Cloning and Characterization of a β-Propeller Phytase from the Spore-Forming Bacillus paralicheniformis T7 Strain

Phytases are industrial enzymes that enhance the availability of phytate-bound phosphorus and can reduce the environmental burden associated with undigested phytate. Bacillus paralicheniformis T7 is a spore-forming strain exhibiting multiple hydrolytic activities, including phytase activity. The phyL gene encoding β-propeller phytase was cloned from B. paralicheniformis T7 and expressed in Escherichia coli, followed by purification and biochemical characterization of the recombinant enzyme—rPhyL. The molecular mass of rPhyL was 41.0 kDa, and maximal activity was observed at pH 8.0 and 60 °C. The enzyme displayed alkaline stability, retaining 90% and 93% of its initial activity after 5 h at pH 8.0 and 10.0, respectively. Following 5 h of incubation at 50 °C and 55 °C, residual activities were 83% and 46%, respectively. rPhyL was strongly Ca2+-dependent, with maximal activity at 0.6–1.0 mM CaCl2. Kinetic analysis using sodium phytate as the substrate yielded an apparent Km of 1.21 mM, an apparent Vmax of 328.6 μM·min−1, and an apparent Ki of 1.34 mM under the specified assay conditions. Under the tested conditions, rPhyL exhibited detectable activity toward sodium phytate, whereas no detectable activity was observed toward ATP, sodium pyrophosphate, β-glycerophosphate, or p-nitrophenyl phosphate. These findings characterize rPhyL as a Ca2+-dependent bacillary β-propeller phytase with alkaline stability, expanding the enzymatic repertoire of the spore-forming B. paralicheniformis T7 strain.