Current food production methods and consumption behaviours are unsustainable and contribute to environmental harm. One example is food waste—around 38% of food produced is wasted each year. Here, we show that two common food waste products, wheat bran and brewer’s spent grain, can successfully be upcycled via miso fermentation. During the fermentation process, kokumi γ-glutamyl peptides, known to increase mouthfulness, are produced; these include γ-ECG (oxidized), γ-EVG, γ-EV, γ-EE, γ-EF, and γ-EL. The profiles of kokumi peptides and volatile aroma compounds are correlated with koji substrate, pH, and enzymatic activity, offering straightforward parameters that can be manipulated to increase the abundance of kokumi peptides during the fermentation process. Correlation analysis demonstrates that some volatile aroma compounds, such as fatty acid ethyl esters, are correlated with kokumi peptide abundance and may be responsible for fatty, greasy, and buttery aromas. Consumer sensory analysis conveys that the bitter taste of vegetables, such as that in endives, can be dampened when miso extract containing kokumi peptides is added. This suggests that kokumi peptides, along with aroma volatile compounds, can enhance the overall flavour of plant-based products. This study opens new opportunities for cereal processing by-product upcycling via fermentation, ultimately having the potential to promote a plant-based diet.

Space exploration is expanding, which demands new technologies and enables new scientific questions. Food, as a bridge between disciplines, can bring these fundamental and applied goals together. Here we investigate whether food fermentation in space is possible, and if so, how it compares with fermentation on Earth. We fermented a miso, a traditional Japanese condiment, on the International Space Station over 30 days, and compared it with two earthbound controls. Using a specially-built environmental sensing box, we gathered metadata for temperature, relative humidity, pressure, and radiation. We analyzed the three misos with shotgun metagenomics to investigate the microbial communities’ composition and safety; whole genome sequencing to investigate the mutation rate of Aspergillus oryzae ; untargeted metabolomics to quantify aromatic compounds, amino acids and organic acids; colorimetry to quantify color; and sensory analysis to describe the misos’ flavours and quantify liking and sensory difference. Across these datasets, we found that overall, the space miso is recognizable as a miso, suggesting fermentation in space is possible. We also found certain differences in the space miso: specifically the presence of Bacillus velezensis , a higher mutation rate of A. oryzae , higher attributions of ‘roasted’ and ‘nutty’ flavours, and the most different sensory impression. Taken together, these observations suggest unique features of the space environment—what we might call ‘space terroir’—which could be harnessed to create more flavorful, nourishing foods for long-term space missions and to address fundamental questions about the biology of novel environments. Significance Statement: Our study presents, to our knowledge, the first time a food product has been fermented in space. We demonstrate that fermentation in space is possible with safe and successful results, a proof of concept that offers fermentation as a new tool for space research and future long-term space exploration missions. We also document how the space environment shapes the fermentation process in unique ways, suggesting a ‘space terroir’. These findings on the feasibility and novelty of fermentation in space open up directions for further multidisciplinary research across science, health, systems design, and society and culture.

Current food production methods and consumption behaviours are unsustainable and contribute to environmental harm. One example is food waste  around 38% of food produced is wasted each year. Here, we show that two common food waste products, wheat bran and brewer’s spent grain, can successfully be upcycled via miso fermentation. During the fermentation process, kokumi g-glutamyl peptides, known to increase mouthfulness, are produced; these include g-ECG (oxidized), g-EVG, g-EV, g-EE, g-EF, and g-EL. The profiles of kokumi peptides and volatile aroma compounds are correlated with koji substrate, pH, and enzymatic activity, offering straightforward parameters that can be manipulated for increasing the abundance of kokumi peptides during the fermentation process. Correlation analysis demonstrates that some volatile aroma compounds, such as fatty acid ethyl esters, are correlated with kokumi peptide abundance and may be responsible for the fatty, greasy, and buttery aroma. Consumer sensory analysis conveys that the bitter taste of vegetables, such as that in endives, can be dampened when miso extract containing kokumi peptides is added. This suggests that kokumi peptides, along with aroma volatile compounds, can enhance the overall flavor in plant-based products. This study opens new opportunities for cereal processing by-product upcycling via fermentation, ultimately having the potential to promote a plant-based diet.