Solubilization of meat & bone meal protein by dilute acid hydrolysis for the production of bio-based flocculant

Flocculants are substances that cause suspended particles to aggregate, therefore accelerating sedimentation to produce a clarified solution. They find use in a huge variety of applications including wastewater treatment, erosion control, and paper manufacture. Meat and bone meal (MBM) is a high protein by-product of meat processing. Protein extracted from MBM has been shown to have good flocculation activity, but this protein has poor solubility. Previous attempts to improve solubility through alkaline or enzymatic hydrolysis have produced small protein fragments with low flocculation activity. The objective of this project was to produce large, soluble MBM protein fragments by applying reaction conditions that are known to hydrolyze peptide bonds only at aspartic acid and asparagine residues. In this project, milled MBM was suspended in 0.03N hydrogen chloride solution, under vacuum, and incubated at 108 °C. Samples were removed after 1, 2, and 4 h, and the soluble and insoluble material was separated. The molar mass distribution of soluble material was examined by size exclusion chromatography (SEC), progressive solubilization of protein was measured by using a test for organic nitrogen, and flocculation activity was tested by measuring kaolin clarification effectiveness (KCE). Results showed that at all hydrolysis times, concentration of solubilized material was increased approximately 3-fold compared to the acid-free controls. Results also showed that as reaction duration increased, more MBM protein was solubilized, but average molecular weight (MW) of solute was reduced, and flocculation activity was dependent on reaction duration. The dilute acid hydrolysis (DAH) employed in this project could be a simple and inexpensive treatment that has potential to add value to MBM and provide a new source for bio-based flocculants.