Impact of Whey and Sucrose Concentrations on Bacterial Cellulose Characteristics for Functional Food Applications

Bacterial cellulose (BC) shows high potential for food applications, yet its scalable production using whey-based substrates remains challenging. The aim of the study was to evaluate the influence of whey (40–100% v/v) and sucrose (0–50 g·L−1) concentrations on BC synthesis in a medium formulated with black tea. Static cultures (28 ± 2 °C, 15 days) were carried out using an inoculum of 25% (v/v) of an adapted microbial consortium and compared to a whey-free control. The structural, physicochemical, and functional properties of BC were characterized by dry mass yield, hygroscopicity, FTIR, XRD, SEM, transparency, and mechanical tests. Although it did not alter the chemical structure of BC, whey exerted a strong impact on its synthesis: the formulation with the highest whey and sucrose contents showed the highest yield (9.56 ± 1.76 g·L−1), with fibrils ranging in diameter from 50 to 100 nm. Although crystallinity decreased (57.30%), this result did not impair mechanical performance; on the contrary, such a treatment resulted in the highest tensile strength (13.43 ± 2.30 Mpa). Thus, modulating whey and sucrose concentration proves to be an effective strategy for adjusting the structural and functional properties of BC, highlighting the potential of the selected byproducts as low-cost substrates for technological applications in the food sector.