From fish-processing waste to feed additives for crayfish

Abstract

This research studied the in vitro compatibility of Cherax quadricarinatus digestive proteases and crude enzyme extracts recovered from fish-processing waste to evaluate their potential use as feed additives to increase digestion efficiency in decapod crustaceans. The sources of exogenous enzymes were: Pleoticus muelleri (Pm), Artemesia longinaris (Al), and Illex argentinus (Ia). The midgut glands of early (7.2 ± 0.34 g) and advanced juveniles (13.8 ± 1.49 g) of C. quadricarinatus were used for all the assays. The compatibility and synergy between crayfish and exogenous enzymes were evaluated through sodium dodecyl sulfate?polyacrylamide gel electrophoresis (SDS?PAGE) electrophoresis and the hydrolysis of azocasein and four different meals. SDS?PAGE gels demonstrated that crayfish bands remained active when their enzymes were combined with the enzymes from Pm and Ia. An apparent enzymatic synergism was found when Pm and crayfish proteases were incubated together at pH 6 and 8 with azocasein (p ˂ 0.05). The ability to hydrolyze the different feed ingredients varied among the enzyme combinations assayed. Our findings suggest that fish waste has potential as a source of proteases, adding value to these processing residues and promoting a zero-waste industry. Enzymes obtained from Pm and Ia are suitable to be used as food additives for crayfish. The results should be validated through feeding trials.