Ethanol dehydrogenase activity in starter cultures for yoghurt under cold storage conditions / Atividade de etanol desidrogenase durante a estocagem em culturas usadas na produção de iogurte

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

Alcohol dehydrogenase, ADH, activity was investigated in Streptococcus thermophilus NCDO 1968, Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842, Lactobacillus acidophilus ATCC 4356, and the probiotic strain Lactobacillus delbrueckii UFV H2b20, after growth at 37C for 12 hours, and storage at 4C for 21 days. L. delbrueckii subsp. bulgaricus and L. acidophilus presented positive results for ADH activity in Alcohol Indicator Medium, while L. delbrueckii UFV H2b20 presented negative results after 21 days. This method was not discriminatory for S. thermophilus. ADH activity was also measured by the oxidation of NAD(P)H and expressed as μmol of NAD(P)H oxydized per min per mg protein. The average activity in L. acidophilus was 1,06x10-7 mol.min-1.mg-1. The activity increased to 9,17x10-7mol.min-1.mg-1 after cells were kept in MRS medium at 4C, for 5 days. Increases in ADH activity were also detected in cell free extracts of L. delbrueckii subsp. bulgaricus and S. thermophilus. The three strains displayed low ADH activity in MRS broth after 21 days at 4C. The headspace analysis by Gas Chromatography/ Mass Spectroscopy revealed acetaldehyde production by L. delbrueckii subsp. bulgaricus, L. acidophilus and S. thermophilus. The latter produced acetaldehyde only after storage at 4C. Ethanol production was not detected. Despite some ADH activity was detected in liquid medium, the combined results do not support completely the hypothesis that ADH activity would be induced itself after storage at low temperatures. Other studies are still needed.

ASSUNTO(S)

cultura láctea ethanol dehydrogenase iogurte etanol desidrogenase microbiologia agricola starter cultures yoghurt

ACESSO AO ARTIGO

Documentos Relacionados