Biochemical Engineering Journal (v.34, #1)

A bubble column and a novel airlift reactor with divided draft tubes were used for the cultivation of aerobic granules at the superficial air velocity of 1.2 cm s−1. It was found that profiles of biomass concentration, average particle size and SVI of biomass showed the same changing trends during the first 40-day operation in the bubble column and the airlift reactor. After 60-day operation, the biomass concentration, average particle size, and SVI of biomass reached 4.5 g l−1, 1300 μm and 30 ml g−1, respectively, and then maintained at these values during the next 3-month operation in airlift reactor. However, morphology of granular sludge in bubble column changed at day of 50 and then disintegrated into bioflocs at day of 67 when biomass concentration reached to 8.0 g l−1, which led to the great increase of SVI of biomass and the wash-out of lots of biomass from reactor. Clear and regular granules were seen again at day of 75 and granules gradually grew to bigger sizes. But the system deterioration happened again when biomass in bubble column increased to about 8.0 g l−1. It was found that DO concentration in feast period was about 35–40% with biomass concentration of 8.0 g l−1 in bubble column while DO concentration was above 60% with biomass concentration of 4.5 g l−1 in airlift reactor. Thus, it was thought that lower oxygen concentration due to higher biomass concentration was mainly the reason of unstable operation of aerobic granules in bubble column at superficial air velocity of 1.2 cm s−1.
Keywords: Aerobic granules; Bubble column; Airlift reactor; Aeration rate; Stability; DO concentration;

Penicillium lilacinum dextranase was immobilized covalently onto Eupergit C and was used for the production of isomaltooligosaccharides. Immobilization resulted in 90% relative activity. The immobilized enzyme showed no decrease in activity for 20 batch reactions. Optimum conditions were not affected by immobilization, and optimum pH and temperature for free and immobilized enzyme were 4.5–5.5 and 30–35 °C, respectively. Immobilized enzyme was more stable at low and high pH and high temperatures. The kinetic parameters for the free and immobilized enzyme were also determined. The immobilized enzyme could be used for the production of isomaltooligosaccharides, since the immobilization efficiency is high (90%) and immobilized enzyme retains its activity for 20 days without any decrease.
Keywords: Immobilization; Penicillium lilacinum; Dextranase; Eupergit C; Isomaltooligosaccharides;

Candida rugosa lipase was immobilized by covalent binding on wood cellulignin (Eucaliptus grandis) chemically modified with different activating agents as carbonyldiimidazole, glutaraldehyde and sodium metaperiodate. The resulted immobilized derivatives were evaluated in both aqueous (hydrolysis) and organic (ester synthesis) media. In aqueous media a comparative study between free and immobilized derivatives was provided in terms of pH, temperature and kinetic constants (V max and K m) following the hydrolysis of p-nitrophenyl palmitate, in which new optima values were established. The experimental results suggested that functional activating agents render different interactions between enzyme and cellulignin, producing consequently alterations in the optimal reaction conditions. Different behavior was found when the immobilized derivatives were tested in organic media, under these conditions similar esterification activities were observed, independent on the agent used to active the immobilizing support. Reasons for this are discussed on the light of the interactions among the support, functional activating agent and lipase structure.
Keywords: Candida rugosa lipase; Cellulignin; Functional activating reagent; Immobilization;

Thermal pre-treatments can be used in order to enhance the efficiency of anaerobic digestion of waste activated sludge. The objective of this work was to study the effects of thermal treatment on the semi-continuous anaerobic digestion of the main sludge compounds (proteins, carbohydrates and lipids). Thermal treatment at 190 °C was more efficient than treatment at 135 °C in terms of total COD, lipids, carbohydrates and protein removals and methane production. However, treatment at 190 °C produced refractory soluble COD. In all cases, with or without pre-treatments, lipids degradation yield (67% without pre-treatment and 84% with 190 °C treatment) was higher than carbohydrates (56% without pre-treatment and 82% with 190 °C treatment) and proteins (35% without pre-treatment and 46% with 190 °C treatment) degradation yields. Methane production increased by 25% after the 190 °C treatment. This moderate enhancement could be explained by a good initial biodegradability of tested sludge and by the sludge storage which was done for a long period. Enzymatic reactions may occur even at 4 °C. However, this methane production enhancement was enough to produce energy to pre-heat the sludge.
Keywords: Thermal treatment; Anaerobic processes; Biogas; Waste treatment; Proteins; Carbohydrates; Lipids;

l-Amino acyl (14) esters of carbohydrates (515) were synthesized through Candida rugosa lipase catalysis in non-polar solvent with yields in the range of 7–79%. In a reaction, involving unprotected and unactivated l-amino acids and carbohydrates, both monoesters (1-O-, 2-O-, 3-O-, 4-O-, 5-O-, 6-O- and 6′-O-) and diesters (1,6-di-O-, 2,5-di-O-, 2,6-di-O-, 3,6-di-O-, 4,6-di-O- and 6,6′-di-O-) were found to be formed in different proportions depending on the l-amino acids and carbohydrates employed. Among 80 individual esters synthesized by this procedure, 67 are being reported for the first time.
Keywords: Amino acyl esters of carbohydrates; Candida rugosa lipase; Monoesters; Diesters; Unprotected amino acids;

A β-cyclodextrin glycosyltransferase from a newly isolated Paenibacillus pabuli US132 strain: Purification, properties and potential use in bread-making by Sonia Jemli; Ezzedine Ben Messaoud; Dorra Ayadi-Zouari; Belgacem Naili; Bassem Khemakhem; Samir Bejar (44-50).
A bacterial strain designed US132, isolated from a Tunisian soil was selected for its production of a potent cyclodextrin glycosyltransferase (CGTase) activity. This strain was identified as Paenibacillus pabuli by sequencing of the 16S rDNA and the 16S-23S internal transcribed spacer (ITS). The US132 CGTase, purified to homogeneity by hydrophobic interaction chromatography and starch adsorption, is a monomer of approximately 70 kDa. This enzyme exhibited a maximal activity at 65 °C, in presence of 10 mM calcium, and was most active at pH range 5.5–9 with an optimum at 6.5. Using 10% (w/v) of potato starch, this CGTase produced a high level of cyclodextrins reaching 42 g/l with a β-cyclodextrin ratio of 63%. Furthermore, this enzyme can be used in the bread-baking process since its addition in the dough mix improved significantly the loaf volume and decreased the firmness of bread during storage.
Keywords: β-CGTase; Paenibacillus pabuli; Purification; Cyclodextrins production; Bread-making;

Influence of industrial discharges on the performance and population of a biological nutrient removal process by A. De Lucas; L. Rodríguez; J. Villaseñor; F.J. Fernández (51-61).
The study described here concerns the influence of long-term industrial discharges on a biological nutrient removal process. The effects of such discharges were modeled and the effect on the effluent quality and on the population of activated sludge was evaluated. The influent wastewaters used, i.e., urban sewage and industrial discharges, were real wastewaters. A model of the process involving GAO integrated into ASM2d was used for the simulations. For the simulation of the industrial discharges only two parameters needed to be changed and these were the maximum fermentation rate (q fe) and the reduction factor for anoxic activity of PAO ( η N O 3 ) . These changes could be explained in terms of the high biodegradability and the absence of toxic compounds in the studied wastewaters. The industrial discharges were found to have either a positive or negative impact on the nutrient and COD removal. The level of impact was found to depend on the characteristics of the discharge—mainly the VFA, the nitrogen content and the P/COD ratio.
Keywords: Bioreactors; Activated sludge; Modeling; Waste-water treatment; Biological nutrient removal; Environmental preservation;

Neural fuzzy modeling of ethanolamine pulping of vine shoots by L. Jiménez; V. Angulo; S. Caparrós; A. Pérez; J.L. Ferrer (62-68).
The influence of operational variables in the pulping of vine shoots by use of ethanolamine [viz. temperature (155 to 185 °C), cooking time (30 to 90 min) and ethanolamine concentration (50 to 70%, v/v)] on the properties of the resulting pulp (viz. yield, kappa index and viscosity) and paper sheets (breaking length, stretch, burst index, tear index and brightness) was studied.A central composite factorial design was used in conjunction with the software ANFIS Edit Matlab 6.5 to develop fuzzy neural model that reproduced the experimental results of the dependent variables with errors less than 10%. The model is therefore effective with a view to simulating the ethanolamine pulping process.
Keywords: Vine shoots; Pulping; Pulp; Paper; Ethanolamine; Neural fuzzy modelling;

Chromium(VI) removal by calcined bauxite by Saroj S. Baral; Surendra N. Das; Pradip Rath; Gautam R. Chaudhury (69-75).
The present paper deals with the efficiency of treated bauxite to remove Cr(VI) from a synthetic solution. It includes adsorption of Cr(VI) as a function of contact time, particle size, adsorbent dosage, temperature and initial concentration of the synthetic solution. The treated bauxite (1 g/25 mL) is found to be capable of removing up to 98% of Cr(VI) from solution having low initial concentration (10 mg/L). The adsorption is highest at 45 °C and rate of adsorption is very slow after 5 min. The adsorption isotherm follows both the Langmuir and Freundlich isotherm. The change in the lattice structure of adsorbent before and after calcinations was analyzed by XRD, FTIR and SEM analysis. The thermodynamic and kinetic parameter such as Gibbs free energy, isosteric heat of adsorption and rate constant were calculated.
Keywords: Calcined bauxite; Adsorption; Cr(VI) removal; Isotherm; Kinetics; XRD; FTIR; SEM;

Poly(methacrylate-co-ethylene dimethacrylate) monolithic column (100 mm × 4.6 mm i.d.) subsequently modified with DEAE-dextran had been prepared for the separation of proteins with anion-exchange mode. The column, which possessed the specific surface area of 5.3 m2/g and immobilized amine group of 9.93 μmol/g media, showed even better permeability of 607 psi at flow rate of 1445 cm/h in comparison to diethylamine modification procedure. The dynamic binding capacity of bovine serum albumin (BSA) was 23.8 mg/g media. Fast separation of lysozyme, hemoglobin and BSA on the column was achieved within 3 min at flow rate of 1445 cm/h.
Keywords: Monolithic column; DEAE-dextran; Protein; Separation;

This research aimed at optimizing fermentation condition (initial pH and temperature) of xylanase production from Penicillium oxalicum ZH-30 by statistical analysis using response surface methodology. Statistical analysis of results showed that the linear, quadric terms and interaction of these two variables had significant effects. The optimal conditions for higher production of xylanase were: initial pH 7.38 and temperature = 31.1 °C. The predicted and verified xylanase activities under optimal condition were 14.33 and 14.50 U/mL, respectively. The temperature range suitable for the industrial application of xylanase from P. oxalicum ZH-30 was 50–60 °C.
Keywords: Penicillium oxalicum ZH-30; Optimization; Response surface methodology; Xylanase;

Rheological properties of anaerobic hydrogen-producing flocs by Yang Mu; Xi-Hua Chen; Han-Qing Yu (87-91).
The rheological characteristics of anaerobic hydrogen-producing flocs were investigated in this study. The Sisko model was employed to describe the rheology of hydrogen-producing flocs and determine their limiting viscosity. In addition, the effects of sludge concentration, temperature, and pH on the floc limiting viscosity were evaluated. Experimental results indicated that the hydrogen-producing flocs showed shear-thinning behavior. The Sisko model was found to be able to adequately describe the rheology of the hydrogen-producing flocs. The relationships between the limiting viscosity of the flocs with the solids content and the limiting viscosity with temperature could be, respectively, modeled by an exponential equation and Arrhenius equation very well. The limiting viscosity of the flocs seemed not to be sensitive to changes of solution pH.
Keywords: Anaerobic; Hydrogen-producing flocs; Model; Rheological properties;

Partitioning of model proteins in aqueous two-phase systems containing polyethylene glycol and ammonium carbamate by Natália Luiza Penna Dallora; João Gabriel Degam Klemz; Pedro de Alcântara Pessôa Filho (92-97).
The phase equilibrium and the partitioning of bovine serum albumin, trypsin and lysozyme in aqueous two-phase systems containing ammonium carbamate and polyethylene glycol 1500, 4000 and 6000 are presented in this communication. Partition coefficients, defined as the ratio of protein concentration in the polymer phase to that in the salt phase, vary in the range of 0.1–0.8 for bovine serum albumin, 1.0–2.4 for trypsin and from 2.3 to 9.0 for lysozyme, depending on the polymer chain size and on the tie-line length. The analysis of the separation factor, defined as the ratio of partition coefficients of two proteins, shows that high degrees of separation can be achieved. These results indicate that aqueous two-phase systems containing ammonium carbamate and polyethylene glycol can be an alternative to be considered for protein downstream processing.
Keywords: Protein; Downstream processing; Aqueous two-phase systems; Salt; Polymer;