# Production of Cellulosic Ethanol from Enzymatically Hydrolysed Wheat Straws
## 4 Conclusions  
Our results highlighted a highest degradation of lignocellulosic material in the case of pretreatment with 3% (_v/v_) H\({}_{2}\)SO\({}_{4}\) compared to other concentrations of the same acid. This pretreatment led to an increasing of phenolics and organic acids content, especially of protocatechuic (34.72 \(\pm\) 0.06 ug/g), vanillic (18.92 \(\pm\) 0.02 ug/g) and 4-hydroxybenzoic (18.74 \(\pm\) 0.01 ug/g), while the value of acid gluconic was 22.59 \(\pm\) 0.05 mg/g, formic acid was 2.69 \(\pm\) 0.02 mg/g and acetic acid was 0.94 \(\pm\) 0.01 mg/g. The SEM microstructure of the pretreated samples revealed the changes which occurred on the surface of the straws undergoing pretreatment. Significant results were obtained in the case of treatment with 3% (_v/v_) H\({}_{2}\)SO\({}_{4}\). ATR-FTIR analysis showed reduction in the intensity of the peaks characteristic to cellulose, hemicellulose and lignin at increased enzyme doses and S/L ratios, thus confirming the efficiency of the pretreatment and the enzymatic hydrolysis. This study showed that the pretreatment with 3% (_v/v_) H\({}_{2}\)SO\({}_{4}\), in a S/L ratio of 1/30 (_v/v_) and with a dose of enzyme of 90/90 uL/g wheat straw led to the highest concentrations of carbohydrates (xylose 14.31 \(\pm\) 0.11 mg/g, fructose 5.94 \(\pm\) 0.13 mg/g, glucose 84.75 \(\pm\) 0.23 mg/g and total carbohydrates 105.01 mg/g) and as a result the highest ethanol yield after the fermentation process. The yield of ethanol (47.61 \(\pm\) 2.3 g/Kg WS) could be improved if the concentration of H\({}_{2}\)SO\({}_{4}\) (_v/v_) is increased in the pretreatment step, which would probably lead to a more significant disruption of the complex structure of the WS, hence facilitating the action of enzyme mixtures. **Supplementary Materials:** The following are available online at [[http://www.mdpi.com/2076-3417/10/21/7638/s1](http://www.mdpi.com/2076-3417/10/21/7638/s1)]([http://www.mdpi.com/2076-3417/10/21/7638/s1](http://www.mdpi.com/2076-3417/10/21/7638/s1)), Figure S1. HPLC--DAD chromatogram at 280 nm (A) and 320 nm (B) for standard (100 mg/l) for gallic acid--peak 1 (8.69 min), protocatechuic acid--peak 2 (15.953 min), 4-hydroxybenzoic acid--peak 3 (20.886 min), vanillic acid--peak 5 (25.631 min), caffe acid--peak 4 (23.277 min), chlorogenic acid--peak 6 (25.831 min), p-comamic acid--peak 7 (32.011 min), royanamic acid--peak 8 (39.69 min), myriectin--peak 9 (43.216 min), luteolin--peak 10 (49.737 min), quercetin--peak 11 (50.128 min) and kenoriori--peak 12 (56.52 min) and (C--D) content of individual phenolic compounds in acid-pretreated wheat straw (liquid fraction), Figure S2. HPLC-RID chromatogram for standard carbohydrates mix (CAR10-KIT) (A) and hydrolysed WS, D \(-\) (\(-\)) - Ribose--peak 1 (3.738 min), D \(-\) (\(+\)) - Xylose--peak 2 (4.235 min), D \(-\) (\(-\)) - Arabinese--peak 3 (4.771 min), D \(-\) (\(-\)) - Fructose--peak 4 (5.298 min), D \(-\) (\(+\)) - Manrose--peak 5 (5.921 min), D \(-\) (\(+\)) - Glucose--peak 6 (6.273 min), D \(-\) (\(+\)) - Galactose--peak 7 (6.77 min), Sucrose--peak 8 (9.868 min), D \(-\) (\(+\)) - Maltose--peak 9 (12.155 min), \(\alpha\)-Lactose monohydrate--peak 10 (14.302 min) and (B) the carbohydrates content of enzymatically hydrolysed WS, Table S1. Box-Behnken design with coded values. Figure 7: Evolution of CO\({}_{2}\), O\({}_{2}\) and ethanol concentrations during the saccharification and fermentation (SSF) process of WS mash. **Author Contributions:** Conceptualization, V.-F.U. ; formal analysis, V.-F.U. ; funding acquisition, G.G. ; investigation, V.-F.U. ; methodology, V.-F.U. and G.G. ; project administration, G.G. ; software, V.-F.U. ; supervision, G.G. ; validation, G.G. ; writing--original draft, V.-F.U. ; writing--review and editing, V.-F.U. and G.G. All authors have read and agreed to the published version of the manuscript. **Funding:** This work was supported by contract no.