Extracellular expression of a thermostable phytase (phyA) in Kluyveromyces lactis

Abstract

tFunctional expression of a thermostable phytase from A. niger was achieved in Kluyveromyces lactis GG799cells. Effective secretion of recombinant enzyme (198 U ml−1) in the fermentation broth at 72 h incubationat 22◦C was obtained. Purified enzyme showed a specific activity of 72 U mg−1) and was detected on SDS-PAGE as a heavily glycosylated protein with a molecular weight of ≥140 kDa. Optimum temperature ofthe enzyme was at 55◦C and it showed a characteristic bi-hump pH profile with two pH optima (at pH2.5 and 5.5). Enzyme showed considerable pepsin resistance with 60% activity retention after incubationwith pepsin at the ratio of 1:1000. Enzyme was thermostable retaining 69 and 37% activity at 90 and100◦C for 10 min respectively and remained active at these temperatures till 1 h. Deglycosylation studiesdemonstrated negligible effect of N-linked glycans on thermal properties. Multiple sequence alignmentdata revealed a conserved Asn at position 345 of this phytase which might contribute to its thermalproperties. This thermostable phytase coupled with its noticeable protease resistance could be a betteralternative to current commercial phytases.