No abstract

Production of bacterial cellulose hydrogel and its evaluation as a proton exchange membrane (PEM) was evaluated. Initially, the bacterial cellulose hydrogel membranes (BCH) was produced by fermentation in a 600 mL bioreactor with a 300 mL medium volume, 10% v/v inoculum with Komagataeibacter hansenii under static conditions, and a temperature of 30 °C. The bacteria were cultivated in Hestrin-Schramm (HS) medium with pH adjustment to 6.6 with HCl and/or NaOH. Five culture media were evaluated to obtain uniformity on the surface and a rapid formation of BCH membrane: HS (M1), M1 + green tea extract (M3), M1 + mixture of extra thyme and green tea (M4), and M1 + glycerin (M5). The kinetics of BCH production was followed by digital images. Subsequently, BCH production cellulose was carried out using M5 under the same operating conditions. After 3, 5, 10 and 13 days of fermentation, the thickness of BCH formed was measured, respectively, as 0.301 ± 0.008 cm, 0.552 ± 0.026 cm, 0.584 ± 0.03 cm and 0.591 ± 0.018 cm. Finally, BCH was characterized by porosity, water absorption capacity, ion exchange capacity, mechanical strength and diffusivity. The results showed that thinner membranes favor the processes of ion exchange (0.143 H+mmol g−1) and water absorption (93%). On the other hand, thicker membranes enhance physical parameters of transport across the membrane and its operability. Nevertheless, BCH membranes can be a good alternative as PEM to microbial fuel cell once they are functionalized.

The biotransformation of rice husk ash (RHA) by Fusarium oxysporum to generate silica nanoparticles was carried out using two different commercial growth media: malt-glucose (MG) and malt-glucose-yeast-peptone (MGYP). Biomass production, substrate consumption, organic acids production, and solubilized silica were measured during RHA biotransformation. Extracellular proteins were analyzed by SD-PAGE. Silica nanoparticles were analyzed by XRD, zeta potential, SEM, and TEM. The results showed that the production of organic acids was not directly related to the solubilization of silica. Solubilization and stabilization of silica occur mainly in the exponential growth phase of F. oxysporum, which are associated with the action of extracellular proteins with sizes 24, 55, and 70 kDa. MG medium presented the best performance for the growth of F. oxysporum and production of semicrystalline, quasi-spherical silica nanoparticles in the range of 2−8 nm.

No abstract