Chemical-free recovery of protein from cow manure digestate solid and antioxidant activity of recovered protein

Abstract

Livestock manure solids have a significant content of protein which is not only underutilized, but prone to runoff and eventual breakdown to reactive nitrogen compounds, contributing to eutrophication. We have developed a novel subcritical water extraction process to extract protein from livestock manure solid without the use of any chemical. We demonstrate the versatility of our new process to control the molecular weight distribution of the extracted protein hydrolysate. The antioxidant activity of protein hydrolysate has been examined through Oxygen Radical Absorbance Capacity Assay. The results have shown that our protein hydrolysate had its antioxidant capacity against the peroxyl radical similar to that of vitamin E and exhibited almost 7 times as strong inhibition against the hydroxyl radical as vitamin E. We also evaluated the nutritional value of our PH by analyzing its amino acid composition and the MW distribution through amino acid analysis, SDS-PAGE, and MALDI-TOF mass spectroscopy.