Potassium bicarbonate serves as a physiological buffer and potassium source in biochemical applications. Its near-neutral pH and K⁺ compatibility make it particularly useful for plant cell culture, enzyme stabilization, and CO₂-dependent assays.
Chemical Properties
Potassium bicarbonate (KHCO₃, MW 100.12 g/mol) forms white monoclinic crystals (density 2.17 g/cm³) with ionic bonding between K⁺ and resonance-stabilized HCO₃⁻ ions. The bicarbonate ion features a central carbon atom bonded to three oxygen atoms (one protonated, delocalized -1 charge). It is soluble in water (22.4 g/100 mL at 20°C), yielding slightly alkaline solutions (pH 8.2–8.6 for 0.1 M) via the equilibrium:
HCO₃⁻ + H₂O ⇌ H₂CO₃ + OH⁻ (pKa₂ 10.33)
Potassium bicarbonate decomposes above 100°C to K₂CO₃, CO₂, and H₂O.
Biochemical Applications
In cell biology, 10–50 mM KHCO₃ is used in MS media for plant protoplast culture, maintaining pH 7.8 with 2–5% CO₂ and supplying K⁺ for turgor. In enzymology, 25–100 mM stabilizes carbonic anhydrase or PEPCK (pH 8.0–8.5). In molecular biology, it is applied in carbonate washes post-alkaline lysis to neutralize solutions without introducing Na⁺. In winemaking biochemistry, 5–20 mM KHCO₃ buffers malolactic fermentation, converting L-malate to L-lactate.
