## 3 Results and Discussion  
### Kinetic Parameters of Fermentation  
The compositional analysis showed that the un-pretreated OPEFB used in this study contained 39.0% cellulose, 29.8% hemicellulose, 22.8% lignin and 1.7% ash, according to [PERSON] et al. [24]. After being alkaline-pretreated, there were significant changes to the composition of the OPEFB, as can be seen in Table 3. The pretreated OPEFB contained 63.97% cellulose, 10.58% hemicellulose, 19.39% lignin and 1.51% ash. This result proved that the delignification of the OPEFB occurred during the pretreatment process. In general, alkaline pretreatment of biomass at elevated temperatures will dissolve hemicellulose and lignin effectively, as the degradation of hemicellulose occurs much \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline Year of analysis & 2020 \\ Construction period & 30 months \\ Start-up period & 4 months \\ Project lifetime & 15 years \\ Interest rate & 7.0\% \\ OPEFB capacity & 2000 kg/batch \\ Labour wage & $0.92/h \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Assigned terms for hand sanitiser plant’s economic evaluation. Figure 2: Complete process flow diagram of hand sanitiser production from OPEFB-based bioethanol in SuperPro Designer® v9.0. faster than that of cellulose [38]. This phenomenon can be seen from the decreasing amounts of both hemicellulose and lignin, but not of cellulose, in the pretreated OPEFB. The high cellulose content in the pretreated OPEFB would be very beneficial for the hydrolysis reaction to produce glucose during SSF. The effect of the fermentation time on the cell concentration at various fermentation temperatures can be seen in Figure 3b. Based on Figure 3b, cell concentration tends to increase with longer SSF times. This shows that the process of cell formation is still at an exponential stage because of the availability of sufficient substrate during the reaction and of reaction conditions that support the process of cell growth. Cell growth phenomena such as the lag phase, stationary phase and death phase have not been seen in the SSF process; this could be due to the large range of times for sampling processes. The lag phase in the cell formation can be predicted at _t_\(\leq\) 24 h. The exponential phase can be seen according to Figure 3b from the 24 th h to the 72 nd h, and after the 72 nd h, cell growth looks constant or enters the stationary phase. On the other hand, the death phase was not seen in this study. This could be due to the abundant amount of substrate, which is indicated by the large residue of OPEFBs at the end of the SSF reaction (_t_ = 96 h). The death phase was also not seen in a study conducted by [PERSON] et al. in which it was stated that the death phase is not seen in the cell growth phase because the substrate is still available for microorganisms to carry out metabolic processes [39]. The effect of temperature on cell growth shows that the higher temperature of SSF produced higher microbial concentrations. This may have been due to the substrate that was used in this process. Figure 3: The concentration of bioethanol (**a**), yeast cell (**b**) and glucose (**c**) during SSF. \begin{table}
\begin{tabular}{c c} \hline
**Parameters** & **Composition (\%)** \\ \hline Ash & 1.51 \\ Lignin & 19.39 \\ Cellulose & 63.97 \\ Hemicellulose & 10.58 \\ \hline \end{tabular}
\end{table} 
Table 3: Composition of OPEFB after NaOH pretreatment. The substrate used in this research was OPEFB, which must be broken down into glucose using the cellulase enzyme. The enzymatic hydrolysis process was generally carried out at a temperature of 50 \({}^{\circ}\)C (\(T\geq\) 30 \({}^{\circ}\)C). At 32 \({}^{\circ}\)C and 35 \({}^{\circ}\)C, the SSF process can cause the enzymatic hydrolysis of OPEFBs to be more effective and to produce more glucose than is produced at lower temperatures (30 \({}^{\circ}\)C). Glucose is used by yeast for cell growth.