The effect of different experimental conditions on refractive index, Brix value and ethanol production yield were investigated. The values of refractive index, Brix value and ethanol production yield of samples are presented in table 1 (additional data are given in Online Resource 1). For each sample, 10 times sampling was carried out and each sampling were consisted of 25 drop in different times. Then refractive index, Brix value and ethanol production yield were determined. The Brix value is a measure of the amount of sugar in a solution that depends on the refraction of light. One degree of brix is equal to one gram of sucrose per 100 grams of solution. Brix grade represents the percentage by weight of solids in a solution to the total weight of the solution, or in other words, the weight percentage of solids in solution. So the high or low level of brix is affected by the amount of solid in the products [29-30].
Effect of Temperature
Bagasse is in non-powder form in the samples 1 and 2 and fermentation was carried out without acidic or basic hydrolysis conditions at both room and boiling temperature. The obtained bioethanol in 10th series containing 25 drops of each sample at consecutive times after collecting the distillated samples. As shown in table 1, the most amount of ethanol was in the first 25 drops of both samples 1 and 2. Also, comparison of these results shows that in the boiling temperature due to destruction of cellulosic tissue and better releasing of monomers and increasing ethanol production. It seems that, cellulose structure in bagasse due to boiling condition breaks down well, following more sugar released and more alcohol was produced .
Effect of pH
To investigate the effect of pH on the yield of ethanol production, acidic and basic hydrolysis fermentation was performed (samples 3 and 4 in Table 1). Sample 3 shown higher efficiency of fermentation by acid hydrolysis.
Effects of Sample Mode and the Amount of Yeast
In samples 6 to 14 amounts of bagasse and yeast were decreased. The powdered and non-powdered effects of bagasse were examined in ambient and boiling temperature. At the same amounts of water, bagasse and yeast (sample 10 and 13), the powder mode has a greater effect on the fermentation process of ethanol than the non-powdered one. By examining the effect of yeast on samples 3 and 5, it can be seen that the fermentation efficiency is higher in the presence of yeast.
1 µl of synthesized ethanol in the best condition was injected to the GC-MS device (fig. 2). From table 1 it is noted that this information is corresponding to the tube 3 from sample 8 that has the best conditions for the production of ethanol according to Brix and refractive indexes. In this sample with highest amount of ethanol production, four compounds were identified such as ethanol, carbon dioxide, and acetone and benzyl alcohol. As shown in Table 2, the amount of ethanol was 88.38%.