Enhance the Growth of Clostridium ljungdahlii Microbial Cells by Modifying the Medium Composition and Trace Metals

Syngas fermentation is an alternative route that combines the advantages of thermochemical and biochemical processes have been proposed for biomass conversion to ethanol. One of the main obstacles to syngas fermentation is the low yield of ethanol, caused by the limited utilization of the syngas substrate due to low microbial cell concentration in the fermentation system. This research examined the modification of fermentation medium to improve microbial cell growth. The modifications were to increase the concentration of micronutrients/trace metals and macronutrients in the medium. The results showed that the maximum mass cell and maximum growth rate produced by microbial growth in the modified trace metal medium were 0.63 g/L and 0.0076 h-1, while in a modified macronutrient medium were 0.97 g/L and 0.0298 h-1. Modification of the macronutrient medium was able to increase the yield of biomass, but the opposite occurred in the modification of the trace metals. Meanwhile, the maximum concentration of ethanol from syngas fermentation in the modified macronutrient medium was lower than the concentration of ethanol in the standard medium.