Bacterial cellulose (BC) is a valuable biopolymer typically observed in Kombucha with many potential food applications. Many studies highlight yeast's roles in providing reducing sugars, used by the bacteria to grow and produce BC. However, whether yeast could enhance the BC yields remains unclear. This study investigates the effect of yeast Dekkera bruxellensis on bacteria Komagataeibacter intermedius growth and BC production in molasses medium. The results showed that the co-culture stimulated K. intermedius by similar to 2 log CFU/mL, which could be attributed to enhanced reducing sugar utilization. However, BC yields decreased by similar to 24%, suggesting a negative impact of D. bruxellensis on BC production. In contrast to other studies, regardless of D. bruxellensis, K. intermedius increased the pH to similar to 9.0, favoring the BC production. Furthermore, pH increase was slower in co-culture as compared to single culture cultivation, which could be the reason for lower BC yields. This study indicates that co-culture could promote synergistic growth but results in the BC yield reduction. This knowledge can help design a more controlled fermentation process for optimum bacterial growth and, ultimately, BC production.