction of inhibition in presence of protease. Fifty one isolates showed antagonism to Listeria monocytogenes, and 27 of them had their antagonistic action atributed to proteinaceous substance. Thirty seven isolates showed antagonism to Staphylococcus aureus, and 30 of them with antagonistic action related to substance of protein nature. Sixteen strains of staphylococci, from S. capitis subsp. capitis, S. caprae, S. arlettae and S. delphini species exhibited antagonism due to proteinaceous substance against both indicators. All 98 isolates exhibited catalase activity, measured by hydrogen peroxide consumption. Forty six percent of those had high levels of H2O2 degradation, showing values above 28,32 μmoles of degraded H2O2.min-1.mL-1 of cels with OD630nm = 1,0. Sixty eight isolates reduced nitrate in agar with KNO3. Fourty four percent of those had high nitrate reductase activity, showing haloes of nitrate reduction bigger than 12 mm. Eleven isolates originated from artisanal sausages, from S. xylosus, S. arlettae and S. equorum species, presented simultaneously high nitrate reductase and catalase activities, being good candidates as cultures for fermented sausage production. There was a low incidence of genes coding for staphylococcal enterotoxins, detected by PCR, except for the see gene, found in 23,5% of the isolates. Four isolates had both seb and seh genes; two isolates had seh gene; and one isolate had sej gene. The sea, sec and sed genes were not detected in any of the 98 isolates. The see gene was detected in nine of eleven isolates with high nitrate reductase and catalase activities; the others, S. xylosus CIL 28 and S. arlettae CIL 24, had no enterotoxin gene. Biogenic amine production and degradation were quantified by reversed phase ion pair HPLC. Few isolates were found to produce relevant levels of tyramine, histamine, putrescine and cadaverine, and a great number was able to degrade histamine and/or tyramine. Eleven isolates produced values between 2 and 70 mg.L-1 of one or more of the amines and one isolate produced 720,35 mg.L-1 of tyramine. Sixty percent from 98 strains could degrade histamine or tyramine in different degrees. Thirty nine percent of the strains that did not show aminoacid decarboxylase activity on tyrosine, histidine, ornithine or lysine, had the ability to degrade tyramine and histamine. These strains are the most suitable to be used as starter cultures for sausage fermentation. The relevance of this work is the selection of Gram-positive cocci of artisanal origin with biochemical characteristics desired in sausage fermentation. The characterized collection enables a number of combinations between the strains to develop starter cultures. Strains with desired characteristics as good antagonistic ctivity, no production of amines and potential to degrade histamine or tyramine, but low nitrate reductase and catalase activities, can be used together with other strains that complete these characteristics. Even those strains with antagonistic action, which do not produce and/or degrade amines, and have good nitrate reductase and catalase activities, but present enterotoxin genes, can be used as starters if these genes are deleted.

ASSUNTO(S)

salame fermentado gram-positive cocci caracterização bioquímica cocos gram-positivos microbiologia de alimentos fermented sausages biochemical characterization

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