*2.3. Submerged Fermentation and Bacterial Cellulose (BC) Production*

Cheese whey was pretreated with crude β-galactosidase extracts to break down lactose, and the produced hydrolysates were further evaluated for the production of BC by *A. xylinum*. In addition to that, experiments with unhydrolyzed CW, including initial CW of 50 g/L (A), CW diluted to 25 g/L (B) and CW diluted and supplemented with yeast extract (C), were also performed for comparative reasons. Experiments were conducted in 250 mL Erlenmeyer flasks containing 50 mL of hydrolysate (pH 6.0). The substrate was inoculated with 10% (*v*/*v*) of 48 h bacterial sub-cultures and incubated at 30 ◦C on a 10 days static cultivation. Sugars along with FAN consumption were determined during fermentation. The obtained BC was pretreated as described by Zywicka et al. [ ˙ 31] with slight modifications. Briefly, samples were purified with 0.1% NaOH at 80 ◦C for 30 min to inactivate the bacterial cells and remove medium components. BC membranes were washed in distilled water until the pH stabilized. Further on, the membranes were air-dried at 40 ◦C until constant weight and stored at room temperature for future use [32]. All the experiments were performed in duplicates.
