The effect of syngas composition on the growth and product formation of Butyribacterium methylotrophicum

A carbon monoxide-adapted strain of Butyribacterium methylotrophicum was grown submerged on different head space gas mixtures of carbon monoxide, hydrogen and carbon dioxide. Carbon monoxide was utilized by the B. methylotrophicum strain with acetic and butyric acid as main products. Supplemental carbon dioxide increased initial growth rate and increased product formation especially acetic acid production. Acetic acid was produced in concentrations between 0.6 and 1.3 g/l. Butyric acid, lactic acid and ethanol were produced in lesser concentrations. The total carbon yield to products was between 90% and 110%. Carbon monoxide was almost completely utilized before hydrogen utilization started. Supplemental hydrogen increased the formation of butyric acid and made it possible to convert also carbon dioxide to organic products. Separation of growth and product formation may offer interesting process design options.