In this present study, the inhibition effect of different concentrations of sugar degradation products in upstream processing (Hydroxymethylfurfural (HMF) and Furfural) and butanol as product inhibition in downstream processing on the growth of Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564) for the production of biobutanol in ABE Fermentation has been investigated. It was found that the presence of HMF and Furfural is non-toxic to cell growth and biobutanol production at concentrations below 3 g/L in the fermentation medium. The specific growth rate for both HMF and furfural was 0.067 h−1 and 0.066 h−1 respectively which is very close to the control medium without any inhibitor addition (0.068 h−1). Surprisingly, the addition of 1 g/L HMF has improved the yield of biobutanol from 0.020 g/g (control) to 0.034 g/g and the addition of 1 g/L Furfural has improved the yield of biobutanol to 0.042 g/g. Butanol inhibition study on the growth of C. saccharoperbutylacetonicum N1-4 (ATCC 13564) shows the decrease of specific growth rate from 0.071 to 0.065 h−1 when 5 g/L butanol was added. 15 g/L of butanol addition has caused a significant drop in the specific growth rate to 0.011 h−1 with an inhibitory effect of 85.7%. This result reveals that sugar degradation product has an inhibitory effect on the growth of microorganisms and biobutanol production at a certain concentration, and this ABE fermentation suffers from product inhibition. Therefore, the development of a robust strain is necessary to make this biobutanol industrially competitive even in the presence of the inhibitory compound.
