Bioéthanol (document en anglais)

A specific relationship between the combined level of furfural

and HMF and the rate of ethanol production with Saccharomyces

cerevisiae was identified in a study done by Taherzadeh et al.

(1997). This study supported the same trend outlined in the other

studies mentioned previously by showing the inhibition of the

yeast beyond the furfural and HMF concentration of 1 g/L. An equation

for this relationship was approximated from a diagram in the

publication using Microsoft Excel to generate a 3rd-order polynomial

regression trend line. For the simulation, it was assumed that

the recombinant yeast from Krishnan et al. (1999) would be inhibited

by the combined furfural and HMF to the same degree as the

natural yeast.

Table 5 shows the output of the fermentation simulation with

the approximated ethanol yields, exhibiting the expected relationship

with combined furfural levels. The combined furfural levels

under 10 mg/g (1 g/L) combined with the sugar yields over 90%

give ethanol yields greater than 80%. This confirms that a pretreatment

with 1.2% acid at 140 C for 30 min is an optimal option as

well as 0.9% acid at 160 C for 5 min. The simulation also supports

the use of 1 g/L as the threshold for furfural production when

assessing the data for optimal pretreatment conditions.

3.6. Operating region for optimal pretreatments

The data presented in this study has identified two optimal pretreatment

parameter options. However, if a contour plot for the total

sugar data is overlaid on a contour plot of the furfurals data, we

can find regions containing pretreatment condition combinations

with the potential for high total sugar production and furfural production

around 1 g/L that are not covered experimentally in this

study. Fig. 4 shows four contour plots with total sugar yields represented

by the solid lines and total furfurals generated represented

by the dashed lines. Each plot is at one level of the time

factor. Favorable operating regions in between 10 mg furfurals/g

raw biomass and 400 mg total sugars/g raw biomass can be found

on each plot. These regions do not extend below 0.7% acid, above

165 C, or below 125 C on any of the plots within the range of

the

...