A significant amount of insoluble fibrous protein, in the form of feather, hair, scales, skin and others are available as co-products of agro industrial processing. These wastes are rich in keratin and collagen. This study evaluated different fungi for the hydrolysis of insoluble fish protein residues. Proteins resulting from Micropogonias furnieri wastes through pH-shifting process were dried and milled for fermentation for 96 h. This resulted the production of keratinolytic enzymes in the medium. Trichoderma sp. on alkaline substrate (28.99 U mL-1) and Penicillium sp. on acidic substrate (31.20 U mL-1) showed the highest proteolytic activities. Penicillium sp. showed the largest free amino acid solubilization (0.146 mg mL-1) and Fusarium sp. the highest protein solubilization (6.17 mg mL-1).

The objective of this study was to obtain and evaluate physicochemical and functional properties of protein concentrates from Micropogonias furnieri produced by pH shifting process, using alkaline and acid solubilization followed by isoelectric precipitation of muscle proteins. The concentrates showed high protein content and the maxim solubility for the minced (96.5%), for the alkaline (97.5%) and acid (93.7%) extraction was obtained at pH 11.0. The water holding capacity of the alkaline concentrate resulted in a value same or superior to water holding capacity of the acid concentrate in all investigated values of pH. The oil holding capacity of alkaline and acid concentrates showed no significant difference between the studied processes.