| Summary: | In the present work, the modification of spent coffee grounds (SCG) hydrolysate composition by mixed cultures of a non-<i>Saccharomyces</i> yeast, <i>Lachancea thermotolerans</i>, and a lactic acid bacterium, <i>Lactiplantibacillus plantarum</i>, as well as their interactions, were evaluated. It was found that <i>L. plantarum</i> inhibited the growth and survival of <i>L. thermotolerans</i> as compared with that in the yeast alone. On the other hand, the growth and survival of <i>L. plantarum</i> was slowed in sequential fermentation, but not in co-culture. Compared with co-culture, higher ethanol content, less residual sugars, and less acetic and succinic acids were found in sequential fermentation. In addition, lower amounts of caffeine and phenolic acids (e.g., ferulic, caffeic, and p-coumaric acids) were obtained in mixed (co- and sequential) cultures with corresponding levels of volatile phenols relative to the yeast monoculture. Moreover, co-culturing resulted in the highest contents of total alcohols (ethanol excluded) and total esters. Therefore, mixed culturing of <i>L. plantarum</i> and <i>L. thermotolerans</i> presented positive effects on the chemical constituents of fermented SCG hydrolysates, which might be a new alternative approach to valorizing the SCG into novel alcoholic drinks with different ethanol and flavor constituents.
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