Extraction Characterization and Optimization of Protein From Food Waste and Waste-Activated Sludge.

Abstract

Tere is a growing interest in the recovery of valuable biomaterials from waste in line with reaping the benefts of a circular economy. Organic wastes, such as waste-activated sludge (WAS) and food waste (FW), contain a substantial amount of protein that can be recovered for various applications. Tis study compared thermal alkaline and acid hydrolysis methods for their efciencies in extracting protein from FW and WAS. Te possibility of enhancing protein yield and quality through co-extraction of WAS and FW was also investigated. Response surface methodology was used to optimize the extraction process. Before extraction, WAS was purifed by removing heavy metals using acid pretreatment. It was established that FW had 21.5 g/100g protein, while WAS had 19.9 g/100g protein. Te two extraction methods had superior extraction for WAS as compared to FW. In addition to this, there was no signifcant increase in protein yield in the co-extraction of protein from the FW and WAS mixture. Furthermore, optimization using RSM showed that the optimal yield of 15.8 g/100g was obtained at a pH of 13 and a temperature of 120°C, close to the experimental yield of 16.6 g/100g WAS. Moreover, LC–MS analysis of the extracted protein showed that WAS had a good essential amino acid profle with threonine, lysine, leucine, methionine and valine in concentrations of 3.3, 2.7, 1.8, 1.1, and 2.7 g/100g, respectively. Signifcantly, the level of threonine revealed the potential of benefciation of WAS as an animal food supplement because threonine plays an important role in the synthesis of mucosal protein that lines and protects the intestinal tract as well as modulation of nutritional metabolism and macromolecular biosynthesis in animals. In addition to that, the ratio of the frst limiting amino acids (lysine and methionine) met the standards for animal feed supplementation.