**5.2 Chitosan/TiO2 film production**

Following the procedure for polymer solution casting, we measured and mixed chitosan powder with acetic acid and deionized water following this schedule: a mechanical agitator for 1.5 h, a sonicator for 1 h, and a magnetic agitator for another 1 h. The TiO2 powder (anatase polymorph) was added in increments of 0.5 wt% to reach each target concentration and to prepare four different mixtures of TiO2 and chitosan. These mixtures were left inside an oven at 55°C for 48 hrs to be then utilized and characterized. **Figure 4** shows the as-produced films ready to be tested.

**Figure 4.** *Films as extracted from the oven. (A) 0.0% TiO2, (B) 0.5% TiO2, (C) 1.0% TiO2, and (D) 1.5% TiO2.*

## **5.3 Bacteria medium preparation for growth curve analysis**

In this protocol, we prepared the bacterial medium of Luria broth (LB) nearly 24 h before each experiment. All laboratory glassware was autoclaved for 15 minutes before use. One liter of water was mixed with 10 g of LB assisted by a magnetic agitator. After obtaining a visually homogenous mixture, we divided it in three groups of laboratory plastic tubes, namely, control, *E. coli*, and *S. aureus*, and autoclaved a second time for 15 minutes. Each bacteria medium was left overnight inside a fume hood under UV light. Two master solutions were separated from the group, incubated with the bacteria, and left inside a shaker at 200 rpm and 37.0°C for almost 6 h. We followed this entire procedure twice per experiment to produce enough samples to be tested with and without UV.
