# Microgravity-induced constraints on melanin bioproduction: investigating E. coli metabolic responses aboard the international space station

## TL;DR

This study shows that microgravity on the ISS reduces melanin production in E. coli, likely due to metabolic and stress-related changes.

## Contribution

The study provides new insights into how microgravity affects microbial metabolism and bioproduction in space.

## Key findings

- ISS-grown E. coli produced significantly less melanin than ground controls despite functional tyrosinase.
- Microgravity caused elevated extracellular tyrosine and reduced bacterial viability in LSMMG experiments.
- Proteomic and metabolomic analyses revealed oxidative stress and disrupted redox balance in microgravity.

## Abstract

Space biomanufacturing using engineered microbes offers a sustainable approach for producing biomaterials, pharmaceuticals, and essential metabolites, critical for long-duration space missions. However, microgravity-induced physiological changes can alter microbial metabolism and biosynthetic efficiency. This study investigated the effects of microgravity on melanin biosynthesis in non-motile Escherichia coli aboard the International Space Station (ISS). Despite expressing functional tyrosinase, ISS-grown E. coli exhibited significantly lower melanin production than ground controls. Differential pulse voltammetry revealed high extracellular tyrosine in ISS samples, indicating inefficient substrate catalysis. Low Shear Modeled Microgravity (LSMMG) experiments in the Rotating Wall Vessel bioreactor confirmed reduced melanin production and bacterial viability. Proteomic profiling identified increased expression of membrane, transport, and stress-related proteins, while metabolomic analysis showed elevated trehalose and decreased glutathione, indicating oxidative stress and perturbed redox homeostasis. These findings highlight the impact of microgravity on microbial metabolism and provide insights for optimizing microbial biomanufacturing in extraterrestrial environments.