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vol.46 número1Safety, beneficial and technological properties of Enterococcus faecium isolated from Brazilian cheesesHydroxylation of 1,8-cineole by Mucor ramannianusand Aspergillus niger índice de autoresíndice de assuntospesquisa de artigos
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Brazilian Journal of Microbiology

versão impressa ISSN 1517-8382versão On-line ISSN 1678-4405

Resumo

MONTEIRO, Paulo S.; GUIMARAES, Valéria M.; MELO, Ricardo R. de  e  REZENDE, Sebastião T. de. Isolation of a thermostable acid phytase from Aspergillus niger UFV-1 with strong proteolysis resistance. Braz. J. Microbiol. [online]. 2015, vol.46, n.1, pp.251-260. ISSN 1517-8382.  http://dx.doi.org/10.1590/S1517-838220120037.

An Aspergillus niger UFV-1 phytase was characterized and made available for industrial application. The enzyme was purified via ultrafiltration followed by acid precipitation, ion exchange and gel filtration chromatography. This protein exhibited a molecular mass of 161 kDa in gel filtration and 81 kDa in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), indicating that it may be a dimer. It presented an optimum temperature of 60 °C and optimum pH of 2.0. The KM for sodium phytate hydrolysis was 30.9 mM, while the kcat and kcat/KM were 1.46 ×105 s−1 and 4.7 × 106s−1.M−1, respectively. The purified phytase exhibited broad specificity on a range of phosphorylated compounds, presenting activity on sodium phytate, p-NPP, 2- naphthylphosphate, 1- naphthylphosphate, ATP, phenyl-phosphate, glucose-6-phosphate, calcium phytate and other substrates. Enzymatic activity was slightly inhibited by Mg2+, Cd2+, K+ and Ca2+, and it was drastically inhibited by F−. The enzyme displayed high thermostability, retaining more than 90% activity at 60 °C during 120 h and displayed a t1/2 of 94.5 h and 6.2 h at 70 °C and 80 °C, respectively. The enzyme demonstrated strong resistance toward pepsin and trypsin, and it retained more than 90% residual activity for both enzymes after 1 h treatment. Additionally, the enzyme efficiently hydrolyzed phytate in livestock feed, liberating 15.3 μmol phosphate/mL after 2.5 h of treatment.

Palavras-chave : phosphatase; phytic acid; dephosphorylation.

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