Butanol production in mineral medium and hydrolysates were much lower than in medium A, probably due to an
absent of complex nitrogen sources such as yeast extract and peptone that are essential for optimum growth and
solvent production [4] and also due to a low sugar concentration. Our result in medium A also shows the importance
of complex nitrogen sources. Previous report shows that butanol concentrations from the fermentation with initial
sugar of 10 – 20 g/l are 2 – 4 g/l since a low sugar concentration may permits the accumulation of butyrate which
competes with butanol synthesis [9]. These relatively low sugar concentrations in medium B, C, and D are inevitable
due to some restriction in the hydrolysis steps such as the problem in suspending the biomass at a high concentration
before hydrolysis. The butanol yields obtained from the fermentation in medium C and D are close to the theoretical
yield (41 g/100 g glucose). The lower yield in medium B shows that butanol fermentation is not completed.