(351b) Alternative Feedstock Utilization By the Rhodococcus Jostii Strain PET for Biomanufacturing Beyond Earth

Biomanufacturing at alternative habitats is drawing attention in space research. Using productive microbes as laborers presents a strategy to overcome cost limitations and waste generation of space exploration. This study investigated the potential of three different alternative feedstocks sourced or found beyond Earth: Regolith for micronutrients, Deconstructed polyethylene terephthalate (PET) for carbon, and Permeate from an anaerobic membrane bioreactor (AnMBR) treating fecal waste for macronutrients. This study aims to develop and optimize the chemical process for using Rhodococcus jostii strain PET (RPET) as a promising chassis to upcycle post-consumer PET into value-added chemicals (i.e., lycopene) in an alternative medium. For a partial alternative medium, regolith simulant was added into a reduced medium containing only carbon (PET monomers), nitrogen, and phosphorus. For a completely alternative medium, the nitrogen and phosphorus sources were replaced by AnMBR permeate. In these experimental settings, the successful utilization of alternative resources by RPET for valuable product generation was demonstrated.

First, regolith simulant supported RPET growth as a micronutrient source through bioleaching from ore particles and utilizing acidified regolith leachate. With 1 g/L dosage of lunar and Martian regolith simulant particles, growth achieved 66 % and 117 %, respectively, compared to the conventional medium. The active biosorption by the organic acid formation facilitated nutrient uptake, including calcium, magnesium, and iron. From the tolerance test to the acidified regolith leachate, RPET exhibited robustness against metal ions such as aluminum, titanium, and chromium present in regolith simulants that are supposed to be toxic to the strain. Second, regolith simulant enhanced the lycopene production, with Martian regolith simulant particles resulting in a 1.6 times higher yield compared to the conventional medium. Lunar regolith simulant achieved similar levels despite lower growth and carbon source consumption, indicating effective simulant utilization. The efficiency may be possibly due to enhanced activation of iron-related carotenoid enzymes. Regolith simulants are rich in iron, particularly the red-colored Martian regolith simulants. Third, in the completely alternative medium, where 40% AnMBR permeate was diluted in the water, growth levels were comparable to those in the conventional medium, even without the regolith simulant. The nutrient diversity of the wastewater other than nitrogen and phosphorus provided effective growth support. Lycopene production increased by 1.4 times in the presence of regolith simulant, which supplemented the trace elements lacking in the permeate that can support the lycopene producing pathway. Furthermore, the microbial growth and lycopene production have been tested in microgravity simulating high aspect ratio vessels to verify the feasibility of both partial and completely alternative feedstock utilizing medium in lower gravity conditions than Earth.

In summary, the viability of utilizing alternative feedstock was affirmed, and the potential recipe for RPET cultivation in space was proposed. This approach will contribute to space biomanufacturing research by significantly reducing space mission costs and advancing sustainable habitat construction in extraterrestrial environments.