Engineering Synthetic Microbial Communities through a Selective Biofilm Cultivation Device for the Production of Fermented Beverages

Production of Cambodian rice wine involves complex microbial consortia. Indeed,
previous studies focused on traditional microbial starters used for this product revealed that three
microbial strains with complementary metabolic activities are required for an e ective fermentation,
i.e., filamentous fungi (Rhizopus oryzae), yeast (Saccharomyces cerevisiae), and lactic acid bacteria
(Lactobacillus plantarum). Modulating the ratio between these three key players led to significant
di erences, not only in terms of ethanol and organic acid production, but also on the profile of
volatile compounds, in comparison with natural communities. However, we observed that using an
equal ratio of spores/cells of the three microbial strains during inoculation led to flavor profile and
ethanol yield close to that obtained through the use of natural communities. Compartmentalization
of metabolic tasks through the use of a biofilm cultivation device allows further improvement of the
whole fermentation process, notably by increasing the amount of key components of the aroma profile
of the fermented beverage (i.e., mainly phenylethyl alcohol, isobutyl alcohol, isoamyl alcohol, and
2-methyl-butanol) and reducing the amount of o -flavor compounds. This study is a step forward
in our understanding of interkingdom microbial interactions with strong application potential in
food biotechnology.