Phytase activity in Cryptococcus laurentii ABO 510

Authors


  • Editor: Hyun Kang

Correspondence: Marinda Viljoen-Bloom, Department of Microbiology, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa. Tel.: +27 21 808 5859; fax: +27 21 808 5846; e-mail: mv4@sun.ac.za

Abstract

Ten Cryptococcus strains were screened for phytase activity, of which the Cryptococcus laurentii ABO 510 strain showed the highest level of activity. The cell wall-associated enzyme displayed temperature and pH optima of 62°C and 5.0, respectively. The enzyme was thermostable at 70°C, with a loss of 40% of its original activity after 3 h. The enzyme was active on a broad range of substrates, including ATP, d-glucose 6-phosphate, d-fructose 1,6-diphosphate and p-nitrophenyl phosphate (p-NPP), but its preferred substrate was phytic acid (Km of 21 μM). The enzyme activity was completely inhibited by 0.5 mM inorganic phosphate or 5 mM phytic acid, and moderately inhibited in the presence of Hg2+, Zn2+, Cd2+ and Ca2+. These characteristics suggest that the Cry. laurentii ABO 510 phytase may be considered for application as an animal feed additive to assist in the hydrolysis of phytate complexes to improve the bioavailability of phosphorus in plant feedstuff.

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