Tailored ethylenediamine-functionalized graphene oxide membrane on kaolin hollow fibers for pectin concentration.

Pectin is a valuable product that can be extracted from waste fruit peels. Here we propose the use of graphene oxide (GO)-based membranes for pectin concentration. The synthesized GO was functionalized with ethylenediamine (EDA) to molecularly design the GO framework. Kaolin hollow fibers with asymmetric pore distribution were used as a porous substrate for GO/EDA deposition. A GO/EDA layer with a thickness of 2.86 ± 0.24 µm was assembled on the substrate by the simple vacuum-assisted deposition method. After GO/EDA depositions, the water permeance of the pristine kaolin hollow fibers reduced from 8.46 ± 0.17 to 0.52 ± 0.03 L h-1·m-2·kPa-1. A pectin aqueous extract from orange peels was filtered at cross-flow mode through the prepared membranes and the steady-state fluxes through pristine and GO/EDA-coated hollow fibers were 56 ± 2 and 20 ± 3 L h-1 m-2, respectively. The GO/EDA-coated membrane presented greater pectin selectivity than the pristine hollow fiber. The GO/EDA-coated hollow fiber concentrated the galacturonic acid, phenolic, and methoxyl contents in 19.5, 17.4, and 29.2 %, respectively. Thus, filtration through the GO/EDA-based membrane is a suitable alternative for pectin concentration.

Biolixiviation of Metals from Computer Printed Circuit Boards by Acidithiobacillus ferrooxidans and Bioremoval of Metals by Mixed Culture Subjected to a Magnetic Field.

Crushed and ground printed circuit board (PCB) samples were characterized to evaluate copper, lead, and aluminum using X-ray fluorescence spectroscopy (XRF) and the morphology was done by scanning electron microscopy (SEM). The XRF characterizations showed 0.12% lead, 3.72% copper, and 12.73% aluminum in the PCBs. The metal solubilization experiments using Acidithiobacillus ferrooxidans indicated higher values of total metal solubilization when the initial pH of the inoculum was adjusted. However, these experiments did not show higher metal solubilization by bioleaching. The sequential bioremoval experiments using mixed culture after bioleaching assays with A. ferrooxidans with initial adjustment of inoculum pH and without applying a magnetic field removed 100% of Al, 27.34% of Cu, and 96.43% of Pb from the lixiviate medium; with magnetic field application, 100% of Al, 83.82% of Cu, and 98.27% of Pb were removed. A similar bioleaching experiment without inoculum pH adjustment and without field application achieved 99.74% removal for Cu and 91.92% for Pb. When the magnetic field was applied, 100% of Cu and 95.76% of Pb were removed. Bioreactors with a magnetic field do not show significantly better removal of any of the metals analyzed.

Leaching with mixed organic acids and sulfuric acid to recover cobalt and lithium from lithium ion batteries.

Li-ion batteries (LIBs) should be recycled because of the environmental reasons and this type of waste represents an important secondary source of metals. This work aimed to evaluate the recovery of Co and Li from LIBs by hydrometallurgy. The efficiency of different leachants was tested: H2SO4 (2 M), fermentation effluent with supplementation of organic acids (lactic, acetic, butyric and propionic acids) (3.4 M) and a combination of fermentation effluent (0.75 M) and H2SO4 (1.25 M). In addition, the effect of H2O2, glucose P.A., lactose P.A. and from milk whey permeate (MWP) as reducing agent was tested. The leaching solution composed of H2SO4 and fermentation effluent showed high potential of metals recovery in addition to being an alternative of reducing the volume of inorganic acid and the cost by using a fermentation effluent since its use may be integrated with a waste treatment process. Based on Central Composite Designs, optimum conditions of leaching were established, as temperature of 86°C, solid-liquid ratio of 18.5 g/L, leaching time 2.5 h, agitation of 300 rpm and concentration of 0.09 M of lactose from MWP and recovery level achieved was 93.35% of Co and 90.50% of Li. In order to evaluate the influence of each organic acid present on the fermentation effluent, testes were carried out using pure organic acid with H2SO4 (0.75 M:1.25 M) or isolated (3.4 M) and inferior recoveries were detected proving that mixture of organic acids and further compounds as phenolic groups characteristic of fermentation effluent improves the leaching process.

Dark fermentation effluent as substrate for hydrogen production from Rhodobacter capsulatus highlighting the performance of different fermentation systems.

Hydrogen production by biological route is a potentially sustainable alternative. Nowadays, energy production from sustainable sources has become urgent for several countries as well as for international policies. In this perspective, hydrogen has gained substantial global attention as clean, sustainable, and versatile energy carrier. In the current work, the resulting effluent from dark fermentation, rich in organic acids, was used as substrate for the purple non-sulfur bacteria (PNS) Rhodobacter capsulatus. In the first stage, experiments were carried out in bioreactors of 50 mL to check the influence of the composition of the effluent dark fermentation. The results proved that the provision of a sugar source improved bio-H2 production. The lactose and lactic acid concentrations exceeding 4.4 and 12 g/L, respectively, resulted in a productivity of up to 37.14 mmol H2/L days. Based on initial conditions obtained on the previous assays, in the second stage, a photo-fermentation in enlarged scale (1.5 L) was performed with the purpose to monitor the production of hydrogen and metabolites, sugar consumption and growth cells during the process. It was observed that the maximum productivity obtained was 98.23 mmol H2/L days in 26 h of process.

Alternative techniques to improve hydrogen production by dark fermentation.

The production of biofuels as an alternative to the fossil fuels has been mandatory for a cleaner and sustainable process. Hydrogen is seen as the fuel of the future because it has a very high energy density and its use produces only water instead of greenhouse gases and other exhaust pollutants. The biological synthesis of hydrogen by dark fermentation complies with these criteria. In the current work, the use of cheese whey permeate was evaluated aiming hydrogen production by dark fermentation using a microbial consortium in the semi-continuous process, with a reaction volume of 700 mL. The volume of the medium renewal and the frequency of replacements of fresh medium were evaluated to extend the production of H2. It is important to note decreases in the hydrogen production after 84 h. The target-product content became higher particularly when 466 mL of medium were withdrawn, in every 24 h in the first two replacements and, subsequently, in every 12 h. Besides, it was observed lower lactic acid concentration under this condition, suggesting that the shorter removal time of the medium could inhibit lactic acid bacteria, which may secrete bacteriocins that inhibit the hydrogen-producing microorganisms.

Soy molasses as a fermentation substrate for the production of biosurfactant using Pseudomonas aeruginosa ATCC 10145.

Soy molasses is a product co-generated during soybean processing that has high production and low commercial value. Its use has great potential in fermentative processes due to the high concentration of carbohydrates, lipids and proteins. This study investigated the use of Pseudomonas aeruginosa to produce biosurfactants in a soy molasses-based fermentation medium. A central composite design (CCD) was prepared with two variables and three replicates at the central point to optimize the production of biosurfactant. The concentration of soy molasses had values between 29.3 and 170.7 g/L and the initial concentration of microorganism varied between 0.2 and 5.8 g/L. All the experiments were performed in duplicate on a shaker table at 30.0 ± 1.0 °C and 120 rpm for 72 h with samples taken every 12 h. Thus, to validate the experiments, the values of 120 g/L for the initial concentration of soy molasses and 4 g/L for the initial concentration of microorganisms were used. In response, the following values were obtained at 48 h of fermentation: surface tension of 31.9 dyne/cm, emulsifying index of 97.4%, biomass concentration of 11.5 g/L, rhamnose concentration of 6.9 g/L and biosurfactant concentration of 11.70 g/L. Further analysis was carried out for critical micelle concentration (CMC) which was obtained at approximately 80 mg/L. The bands found in Fourier transform infrared spectroscopy analysis had characteristic glycolipids as reported in the literature. These values show a great potential for biosurfactant production using soy molasses as a substrate and bacteria of the species P. aeruginosa.

Optimization of the production and characterization of lipase from Candida rugosa and Geotrichum candidum in soybean molasses by submerged fermentation.

This present work describes the production and biochemical characterization of lipase by Candida rugosa and Geotrichum candidum in a culture supplemented with soybean molasses. After optimizing the fermentation times for both microorganisms, the effects of changing the soybean molasses concentration, the fermentative medium pH and the fermentation temperature were evaluated using the Central Composite Planning. When soybean molasses was used at a concentration of 200 g/L at 27 ± 1 °C and pH 3.5, the lipolytic activity measured in the broth was 12.3 U/mL after 12 h for C. rugosa and 11.48 U/mL after 24 h for G. candidum. The molecular masses were 38.3 kDa to G. candidum lipase and 59.7 kDa to C. rugosa lipase, determined by SDS-PAGE. The lipase from both microorganisms exhibited maximal hydrolytic activity at a temperature of 40 °C and were inhibited at pH 10.0. Using different concentration of p-nitrophenylbutyrate (p-NPB), the kinetic parameters were calculated, as follows: the Km of lipase from G. candidum was 465.44 µM and the Vmax 0.384 µmol/min; the Km and Vmax of lipase from C. rugosa were 129.21 µM and 0.034 µmol/min, respectively. Lipases activity were increased by metallic ions Mg(2+) and Na(+) and inhibited by metallic ion Cu(3+).

Bio-oil production and removal of organic load by microalga Scenedesmus sp. using culture medium contaminated with different sugars, cheese whey and whey permeate.

The objective of this study was to evaluate the bio-oil production and the organic load removal using the microalga Scenedesmus sp. The cultivation was carried out in reactors with a total volume of 3 L and 0.7 vvm aeration, with illumination in photoperiods of 12 h light/12 h dark for 12 days. The following sugar concentrations were tested: 2.5, 5.0 and 10 g/L of glucose, lactose, fructose and galactose with 10% inoculum volume. After experiments were performed with cheese whey in natura and cheese whey permeate with different lactose concentrations (1.5, 2.5, 3.5 and 5.0 g/L). In these experiments the inoculum concentrations were 10, 15, 20 and 30% (v/v). The results showed that this microalga was effective for the production of lipids when it was cultivated in medium with cheese whey in natura with 2.5 g/L of lactose and 20% inoculum (v/v). Using cheese whey in natura at the concentration of 3.5 g/L of lactose and 30% (v/v) of inoculum obtained 77.9% of TOC removal and 38.447 mg of TOC removed/mg oil produced. It was also observed that when there is increased production of bio-oil, there is less removal of organic matter. The addition of glucose, fructose or galactose in the medium did not enhance the production of bio-oil by Scenedesmus sp. when compared to lactose, but increased the organic matter removal.

Replacement of sugars to hydrogen production by Rhodobacter capsulatus using dark fermentation effluent as substrate.

Hydrogen is a promising alternative for the increased global energy demand since it has high energy density and is a clean fuel. The aim of this work was to evaluate the photo-fermentation by Rhodobacter capsulatus, using the dark fermentation effluent as substrate. Different systems were tested by changing the type of sugar in the dark fermentation, investigating the influence of supplementing DFE with sugar and adding alternate and periodically lactose and glucose throughout the process. The supplementation of the DFE with sugar resulted in higher H2 productivity and the replacement of the sugars repeatedly during the photo-fermentation process was important to maintain the cell culture active. By controlling the residual amount of sugar, bacteria inhibition was avoided; lactic acid, that was toxic to the biomass, was consumed and the metabolic route of butyric acid production was predominant. Under optimum conditions, the H2 productivity reached 208.40mmolH2/Ld in 52h.

Prospective technology on bioethanol production from photofermentation.

The most important global demand is the energy supply from alternative source. Ethanol may be considered an environmental friendly fuel that has been produced by feedstock. The production of ethanol by microalgae represent a process with reduced environmental impact with efficient CO2 fixation and requiring less arable land. This work studied the production of ethanol from green alga Chlamydomonas reinhardtii through the cellular metabolism in a light/dark cycle at 25 °C in a TAP medium with sulfur depletion. The parameters evaluated were inoculum concentration and the medium supplementation with mixotrophic carbon sources. The combination of C.reinhardtii and Rhodobacter capsulatus through a hybrid or co-culture systems was also investigated as well. C.reinhardtii maintained in TAP-S produced 19.25±4.16 g/L (ethanol). In addition, in a hybrid system, with medium initially supplemented with milk whey permeated and the algal effluent used by R. capsulatus, the ethanol production achieved 19.94±2.67 g/L.

Alcoholic fermentation with flocculant Saccharomyces cerevisiae in fed-batch process.

Studies have been conducted on selecting yeast strains for use in fermentation for ethanol production to improve the performance of industrial plants and decrease production costs. In this paper, we study alcoholic fermentation in a fed-batch process using a Saccharomyces cerevisiae yeast strain with flocculant characteristics. Central composite design (CCD) was used to determine the optimal combination of the variables involved, with the sucrose concentration of 170 g/L, a cellular concentration in the inoculum of 40% (v/v), and a filling time of 6 h, which resulted in a 92.20% yield relative to the theoretical maximum yield, a productivity of 6.01 g/L h and a residual sucrose concentration of 44.33 g/L. With some changes in the process such as recirculation of medium during the fermentation process and increase in cellular concentration in the inoculum after use of the CCD was possible to reduce the residual sucrose concentration to 2.8 g/L in 9 h of fermentation and increase yield and productivity for 92.75% and 9.26 g/L h, respectively. A model was developed to describe the inhibition of alcoholic fermentation kinetics by the substrate and the product. The maximum specific growth rate was 0.103 h(-1), with K(I) and K(s) values of 109.86 and 30.24 g/L, respectively. The experimental results from the fed-batch reactor show a good fit with the proposed model, resulting in a maximum growth rate of 0.080 h(-1).

Use of a greasy effluent floater treatment station from the slaughterhouse for biosurfactant production.

Most commercially available surfactants are produced from petroleum. However, increasing concerns about the environment have stimulated the search for biosurfactant production. This work examines biosurfactant production from the greasy effluent floater treatment station from the slaughterhouse of poultry and pigs. The biosurfactant production was evaluated using two strains of Pseudomonas aeruginosa [American Type Culture Collection (ATCC) 9027 and 10145] in a kinetic study to determine which strain produces a higher rhamnolipid concentration, which is characterized by the rhamnose concentration. The strain of P. aeruginosa was selected via a central composite design based on the following variables: fat concentration, nitrogen concentration, added ammonium nitrate (AN), and brewery residual yeast (BRY). The preliminary results show that the P. aeruginosa strain ATCC 10145 produced biosurfactant more efficiently than ATCC 9027. After optimizing the variables that were studied, the best fat, BRY, and AN concentrations (in g/L) were found to be 12, 15, and 0, respectively.

Evaluation of hexavalent chromium removal in a continuous biological filter with the use of central composite design (CCD).

Hexavalent chromium is frequently found in industrial effluents as a result of the industrial applications of this compound and its anti-corrosive features. However, hexavalent chromium is extremely toxic, and its discharge in water is regulated, with a maximum limit of 0.1 mg/L in accordance with legislation established by CONAMA-Brazil (no. 397, April 3, 2008). To achieve lower discharge values, it is necessary to reduce from Cr(VI) to Cr(III), which is less toxic, and an economic alternative involves biological removal of this compound. Residence time distributions (RTDs) were measured to evaluate the behavior of actual biofilter operation conditions in a biofilter flow. The medium residence time distributions used were 8 and 24 h (recommended by the legislation). To optimize this process, a central composite design was used, considering the initial chromium concentration and pH as the independent variables and the removal of hexavalent chromium as the response. The boundary curves and surface response showed optimal behavior at 3.94 mg/L [Cr(0)] and a pH of 6.2. The removal process of hexavalent chromium is mathematically described by the Michaelis-Menten kinetic model. This model appropriately represents the variation of chromium concentration along the bioreactor.