Beauveria bassiana Lipase A expressed in Komagataella (Pichia) pastoris with potential for biodiesel catalysis.

Lipases (EC 3.1.1.3) comprise a biotechnologically important group of enzymes because they are able to catalyze both hydrolysis and synthesis reactions, depending on the amount of water in the system. One of the most interesting applications of lipase is in the biofuel industry for biodiesel production by oil and ethanol (or methanol) transesterification. Entomopathogenic fungi, which are potential source of lipases, are still poorly explored in biotechnological processes. The present work reports the heterologous expression and biochemical characterization of a novel Beauveria bassiana lipase with potential for biodiesel production. The His-tagged B. bassiana lipase A (BbLA) was produced in Komagataella pastoris in buffered methanol medium (BMM) induced with 1% methanol at 30°C. Purified BbLA was activated with 0.05% Triton X-100 and presented optimum activity at pH 6.0 and 50°C. N-glycosylation of the recombinant BbLA accounts for 31.5% of its molecular weight. Circular dichroism and molecular modeling confirmed a structure composed of α-helix and ß-sheet, similar to α/ß hydrolases. Immobilized BbLA was able to promote transesterification reactions in fish oil, demonstrating potential for biodiesel production. BbLA was successfully produced in K. pastoris and shows potential use for biodiesel production by the ethanolysis reaction.

Endo-xylanase GH11 activation by the fungal metabolite eugenitin.

Eugenitin, a chromone derivative and a metabolite of the endophyte Mycoleptodiscus indicus, at 5 mM activated a recombinant GH11 endo-xylanase by 40 %. The in silico prediction of ligand-binding sites on the three-dimensional structure of the endo-xylanase revealed that eugenitin interacts mainly by a hydrogen bond with a serine residue and a stacking interaction of the heterocyclic aromatic ring system with a tryptophan residue. Eugenitin improved the GH11 endo-xylanase activity on different substrates, modified the optimal pH and temperature activities and slightly affected the kinetic parameters of the enzyme.

Functional characterization and oligomerization of a recombinant xyloglucan-specific endo-ß-1,4-glucanase (GH12) from Aspergillus niveus.

Xyloglucan is a major structural polysaccharide of the primary (growing) cell wall of higher plants. It consists of a cellulosic backbone (beta-1,4-linked glucosyl residues) that is frequently substituted with side chains. This report describes Aspergillus nidulans strain A773 recombinant secretion of a dimeric xyloglucan-specific endo-ß-1,4-glucanohydrolase (XegA) cloned from Aspergillus niveus. The ORF of the A. niveus xegA gene is comprised of 714 nucleotides, and encodes a 238 amino acid protein with a calculated molecular weight of 23.5kDa and isoelectric point of 4.38. The optimal pH and temperature were 6.0 and 60°C, respectively. XegA generated a xyloglucan-oligosaccharides (XGOs) pattern similar to that observed for cellulases from family GH12, i.e., demonstrating that its mode of action includes hydrolysis of the glycosidic linkages between glucosyl residues that are not branched with xylose. In contrast to commercial lichenase, mixed linkage beta-glucan (lichenan) was not digested by XegA, indicating that the enzyme did not cleave glucan ß-1,3 or ß-1,6 bonds. The far-UV CD spectrum of the purified enzyme indicated a protein rich in ß-sheet structures as expected for GH12 xyloglucanases. Thermal unfolding studies displayed two transitions with mid-point temperatures of 51.3°C and 81.3°C respectively, and dynamic light scattering studies indicated that the first transition involves a change in oligomeric state from a dimeric to a monomeric form. Since the enzyme is a predominantly a monomer at 60°C, the enzymatic assays demonstrated that XegA is more active in its monomeric state.