Waste Fe/Cr sludge as flocculant for the treatment of dairy wastewater

Variation in the characteristics of dairy wastewater with storage time is shown. The efficiency of Fe³⁺/Cr³⁺ sludge, a waste material from the wastewater treatment in the fertilizer industry, is compared with the conventional flocculants, ferric chloride and ferrous sulphate, in the treatment of dairy wastewater. The percentage removals of turbidity, BOD, COD, oil and grease and total phosphate were 81 ± 5, 68 ± 5, 70 ± 5, 52 ± 5 and 70 ± 5 respectively, by 1·043 g dosage of sludge per litre of the effluent, and the pH of the treated water was 5·7.     

Chitosan Interactions with Metal Ions and Dyes: Dissolved-state vs. Solid-state Application

Summary Chitosan is an amino-polysaccharide with highly efficient properties for the binding of metal ions and anionic dyes. Uptake may occur through chelation on free amino functions (at near-neutral pH) or by electrostatic attraction on protonated amino groups (in acidic solutions). The polymer is soluble in acidic solutions and its binding properties can be used in both solid form (sorption) and liquid form (ultrafiltration coupled with chelation, coagulation–flocculation). These properties have been used for the recovery of mercury from dilute solutions at initial pH 5 (which reveals the most efficient pH in the range pH 4–6) and for the recovery of Reactive Black 5 (RB5, anionic dye) at pH 3. While in the case of mercury binding saturation of the biopolymer is only slightly higher when chitosan is used in the liquid form compared to solid-state adsorption, in the case of the coagulation–flocculation of RB5 (using the liquid-form of chitosan) the saturation of the polymer (calculated on the basis of molar ratio of dye vs. amino groups of the polymer) is reached at a significantly greater value than when the polymer is used for the solid-state binding of the dye. There is a much more efficient use of amino groups when chitosan is used in the liquid-form due to a better availability of amino groups (less hydrogen bonds between the chains of the polymer) and to a better accessibility to internal sorption sites (lower diffusion control).     

Comparison of different artificial neural network architectures in modeling of Chlorella sp. flocculation

Biodiesel production from microalgae feedstock should be performed after growth and harvesting of the cells, and the most feasible method for harvesting and dewatering of microalgae is flocculation. Flocculation modeling can be used for evaluation and prediction of its performance under different affective parameters. However, the modeling of flocculation in microalgae is not simple and has not performed yet, under all experimental conditions, mostly due to different behaviors of microalgae cells during the process under different flocculation conditions. In the current study, the modeling of microalgae flocculation is studied with different neural network architectures. Microalgae species, Chlorella sp., was flocculated with ferric chloride under different conditions and then the experimental data modeled using artificial neural network. Neural network architectures of multilayer perceptron (MLP) and radial basis function architectures, failed to predict the targets successfully, though, modeling was effective with ensemble architecture of MLP networks. Comparison between the performances of the ensemble and each individual network explains the ability of the ensemble architecture in microalgae flocculation modeling.     

Combining chemical flocculation and bacterial co-culture of Cupriavidus taiwanensis and Ureibacillus thermosphaericus to detoxify a hardwood hemicelluloses hydrolysate and enable acetone–butanol–ethanol fermentation leading to butanol

Butanol, a fuel with better characteristics than ethanol, can be produced via acetone–butanol–ethanol (ABE) fermentation using lignocellulosic biomass as a carbon source. However, many inhibitors present in the hydrolysate limit the yield of the fermentation process. In this work, a detoxification technology combining flocculation and biodetoxification within a bacterial co-culture composed of Ureibacillus thermosphaericus and Cupriavidus taiwanensis is presented for the first time. Co-culture-based strategies to detoxify filtered and unfiltered hydrolysates have been investigated. The best results of detoxification were obtained for a two-step approach combining flocculation to biodetoxification. This sequential process led to a final phenolic compounds concentration of 1.4 g/L, a value close to the minimum inhibitory level observed for flocculated hydrolysate (1.1 g/L). The generated hydrolysate was then fermented with Clostridium acetobutylicum ATCC 824 for 120 h. A final butanol production of 8 g/L was obtained, although the detoxified hydrolysate was diluted to reach 0.3 g/L of phenolics to ensure noninhibitory conditions. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2753, 2019.     

Visualization of the adsorption of a bacterial endo-β-1,4-glucanase and its isolated cellulose-binding domain to crystalline cellulose

Endo-β-1,4-glucanase A (CenA), a cellulase from the bacterium Cellulomonas fimi, is composed of two domains: a catalytic domain and a cellulose-binding domain. Adsorption of CenA and its isolated cellulose-binding domain (CBD·PT_CenA) to Valonia cellulose microcrystals was examined by transmission electron microscopy using an antibody sandwich technique (CenA/CBD·PT_CenA-CenA IgG-protein A-gold conjugate). Adsorption of both CenA and CBD·PT_CenA occurred along the lengths of the microcrystals, with an apparent preference for certain crystal faces or edges. CenA or CBD·PT_CenA, but not the isolated catalytic domain, were shown to prevent the flocculation of microcrystalline bacterial cellulose. The cellulose-binding domain may assist crystalline cellulose hydrolysis in vitro by promoting substrate dispersion.     

The flocculation of wine yeasts: biochemical and morphological characteristics in Kloeckera apiculata

The floc-forming ability of flocculent strains of Kloeckera apiculata, isolated from musts, was tested for susceptibility to proteinase and sugar treatments. Three different flocculation phenotypes were discriminated by protease digestion, whereas the inhibition of flocculation by sugars distinguished two definite patterns: one mechanism of flocculation involved a galactose-specific protein and the other a broad-specificity lectin. SEM and TEM observation of the cell surface of two different Kloeckera strains revealed fine fibrils and a diffuse structure at the point of contact in one strain, and thick masses of mucus on the cell wall of the other strain.