## 1 Introduction
Enhanced catalytic activity of cellulase with surfactants has been reported for a variety of substrates, including steam exploded spruce, lodgepole pine [27, 30, 31, 32], sigma cell 100 and steam exploded poplar [32], newspaper [33], Avicel and tissue paper [34], dilute sulfuric acid pretreated creeping wild ryegrass [29], Douglas fir exploded with SO2 and ammonia freeze explosion (AFEX) pretreated corn stover, dilute acid pretreated corn stover [26, 35], lime and ammonia recycled percolation (ARP) pretreated corn stover [26], extrusion pretreated corn stover and prairie cord grass [36, 37]. While all amphiphiles share, to some extent, common properties, \"biopolymers\" are favored over synthetic polymers, because the former are naturally produced, biodegradable, available at relatively low cost and do not require harsh chemical treatments to initiate polymerization. Although polyethylene glycol (PEG) or surfactants such as Tween 20 or 80 are generally recognized to be safe and stimulatory to microbes for enhanced enzyme (e.g., a-amylase) production [38] and ethanol production [39], in some cases even small quantities (1 g/L) of Tween 20 were found to be inhibitory to _Dekkera clausenii_[40]. In addition, the high viscosity of surfactants and their foaming property might not be favorable attributes for scale up. As an alternative, protein-based lignin-blockers such as soybean meal, corn steep liquor, bovine serum albumin (BSA), amylase, chicken egg albumin, and combinations thereof [41], as well as casein [37] have been evaluated during enzymatic saccharification of high lignin containing biomass. Pretreatment techniques such as ammonia fiber explosion (AFEX), dilute acid (with Parr reactor), lime, washed SO2 and Ammonia recycled percolation (ARP) pretreated corn stover, Douglas fir pretreated with SO2 explosion and Avicel were used with prior treatment with bovine serum albumin (BSA) [1, 41]. Table 1 summarizes amphiphiles, pretreatment techniques, and levels of enzyme loading that have been investigated to increase activity of cellulolytic enzymes in biomass-to-ethanol processes. \begin{table}
\begin{tabular}{l l c c c c c} \hline \hline \multirow{2}{*}{**Pretreatment**} & \multirow{2}{*}{**Substrate**} & **Additive** & \multicolumn{2}{c}{**Celluales**} & \multirow{2}{*}{**Increase in**} & \multirow{2}{*}{**References**} \\  & & **amount** & & & **dose (FPU/g** & & **Yg (\%)** & \\ \cline{3-6}  & & **(g/g glucan)** & & & **glucan** & & \\ \hline N/A & Avicel & 0.30 & PEG 6000 & 8.6 & 3.0 & [PERSON] _et al._[36] \\  & Avicel & 0.60 & Tween 20 & 7.5 & 64.0 & [PERSON] and [PERSON] [26] \\  & Avicel & 0.30 & Tween 20 & 8.6 & 12.0 & [PERSON] _et al._[37] \\  & Avicel & 0.06 & PEG 4000 & 15.0 & 51.0 & [PERSON] _et al._[27] \\  & Avicel & 0.50 & Casein & 15.0 & 0.0 & [PERSON] _et al._[42] \\ \hline N/A & Newspaper & 0.60 & Tween 20 & 2.0 * & 55.0 & [PERSON] and [PERSON] [40] \\  & Newspaper & 0.60 & Tween 80 & 2.0 * & 42.9 & [PERSON] and [PERSON] [40] \\  & Newspaper & 0.60 & F 68 & 2.0 * & 64.2 & [PERSON] and [PERSON] [40] \\  & Newspaper & 0.60 & F 88 & 2.0 * & 63.7 & [PERSON] and [PERSON] [40] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of the effectiveness of different amphiphiles for improvement of enzymatic hydrolysis of dilute acid, lime, alkali, extrusion, AFEX pretreated substrates.