Dra. Núñez-Bernal, Dariela

Bacterial nanocellulose (BNC) is a sustainable, renewable, and eco-friendly nanomaterial, which has gained great attentions in both academic and industrial fields. Two bacterial nanocellulose-producing strains (CVV and CVN) were isolated from apple vinegar sources, presenting high 16S rRNA gene sequence similarities (96%–98%) with Komagataeibacter species. The biofilm was characterized by scanning electron microscopy (SEM), revealing the presence of rod-shaped bacteria intricately embedded in the polymeric matrix composed of nanofibers of bacterial nanocellulose. FTIR spectrum and XRD pattern additionally confirmed the characteristic chemical structure associated with this material. The yields and productivities achieved during 10 days of fermentation were compared with Komagataeibacter xylinus ATCC 53524, resulting in low levels of BNC production. However, a remarkable increase in the BNC yield was achieved for CVV (690% increase) and CVN (750% increase) strains at day 6 of the fermentation upon adding 22 mM citrate buffer into the medium. This effect is mainly attributed to the buffering capacity of the modified Yakamana medium, which allowed to maintain pH close to 4.0 until day 6, though in combination with additional factors including stimulation of the gluconeogenesis pathway and citrate assimilation as a carbon source. In addition, the productivities determined for both isolated strains (0.850 and 0.917 g L−1 d−1) compare favorably to previous works, supporting current efforts to improve fermentation performance in static cultures and the feasibility of scaling-up BNC production in these systems.

The adsorption capacity of hydrogels derived from modified xylan hemicellulose has been tested in order to develop new bio-based adsorbent materials useful for removing metal ions pollutants, such as Cd(II), Cu(II) and Pb(II) from an aqueous solution. Xylan was extracted from bleached kraft pulp of eucalyptus and subsequently modified with different proportions of functional sulfonic acid groups (HA3–HA7) and sulfonate groups (HS30–HS70) to generate hydrogels. The results showed that all the synthesized hydrogels were capable of adsorbing metal ions, being the hydrogels with 30% and 50% xylan the ones that presented the highest adsorption capacity. Maximum capacity studies at different initial concentrations revealed that at an initial concentration of 300 mg·L−1, the HA3 hydrogel presented an adsorption capacity of 193 mg Pb(II), 182 mg Cd(II), and 66 mg Cu(II) per g hydrogel. The HA5 hydrogel presented a capacity of 185 mg Pb(II), 113 mg Cd(II), and 48 mg Cu(II) per g hydrogel. The HS30 hydrogel exhibited an adsorption of 205 mg Pb(II), 174 mg Cd(II), and 71 mg Cu(II) per g hydrogel, and HS50 hydrogel exhibited an adsorption capacity of 273 mg Pb(II), 143 mg Cd(II), and 45 mg Cu(II) per g hydrogel. These results show that modified Xylan hemicellulose is a promising adsorbent for removal Cd(II), Cu(II), and Pb(II) ions from aqueous solutions.