Fluorescence-based Quantification of Bioactive Keratin Peptides from Feathers for Optimizing Large-scale Anaerobic Fermentation and Purification

Abstract
The extremely thermophilic eubacterium Fervidobacterium islandicum AW-1 produces low molecular weight (LMW; < 1 kDa) keratin peptides (KPs) from poultry feathers at 70°C. However, detection and quantification of feather hydrolysate-derived peptides is needed for optimizing fermentation and down-stream processes. Herein, we developed a large-scale fermentation and purification of skin anti-aging LMW KPs from recalcitrant feathers using fluorescence-based quantification of N-terminal prolinecontaining KPs derivatized with 3,4-dihydroxybenzoic acid to yield fluorescent adducts. Fluorescent products were correlated with bioactive KP concentrations in keratin fractions and cosmetic formulations. Subsequent anaerobic fermentative keratinolysis and large-scale purification achieved 4.4 g/L LMW KPs from 8 g/L native feathers in a 5 L batch bioreactor, generating 0.8 g/L purified MMP- 1 suppressive KPs (yield = 1.2%). This demonstrated the feasibility of industrial-scale anaerobic feather digestion and purification of LMW KPs to produce skin anti-aging peptides from keratin hydrolysates in a more environmentally sustainable manner.