Application of High-pressure Carbon Dioxide in Japanese Anchovy Waste Recycling by Enzymatic Hydrolysis

Anchovy waste, a protein resource with high nutritional value and potential for recycling with a relatively high economic effect, is essential for the Sustainable Development Goals of the United Nations. Preventing microbial contamination during the recycling process, through enzymatic hydrolysis, ensures the safety of recycled products. High-pressure carbon dioxide is a novel non-thermal decontamination technology, which inactivates cells by breaking their membranes. Here, we selected 40 °C_5.0 MPa and 50 °C_1.0 MPa treatment conditions for effectively decontaminating anchovy samples during the hydrolysis process. Next Generation Sequencing and real-time PCR experiments showed that a microbial growth promotion stage existed at the beginning of 40 °C_5.0 MPa, which may threaten hydrolysates, as some microbial genera were detected from the metabolites produced. Treatment at 50 °C_1.0 MPa ensured a high safety level for hydrolysates but this is limiting for various enzymatic hydrolysis processes. Orientaaze OP was selected as an additional enzyme with the highest hydrolysis efficiency under 40 and 50 °C among 10 different industrial proteases. Compared with control samples without high-pressure carbon dioxide treatment, 40 °C_5.0 MPa and 50 °C_1.0 MPa treated samples presented higher total amino acid concentrations by ultra-high-performance liquid chromatography. Hence, there was an increased enzyme activity by 40 °C_5.0 MPa and 50 °C_1.0 MPa treatments in endogenous or additional proteases hydrolytic processes. Despite the need for more future studies to be conducted, this research still provides essential information and instruction for industrial enzymatic hydrolysis applications on anchovy waste recycling.