Potential utilization of fish waste for the sustainable production of microalgae rich in renewable protein and phycocyanin-Arthrospira platensis/Spirulina

The fish processing industry generates the solid biological waste (head, trimmings, skin, viscera, scale, bone etc) based on the processing methods, which poses a serious effect on the environment. Fish waste is valorized by various treatment methods which are costly and generate the effluents with high organic load. The objective of the present study was to utilize the fish waste in the form of fish protein hydrolysate (FPH) as an organic nitrogen source for the cultivation of Spirulina instead of inorganic nitrogen. Since the inorganic nitrogen in the algal cultivation accounts for high costs and energy, in addition to the continuous discharge of unspent inorganic nitrogen causing severe environmental problems. The proposed organic nutrient could be a sustainable and environment friendly solution from both the perspective of fish waste valorization and Spirulina cultivation. The proximate and amino acid composition of FPH derived from fish waste were characterized. Inorganic nitrogen (sodium nitrate) in the conventional medium was replaced with different concentrations of FPH varying from 0.1 to 1% (v/v). The effect of various concentrations of FPH on the growth, biomass productivity, biochemical composition and pigments of Spirulina were investigated. FPH concentration of 0.5% enhanced dry cell weight (DCW), biomass productivity (Pb), protein, and phycocyanin content by 34%, 39% and 15% and 98% respectively, compared to the conventional Zarrouk medium (control). Increase in the FPH concentration decreased the in vitro digestibility of the protein. The carbohydrate content and theoretical ethanol production were 5 times higher in the 0.1% FPH concentration than that of control. Results showed that the fish waste in the form of FPH could be a potential organic nitrogen for the cultivation of Spirulina with high quality pigment. Finally, a preliminary sustainability assessment has been made to analyze the bioeconomy of the process. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The fish processing industry generates solid biological waste that has serious environmental impacts. Fish waste can be valorized as fish protein hydrolysate (FPH) for cultivating Spirulina, leading to improved growth, biomass productivity, protein content, and pigment quality. Using fish waste as an organic nitrogen source is a potential sustainable and environmentally friendly solution for both fish waste valorization and Spirulina cultivation.