Optimization of protein extraction from bamboo shoots and processing wastes using deep eutectic solvents in a biorefinery approach

Bamboo shoots are a popular food in Asia and throughout the world. As only the tip of the bamboo shoot is edible, significant quantities of processing byproducts are generated, with potential for valorization of these wastes. Deep eutectic solvents (DESs) are emerging as eco-friendly solvents for the extraction of bioactive compounds from natural products. This work investigated the extraction of protein from the tip of the bamboo shoot (TBS), as well as its processing byproducts (basal bamboo shoot (BBS) and sheath) using a DES comprised of compounds accepted as food additives: choline chloride (ChCl) as hydrogen bond acceptor (HBA) and levulinic acid as hydrogen bond donor (HBD). Central composite design (CCD) and Response Surface Methodology (RSM) were used to predict optimum extraction parameters for all bamboo shoot parts with HBA-to-HBD molar ratio of 6, temperature of 80 °C, time of 50 min, water content of 40% (v/v), and solid-to-liquid ratio of 30 mg/mL for TBS, 70 mg/mL for BBS and sheath. Under the optimal conditions, the protein extraction yields were 39.16 ± 1.22 mg/g dry weight (DW) for TBS, 15.46 ± 0.30 mg/g DW for BBS, and 9.54 ± 0.17 mg/g DW for sheath. Compared with conventional extraction using sodium hydroxide (NaOH) solution, significantly higher protein yield was recovered with DES for TBS, and comparable yields obtained for BBS and sheath. Results show the potential of this DES as a carrier for extracted bamboo proteins in functional food applications, as a biorefinery approach for bamboo shoot processing.