Thermostable and O2-Insensitive Pyruvate Decarboxylases from Thermoacidophilic Archaea Catalyzing the Production of Acetaldehyde

Abstract

Pyruvate decarboxylase (PDC) is a key enzyme involved in ethanol fermentation, and it catalyzes the decarboxylation of pyruvate to acetaldehyde and CO2. Bifunctional PORs/PDCs that also have additional pyruvate:ferredoxin oxidoreductase (POR) activity are found in hyperthermophiles, and they are mostly oxygen-sensitive and CoA-dependent. Thermostable and oxygen-stable PDC activity is highly desirable for biotechnological applications. The enzymes from the thermoacidophiles Saccharolobus (formerly Sulfolobus) solfataricus (Ss, Topt = 80 °C) and Sulfolobus acidocaldarius (Sa, Topt = 80 °C) were purified and characterized, and their biophysical and biochemical properties were determined comparatively. Both enzymes were shown to be heterodimeric, and their two subunits were determined by SDS-PAGE to be 37 ± 3 kDa and 65 ± 2 kDa, respectively. The purified enzymes from S. solfataricus and S. acidocaldarius showed both PDC and POR activities which were CoA-dependent, and they were thermostable with half-life times of 2.9 ± 1 and 1.1 ± 1 h at 80 °C, respectively. There was no loss of activity in the presence of oxygen. Optimal pH values for their PDC and POR activity were determined to be 7.9 and 8.6, respectively. In conclusion, both thermostable SsPOR/PDC and SaPOR/PDC catalyze the CoA-dependent production of acetaldehyde from pyruvate in the presence of oxygen.

Efficient Mycoprotein Production with Low CO2 Emissions through Metabolic Engineering and Fermentation Optimization of Fusarium venenatum

“…venenatum, which results in the loss of carbon sources, is one of the dominant factors limiting the efficient conversion of glucose. In filamentous fungi, pyruvate decarboxylase, catalyzing the conversion of pyruvate to CO 2 and acetaldehyde, is located upstream of the ethanol synthesis pathway. , Therefore, mining and deleting the major pyruvate decarboxylase gene are expected to improve the carbon conversion ratio of mycoprotein synthesis in F. venenatum by eliminating the byproduct ethanol synthesis and reducing CO 2 emissions.…”

“…In filamentous fungi, pyruvate decarboxylase, catalyzing the conversion of pyruvate to CO 2 and acetaldehyde, is located upstream of the ethanol synthesis pathway. 26,42 Therefore, mining and deleting the major pyruvate decarboxylase gene are expected to improve the carbon conversion ratio of mycoprotein synthesis in F. venenatum by eliminating the byproduct ethanol synthesis and reducing CO 2 emissions. A genome-wide search revealed that six putative pyruvate decarboxylase genes, namely, FvPDC1 (FVRRES_04483), FvPDC2 (FVRRES_05923), FvPDC3 (FVRRES_07836), FvPDC4 (FVRRES_10917), FvPDC5 (FVRRES_12505), and FvPDC6 (FVRRES_12865), were identified in F. venenatum.…”