Abstract EANA2025-154

Future lander missions to the icy moons and other celestial bodies in our solar system will likely require the collection and in situ analysis of liquid water samples. In current aquatic environmental bioanalytics, such as marine biology and microbiological water quality monitoring, microbial biomass is commonly concentrated by pumping large volumes of water through membrane filters. However, recovering microorganisms from conventional membrane materials presents a significant challenge due to strong microbial adhesion. Poor recovery often necessitates the use of strong mechanical forces (e.g., vigorous shaking), manual disassembly, or even breakage of the filter housing to retrieve the attached biomass. For future autonomous missions involving the autonomous collection and analysis of terrestrial or extraterrestrial aquatic samples, improved biomass recovery methods are essential to ensure efficient, reliable, and human-free sample handling. Ultrasound vibrations can transmit substantial mechanical forces in liquid media due to various physical phenomena such as cavitation, acoustic radiation pressure and acoustic streaming. Furthermore, in many cases ultrasound treatment increases the flux by preventing fouling of membrane filters.

In this pilot study, we developed and assessed methods for recovering microbial biomass via reverse-flushing—both with and without ultrasound agitation—using various membrane filters (Millipore® 0.22 μm PVDF, Durapore® 0.22 μm PVDF, and Nalgene™ 300–4000), as well as different filter cartridge formats (Sterivex® and custom-made). These techniques are being prepared for implementation in the semi-autonomous modular field laboratory AstroBioLab during the upcoming TRIPLE-LifeDetect expedition to Antarctica, funded by the German Space Agency at DLR (German Aerospace Center). Escherichia coli, Bacillus subtilis, Bacillus atrophaeus, and Saccharomyces cerevisiae served as model organisms. Biomass concentrations (below 10-4 cells per mL) were adjusted and assessed both photometrically (OD600) and by colony-forming unit (CFU) counting to evaluate cell viability before and after recovery. Our first results show that Sterivex® filters can be effectively reverse-flushed, with and without ultrasound, even after 24–48 hours of storage at 4 °C. Most microbial cells were recovered during the first 3-10 milliliters of reverse-flushing, indicating that small volumes (as little as 3 mL) may suffice when flushing pressure is optimized. The addition of ultrasound (1.4 MHz, 1 W) further enhanced recovery in some cases, suggesting its potential for fine-tuning future automated protocols. Further work is necessary to optimize ultrasound parameters—including frequency, intensity, duration, and acoustic field geometry—to maximize detachment efficiency while maintaining cell viability. These findings can contribute to the development of advanced filtration and recovery systems for future autonomous exploration of aquatic environments on Earth and beyond.