Growth rate dependence of solventogenesis and solvents produced byClostridium beijerinckii

Abstract

Acidogenesis and solventogenesis byClostridium beijerinckii NRRL B-593 has been studied in batch growth, and in sucrose-limited chemostat and recycling fermentor growth. Cells grown in batch culture without pH control primarily produced either butyric and acetic acids, or these acids plus butanol, ethanol and isopropanol in ratios depending on the medium's content of reducing agent, calcium and iron. Cells in chemostat-culture at a mass doubling time (td) of 5.8 h produced primarily butyric and acetic acids at pH 6.8 and these acids plus butanol, ethanol and isopropanol at pH 4.8. Cells grown in a recycling fermentor (in which the td continuously increases) at pH 6.8 entered solventogenesis at a td of 43 h, producing primarily propanol, ethanol and butanol, along with butyric acid, but with greatly decreased production of acetic acid. Although “clostridial form” morphology, succeeded by sporulation, usually accompanied solventogenesis, the association was not invariant so that solventogenesis and sporogenesis can occur separately in this species.