Microalgae for nutrient recycling from food waste to aquaculture as feed substitute: a promising pathway to eco-friendly development

BACKGROUND: The discharge of food waste and eutrophication in aquaculture could cause environmental pollution and ecological disasters in the hydrosphere. Herein, a novel model of growing microalgae to recover nutrients from food waste and produce feed substitute for aquaculture is proposed. RESULTS: This study developed different methods to pretreat soybean fermentation effluent (SFE) and assessed the contribution of algal growth to nutrient recovery from SFE. Particularly, change of bacterial community was analyzed to explore the interaction between microalgae and bacteria in SFE remediation. In addition, the inclusion level of microalgae in fish diet was optimized and the effect of fresh microalgae on the aquaculture environment was studied. The results showed that unsterilized SFE with appropriate dilution is favorable for microalgal growth and biomass accumulation. Interaction between microalgae and acidogenic bacteria, including Prevotella sp., Acidaminococcus sp. and Lactobacillus sp., favored nutrient recovery from SFE. Removal efficiency of chemical oxygen demand, total nitrogen, total phosphorus and total ammonia-nitrogen in SFE reached 95.66%, 35.35%, 57.70% and 42.21%, respectively. As the optimal inclusion level of microalgae in fish diet was set as 25%, body length and weight of Micropterus salmoides increased by 13.85 mm and 1.73 g in 44-day culture. It was also found that fresh microalgae added in fish diet could effectively keep the ammonia concentration in aquaculture system at a lower level. CONCLUSION: The implementation of this model will be of importance to circular economies integrating food waste remediation and eco-friendly aquaculture. (c) 2021 Society of Chemical Industry (SCI).

Automated summary

This study proposed a novel model of growing microalgae to recover nutrients from food waste for aquaculture feed production. The optimal pretreatment of soybean fermentation effluent and inclusion level of microalgae in fish diet improved microalgal growth, fish growth, and reduced ammonia concentration in aquaculture system, benefiting circular economies.