The grime fighting potential of fish guts and the battle for responsible consumption

Abstract

We live in a world that is dominated by mixed capitalist economies, a continuum of market and government control (Jahan & Mahmud, 2022). Yet, at the heart of any capitalist system is the dependency on consumption to drive economic growth, which is problematic when resources are finite and integral to ecosystems. Consumption also generates waste. Escalating consumption observed throughout the 20^th Century can be found at the root of many environmental catastrophes. Aquatic systems and fish are on that front line, suffering from consumption (e.g. overfishing (Barausse et al., 2011), deforestation (Bojsen & Barriga, 2002) and over abstraction of water (Benejam et al., 2010)) and the end products of consumption (e.g. climate change (Kutsyn, 2025), plastic pollution (Rochman et al., 2013), soil pollution (Stauffer et al., 2011), air pollution (Nduka et al., 2022) and water pollution (Carney Almroth et al., 2021).

To try and save natural systems from the ravages of overconsumption and to protect the natural world in which capitalist systems depend, the United Nations created Sustainable Development Goal 12: Responsible consumption and production (UN, 2024). To achieve the targets within this goal, a post-capitalism vision and roadmap has been proposed by some, whereby the tenets of neoliberalism (free-market capitalism, deregulation, and reduction in government) are replaced with sustainable consumption and reduced waste (Dermody et al., 2021). One approach to reducing waste is through the idea of a circular economy, where materials never become waste.

However, turning waste materials into useful products that can re-enter society takes innovation and can be susceptible to greenwashing. One industry guilty of producing vast quantities of waste are food fisheries, which are geared towards harvesting fillets for human consumption, leaving up to 70% of the fish behind as a by-product (e.g. heads, viscera, skin, bones and scales) (FAO, 2022). At best, that 70% will end up in fishmeal for aquaculture, but more often will end up in landfill, open-air dumps or water sources. This is despite these tissues containing valuable nutrients, minerals, and, as explored by Friedman et al. (2025), enzymes - specifically proteinases found in the intestine.

Proteinases are the most widely used enzymes in industrial bioprocesses, and in previous work Friedman et al. (2022) characterized the optimal pH and temperature for these proteinases, isolated from the guts of four fish species. However, for these enzymes to be used in products such as detergents they must be able to function in the presence of other compounds such as surfactants and oxidizing agents. In this issue, Friedman et al. (2025) build on their previous research and show that the digestive activity of alkaline proteinases from fish guts actually increases when in the presence of commercial detergents when compared to other organic solvents. These are promising results which could pave the way for more environmentally friendly sources of alkaline proteinases, not only for detergents, but for other applications such as in food and beverage production. While there is big leap from research to industry-scale adoption, this work takes us one step closer to the utopia of zero waste and a truly circular economy, securing a future for people and the ecosystems on which we depend.