From Microorganisms to Biosignatures: Subcritical Water Extraction as a Sample Preparation Technique for Future Life Detection Missions

Abstract

Amino acids are important targets in the search for life beyond Earth. The types of amino acids, their relative abundances, and enantiomeric excess all serve as biosignatures. To detect such biosignatures, identification and quantification of individual amino acids are required. Regardless of the analytical workflow used, it is critical to release amino acids from the sample without altering their molecular distributions. Subcritical water extraction (SCWE) is a promising technique for the release of organics from a variety of samples that has been under development for flight implementation for over 20 years. However, there is a risk of racemization and/or degradation of amino acids during extraction that could alter their distributions. This work demonstrates for the first time that SCWE (200°C for 30 min) can release amino acids from bacterial cells and spores, while maintaining their native distributions and enantiomeric excess.