# Cellulose Recovery from Agri-Food Residues by Effective Cavitational Treatments
## 3 Biomass Treatments for Cellulose Recovery
### Acoustic Cavitation (AC) as Effective Biomass Pretreatment
The authors also investigated the effect of [Bmim]Cl load (0.25-1.50 g) in the same pretreatment process; the sugar yield increased with the increase of SCB load and reached the maximum value (168 mg/g) at 1.25 g of [Bmim]Cl after 72 h. The [Bmim]Cl + PEG-8000 pretreatment has been investigated at the same conditions of IL pretreatment alone with the addiction of different surfactant loadings (10-100 mg) and the maximum sugar yield has been reached with 75 mg of PEG-8000. Finally, the combined US, IL and surfactant pretreatment have been performed mixing 1 g of SCB in 19 mL of 50 mM acetate buffer (pH 5.0). The suspension has been sonicated for 60 min (20 kHz, 100 W, pulsing cycle of 59 s off/59 s on) exploiting a titanium probe tip and then pretreated with 5.0 g of [Bmim]Cl and 300 mg of PEG-8000 at 90 \({}^{\circ}\)C for 2 h. The maximum sugar yield obtained through enzymatic saccharification of US, IL, surfactant pretreated SCB was 255 mg/g biomass, while it was 177 mg/g biomass for US alone and 192 mg/g biomass for the [Bmim]Cl + PEG-8000 pretreatment. Thus, according to [PERSON] et al., the use of surfactant coupled to US and ILs improves the delignification process by increasing the SCB surface area with consequential improvement of mass transfer. Alongside the ionic liquids commonly utilized for biomass pretreatment, an ever-greater interest in natural ILs has recently grown. Completely bioderived ILs such as choline acetate (ChOAc) have been tested in lignocellulosic fractionations as new suitable alternative solvents (biodegradable and bioreenwable) to even more expensive imidazolium ones. In this context, [PERSON] et al. (2013) [101] exhibited that the UAT of a powdered bamboo waste in presence of bioderived ChOAc could significantly enhanceits cellulose recovery and its subsequent saccharification performance. When thermally pretreated (110 \({}^{\circ}\)C) for 60 min in ChOAc, saccharification yields of bamboo powder was around 55%. Conversely, 92% of cellulose was hydrolysed to Glu after UAT (24 kHz and 35 W power) of bamboo powder at 25 \({}^{\circ}\)C for 60 min in the same bioderived IL. Furthermore, the crystallinity of cellulose achievable from the matrix was lower in the case of cavitational process than in case of thermal pretreatment in presence of ChOAc. To deeply explore the pretreatment potential of ChOAc for lignocellulosic substrate, [PERSON] et al. (2015) exploited the cellulosic fraction recovered from the ChOAc UAT of bagasse [102] for subsequent EH. The biomass/IL mixture was sonicated at 24 kHz (35 W power) for 60 min, by using an immersion horn. Saccharification efficiency was evaluated as the percentage of native cellulose in the bagasse hydrolysed into Glu. Likewise, saccharification of hemicellulose was evaluated considering the native percentage of hemicellulose hydrolysed into Xyl. After ChOAc pretreatment, cellulose and hemicellulose saccharifications increased, reaching a maximum of 85% and 100% respectively, after 48 h.  
Furthermore, the application of ILs for in situ enzymatic saccharification of cellulose was investigated. For this purpose, the solubility of cellulose and the subsequent cellulase activity on it were tested by [PERSON] et al. (2010) [103] using different alkylphosphate ILs. Moreover, an UAT was exploited to simultaneously enhance the cellulose conversion. Among the screened solvents, the 1-methyl-3-methylimidazolium dimethylphosphate ([Mmim][DMP]), with favourable solubility and biocompatibility, was selected to establish aqueous-ILs system for enzymatic in situ cellulose saccharification. The conversion of the substrate in aqueous-ILs with US irradiation has an increase of 53% if compared to that recorded for untreated cellulose. Moreover, higher conversions (95%) were documented in aqueous-[Mmim][DMP] by performing a cavitational treatment at 60 \({}^{\circ}\)C (45 kHz, 100 W) for 30 min.