Optimisation of operational parameters in laboratory-scale enzymatic protein hydrolysis of fishery waste for biostimulant production

The global fish production sector is crucial for food security, employment, and economic sustainability, with projected growth to 204 million tonnes by 2030. However, significant waste (25-30% of biomass) is produced, leading to environmental concerns and disposal costs. This study explores enzymatic protein hydrolysis (EPH) as a sustainable method for recovering valuable biomolecules from fish and mollusc waste, contributing to a circular economy. Various operational parameters, including temperature, pH, enzyme type, hydrolysis duration, enzyme-tosubstrate ratio, and substrate dilution, were investigated to optimise nitrogen recovery (NR) and crude protein (CP) yield. The results showed that most CP recovery occurred within the first four hours. Alcalase® at 60°C demonstrated enhanced NR compared to Protana Prime®, while pH adjustments had minimal impact, reducing the need for chemical control. A 1:1 substrate-to-water ratio resulted in a similar NR as that of 1:2 with reduced water quantity, and halving the enzyme dosage achieved comparable recovery, leading to cost savings. These findings suggest the potential for scaling up to pilot and industrial levels, with significant savings in energy, water, chemicals, and enzyme use. Future studies should assess biostimulant efficacy and economic feasibility at a larger scale.