# Production of Cellulosic Ethanol from Enzymatically Hydrolysed Wheat Straws
## 3 Results and Discussions
### Fermentation Process  
[PERSON] et al. (2010) using a similar equipment of BlueSens sensors reported that after pretreatment with 2% NaOH of the raw material and applying the SSF process, after 48 h a maximum concentration of 1.5% ethanol was obtained in the case of corn ostriches, while for wheat straw the highest concentration of bioethanol was 1.33%. The enzymes used in the study were Trichoderma cellulases Onozuka (15 units/g cellulose), Aspergillus cellulases (15 units/g cellulose), Aspergillus cellulose Novo (90 units/g cellulose) and the yeast strain was _Saccharomyces cerevisiae CMIT2_. [75]. [PERSON] and [PERSON] (2006) obtained 15.1 mg/g ethanol following the fermentation process after enzymatic hydrolysis and alkaline pretreatment combined with H\({}_{2}\)O\({}_{2}\)[76].  
[PERSON] et al. (2019) used a combined treatment (microwave-assisted and 0.5% NaOH), 5 FPU/g commercial cellulase (SIGMA) + 5 FPU/g of in-house enzyme (_Aspergillus niger ADH 11_) and followed by SSF with _Saccharomyces cerevisiae 357_. After 34.42 h a maximum ethanol concentration and productivity of 32.44 g/L (0.95 g/L/h) was obtained from WS with a yield of 0.30 g ethanol/g reducing sugar consumed [77].  
[PERSON] et al. (2015) pretreated the wheat straw by steam explosion at 200 \({}^{\circ}\)C, 15 bar for 10 min, with a water to wheat straw ratio of 1, added 30 FPU/g (T. reesei SVG17) and followed by SHCF at 30 \({}^{\circ}\)C, pH 4.5 with S. cerevisiae IBB10B05. The ethanol obtained was 71.2 g/kg WS [78].  
[PERSON] et al. (2014) applied a pretreatment with dilute acid (2.5% (_w/w_) H\({}_{2}\)SO\({}_{4}\)) on WS, 20 FPU/g Sacchar-SEB-C6 (advanced enzyme) + 20 FPU/g of in-house cellulase (_Penicillium janthinellum_) and followed by SSF with _K. marxianus_ MTCC 4136 at 40 \({}^{\circ}\)C. After 48 h of fermentation resulted 12 g/L ethanol [79].  
Xu et.al. (2011) pretreated with the ratio of WS to liquid at 80 g/kg, the NaOH concentration of 10 kg/m\({}^{3}\), the microwave power of 1000 W for 15 min, prehydrolysis at 50 \({}^{\circ}\)C for 24 h with Cellubrix(r) L, pH = 4.8, followed by SSF with _Sacchromyces cerevisiae_ at 32 \({}^{\circ}\)C. After 120 h, the ethanol yield was 148.93 g/kg WS compared to the untreated material which was only 26.78 g/kg [80].  
In this study, the activity of yeast _Saccharomyces cerevisiae_ (DistillaMax SR) was not inhibited by the presence of acetic acid, as it was not identified after enzymatic hydrolysis in the analysed samples.  
After inoculation of the slurry with the yeast _Saccharomyces cerevisiae_ (DistillaMax SR) it can be seen based on the graph generated by the BACVis software that the fermentation process has started. The maximum fermentation was recorded approximately 12-13 h after the inoculation of the yeast, where the highest consumption of O\({}_{2}\) (from 22% vol. initially to approx. 15.1% vol.) and carbohydrates and the releasing of CO\({}_{2}\) (approx. 26.3% vol.), and the bioethanol content was approx. 0.853% vol. After 12-13 h from the maximum of the fermentation process, it can be observed that toward the end of the fermentation, the concentration of ethyl alcohol increased by approximately 0.4% vol. The maximum concentration of bioethanol obtained in gaseous phase from the fermentation process under the conditions presented was 1.20% (_v/v_) (Figure 7), which means the yield of bioethanol was 47.61 \(\pm\) 2.3 g/Kg WS.