## 1 Introduction
### Impact of Amphiphiles on Hydrolysis and Fermentation of Biomass  
Studies that applied surfactants or protein-based amphiphiles during enzymatic hydrolysis of lignocellulosic biomass with cellulase and/or xylanase, reported that surfactants can increase sugar yield from lignocellulosic substrates [1,19,26,27,37,38,44,45]. In a typical procedure, pretreated biomass is incubated with nonionic surfactants (0.15 to 0.75 g/g glucan) [26,37,38] in a shaking incubator at temperatures of 50-60 \({}^{\circ}\)C for 1 h [44], or 15 min-4 h [1,26,36] prior to addition of cellulase. This procedure has resulted in a range of sugar yield improvements shown in Table 1. Some authors have tested the impact of amphiphiles on separate or simultaneous saccharification and \begin{table}
\begin{tabular}{l l c c c c c} \hline
**Pretreatment** & **Substrate** & \begin{tabular}{c} **Additive** \\ **amount** \\ **(g/g glucan)** \\ \end{tabular} & **Additive** & \
\begin{tabular}{c} **Cellulose dose** \\ **(FPU/g glucan)** \\ \end{tabular} &
\begin{tabular}{c} **Increase in** \\ **Y\({}_{\pi}\) (\%)** \\ \end{tabular} & **References** \\ \hline AFEX & Corn stover & 0.60 & BSA & 7.5 & 11.6 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.60 & Tween 20 & 7.5 & 10.3 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.60 & PEG 6000 & 7.5 & 6.5 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.50 & Casein & 25.0 & 17.4 & [PERSON] [42] \\  & Corn stover & 2.50 & Casein & 25.0 & 23.7 & [PERSON] [42] \\ \hline Dilute acid & Corn stover & 0.60 & BSA & 3.0 & 26.3 & [PERSON] and [PERSON] [26] \\  & Corn stover & 1.40 & BSA & 15.0 & 12.1 & [PERSON] and [PERSON] [35] \\  & Corn stover & 1.40 & BSA & 7.5 & 12.1 & [PERSON] and [PERSON] [35] \\  & Corn stover & 0.60 & Tween 20 & 3.0 & 36.0 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.60 & PEG & 3.0 & 45.8 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.50 & Casein & 25.0 & 31.9 & [PERSON] [42] \\  & Corn stover & 2.50 & Casein & 25.0 & 31.0 & [PERSON] [42] \\ \hline Lime & Corn stover & 0.60 & Tween 20 & 7.5 & 20.0 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.60 & BSA & 7.5 & 3.0 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.60 & PEG & 7.5 & 0.0 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.50 & Casein & 25.0 & 17.0 & [PERSON] [42] \\  & Corn stover & 2.50 & Casein & 25.0 & 22.3 & [PERSON] [42] \\ \hline Alkali & Corn stover & 0.15 & Triton X-100 & 15.0 & 0.0 & [PERSON] [43] \\  & Corn stover & 0.30 & Brij 30 & 15.0 & 0.0 & [PERSON] [43] \\  & Corn stover & 0.47 & Tween 20 & 15.0 & 0.0 & [PERSON] [43] \\  & Corn stover & 0.50 & Casein & 25.0 & 22.7 & [PERSON] [42] \\  & Corn stover & 2.50 & Casein & 25.0 & 24.8 & [PERSON] [42] \\ \hline Extrusion & Corn stover & 0.47 & Tween 20 & 8.6 & 27.5 & [PERSON] [37] \\  & Corn stover & 0.51 & PEG 6000 & 8.6 & 25.4 & [PERSON] [36] \\  & Corn stover & 0.50 & Casein & 25.0 & 29.5 & [PERSON] [42] \\  & Corn stover & 2.50 & Casein & 25.0 & 38.4 & [PERSON] [42] \\ \hline Raw & Corn stover & 0.15 & BSA & 7.5 & 22.5 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.30 & Tween 20 & 7.5 & 16.7 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.15 & PEG & 7.5 & 22.2 & [PERSON] and [PERSON] [26] \\  & Corn stover & 0.50 & Casein & 25.0 & 14.4 & [PERSON] [42] \\  & Corn stover & 2.50 & Casein & 25.0 & 23.5 & [PERSON] [42] \\ \hline \end{tabular}
* An enzyme level of 2.0 g/L was used in research conducted by [PERSON] and [PERSON]. [40].  
\end{table} 
Table 1: _Cont._ferentation of biomass (SHF and SSF). [PERSON] _et al._[39] reported several positive effects from the application of Tween 20 (2.5 g/L) during SSF of softwood. These benefits included enhanced liquefaction and a 50% reduction in enzyme use, an 8% increase in ethanol yield, and reduced fermentation time. In agreement with these results, [PERSON] _et al._[38] demonstrated that Tween 80 (0.4 g/L) and Zeolite-like products (2.5 g/L) increased ethanol yield significantly during SSF of steam-exploded poplar.