Heterologous expression and biophysical characterization of a mesophilic tannase following manganese nanoparticle immobilization

In the current study, we analyzed the efficacy of manganese oxide nanoparticle (MnNP)-water dispersion as an immobilization matrix for bacterial tannase. The tannase-secreting Bacillus subtilis strain NJKL.tan.2 obtained from tannery effluent soil was subsequently purified and cloned in pET20b vector. The activity of MnNP-tan (tannase activated by manganese nanoparticles) was 1.51- and 3.5-fold higher at 20 °C and 80 °C, respectively, compared with the free enzyme. MnNP-tan decreased K_m by 41.66 % and 3-fold, whereas free tannase showed two-fold and six-fold improvement in K_cat at 37 °C and 80 °C, respectively. MnNP-tan showed an increase in (half-life)t_1/2 and E_d by 13-fold and 50.05 units, respectively, at 80 °C, in contrast to the native enzyme. MnNP-tan retained its residual activity by 78.2 % at 37 °C and 34.24 % at 80 °C after 180 min of incubation when compared with untreated set. MnNP-tan retained 51 % of its activity after 120 days with the native enzyme losing ∼50 % functionality following 40 days of incubation. The MnNP-mediated tannase immobilization technique is being reported for the first time. The technique has numerous advantages due to the use of MnNP as a potential matrix for biomolecule immobilization, which can be further extended to immobilize other biocatalysts used in agro-industrial and lab-based applications.