RESUMO
In this work, we performed recovery of ethanol from a fermentation broth of banana pseudostem by pervaporation (PV) as a lower-energy-cost alternative to traditional separation processes such as distillation. As real fermentation systems generally contain by-products, it was investigated the effects of different components from the fermentation broth of banana pseudostem on PV performance for ethanol recovery through commercial flat sheet polydimethylsiloxane (PDMS) membrane. The experiments were compared to a binary solution (ethanol/water) to determine differences in the results due to the presence of fermentation by-products. A real fermented broth of banana pseudostem was also used as feed for the PV experiments. Seven by-products from fermented broth were identified: propanol, isobutanol, methanol, isoamyl alcohol, 1-pentanol, acetic acid, and succinic acid. Moreover, the residual sugar content of 3.02 g/L1 was obtained. The presence of methanol showed the best results for total permeate flux (0.1626 kg·m-2 ·h-1 ) and ethanol permeate flux (0.0391 kg·m-2 ·h-1 ) during PV at 25°C and 3 wt% ethanol, also demonstrated by the selectivity and enrichment factor. The lowest total fluxes of permeate were observed in the experiments containing the acids. Better permeance of 0.1171 from 0.0796 kg·m-2 ·h-1 and membrane selectivity of 9.77 from 9.30 were obtained with real fermentation broth than with synthetic solutions, possibly due to the presence of by-products in the multicomponent mixtures, which contributed to ethanol permeation. The results of this work indicate that by-products influence pervaporation of ethanol with hydrophobic flat sheet membrane produced from the fermented broth of banana pseudostem.
Assuntos
Etanol/isolamento & purificação , Fermentação , Musa/metabolismo , Dimetilpolisiloxanos/química , Dimetilpolisiloxanos/metabolismo , Etanol/química , Etanol/metabolismo , Hidrólise , Musa/química , Ácidos Sulfúricos/química , Ácidos Sulfúricos/metabolismo , VolatilizaçãoRESUMO
ß-glucosidase from almonds was immobilized on a polydimethylsiloxane (PDMS) microdevice by covalent chain using 3-aminopropyltrietoxysilane and glutaraldehyde. Enzymatic activity was evaluated using p-nitro-phenyl-ß-D-glucopyranoside dissolved in a 0.01â¯M pH 5.0 phosphate solution at 45⯰C measuring the reaction product (p-nitrophenol) at 410â¯nm. The microdevice consisted of two parts: the one part where the enzymatic reaction was carried out and a second part where pH was adjusted at 10, with NaOH. The reaction product was measured at the microchip exit using two optical fibers which were aligned facing each other with a gap of 7â¯mm, between both tips using guides located perpendicular to the flow outlet. A water bath was used to carry out the enzymatic reaction on the microdevice at 45⯰C. The enzymatic surface of the PDMS microdevice was 1.15â¯cm2 and the immobilized ß-glucosidase amount on the microdevice was of 1.17⯵g/cm2. The calculated kinetics parameters were: Km 2.5â¯mM; Vmax 2.2â¯mM/min; Kcat 908.3/min and Kcat/Km 363.3/mM min. The immobilized enzyme is very stable decreasing only 5% the first 15 days; on the 30th day, the activity was 69%, regarding the initial activity.
Assuntos
Dimetilpolisiloxanos/metabolismo , Enzimas Imobilizadas/metabolismo , Análise de Injeção de Fluxo , Técnicas Analíticas Microfluídicas , Fibras Ópticas , beta-Glucosidase/metabolismo , Dimetilpolisiloxanos/químicaRESUMO
The aims of this study were to evaluate the effects of the addition of metabolic precursors and polydimethylsiloxane (PDMS) as an oxygen carrier to cultures of Bacillus subtilis BL53 during the production of γ-PGA. Kinetics analyses of cultivations of different media showed that B. subtilis BL53 is an exogenous glutamic acid-dependent strain. When the metabolic pathway precursors of γ-PGA synthesis, L-glutamine and a-ketoglutaric acid, were added to the culture medium, production of the biopolymer was increased by 20 % considering the medium without these precursors. The addition of 10 % of the oxygen carrier PDMS to cultures caused a two-fold increase in the volumetric oxygen mass transfer coefficient (kLa), improving γ-PGA production and productivity. Finally, bioreactor cultures of B. subtilis BL53 adopting the combination of optimized medium E, added of glutamine, α-ketoglutaric acid, and PDMS, showed a productivity of 1 g L(-1) h(-1) of g-PGA after only 24 h of cultivation. Results of this study suggest that the use of metabolic pathway precursors glutamine and a-ketolgutaric acid, combined with the addition of PDMS as an oxygen carrier in bioreactors, can improve γ-PGA production and productivity by Bacillus strains .