# Quantitative analysis of amino acid excretion and consumption by Methanothermobacter marburgensis in fed-batch cultivation mode

## TL;DR

This study explores how Methanothermobacter marburgensis excretes amino acids under different conditions, showing potential for sustainable amino acid production without organic carbon.

## Contribution

The study reveals M. marburgensis's ability to excrete multiple amino acids without organic carbon input, a novel trait for archaea in bioprocessing.

## Key findings

- M. marburgensis excretes a wide range of amino acids influenced by nitrogen availability.
- High ammonium suppresses amino acid excretion, while limited ammonium triggers alanine accumulation and re-assimilation.
- Carbon limitation and nitrogen excess lead to asparagine production, indicating potential for archaea in amino acid bioprocessing.

## Abstract

The methanogenic archaeon Methanothermobacter marburgensis offers a promising alternative to traditional bacterial systems for the sustainable production of proteinogenic amino acids (AAs), eliminating the need for sugar-based feedstock. In this study, we quantitatively examined AA excretion and consumption in fed-batch cultivation mode in bioreactors under varying ammonium (NH4+) concentrations and gas compositions. M. marburgensis demonstrated excretion of a wide spectrum of AAs with distinct profiles shaped by nitrogen availability. While high NH4+ concentrations suppressed total AA excretion, NH4+ limited conditions triggered alanine accumulation followed by its re-assimilation, suggesting a regulatory mechanism linked to nitrogen stress. Moreover, carbon limitation and nitrogen excess resulted in the production of an AA pattern including asparagine. Despite lower overall productivity compared to engineered bacterial strains, M. marburgensis exhibited the unique ability to simultaneously excrete multiple AAs without requiring organic carbon input. These findings advance the feasibility of using methanogens for AA bioprocessing and the development of archaea as next-generation microbial cell factories.

The online version contains supplementary material available at 10.1007/s00726-026-03498-1.