The Future of Astronaut Nutrition: Daily Production of Kefir Nutrient Packs in a Lunar Analog Mission

Astronaut nutrition will need to be supplemented with fresh nutrients and probiotics for long duration space travel. Kefir is a fermented milk beverage that provides probiotic bacteria, protein, calcium, and vitamin K. It has been historically cultured for thousands of years and is a modern-day health food. During the BioNutrients-2 experiment, one generation of kefir was cultured by astronauts on the ISS in fluorinated ethylene propylene (FEP) bags. This follow-on experiment aimed to test the hypothesis that kefir can be produced at ambient temperatures and safely passaged to make a series of nutrient packs in an analog environment. The Hawaiian Space Exploration Analog and Simulation (HI-SEAS) is a semi-controlled habitat located on the Mauna Loa volcano on the island of Hawaii at 2,500 m elevation. The recent EMMIHS (EuroMoonMars, International MoonBase Alliance, HI-SEAS) missions comprised of interdisciplinary, international crews for mock lunar missions. During a six-day mission in March 2024, crew members tested continuous passaging of kefir cultures (C-FIR commercial strain). After approximately 24 hours of growth, a portion of culture was used to seed the next generation of culture bags for four passages. A color board and pH indicator allowed the crew to easily determine when the culture had reached optimal pH. Laboratory analysis at NASA Ames Research Center showed that the pH met Kefir standards (<5). The yeast and lactic acid bacteria were in normal range and no contamination was detected in the final passage. By successfully accomplishing this experiment the team has demonstrated the ability to safely produce daily cultures of kefir in a microgravity applicable growth system.