Biochemical Engineering Journal (v.31, #3)
Editorial Board (CO2).
BEJ Keywords (IV).
Correlation of TCE cometabolism with growth characteristics on aromatic substrates in toluene-degrading bacteria by Yuki Morono; Hajime Unno; Katsutoshi Hori (173-179).
We have constructed a bacterial library consisting of 97 strains of toluene-degrading bacteria from soil and activated sludge samples for examining their physiological properties in terms of cometabolism of TCE. Large variation of TCE degradation ability was observed in Gram-positive and Gram-negative strains, as well as diverse patterns of availability of aromatics as a growth substrate. No clear correlation was observed between the number of available substrates for growth and TCE degradation ability. However, the growth on some of the aromatics showed positive or negative correlations with TCE degradation ability. Kendall correlation constants (tau) for the growth on cumene, m-xylene, p-xylene, and m-cresol with TCE degradation ability were statistically significant (P < 0.001): their values were −0.44, −0.31, −0.26, 0.37, respectively. Among 12 of aromatics, only m-cresol showed positive correlation with TCE degradation ability. These findings would be useful for enrichment and isolation of the microbes that have TCE-cometabolism ability, which is a selective disadvantage through the toxicity or competitive inhibition against growth substrates.
Keywords: Trichloroethylene (TCE); Biodegradation; Cometabolism; Aromatic compounds; Kendall correlation constants (tau); m-Cresol; Toluene-degrading bacteria; Substrate range;
Olive mill wastewater remediation by means of Pleurotus ostreatus by Giuseppe Olivieri; Antonio Marzocchella; Piero Salatino; Paola Giardina; Giovanna Cennamo; Giovanni Sannia (180-187).
Results of a research program on raw olive-mill wastewater (OMW) bioremediation are presented. Bioremediation experiments have been carried out both in an airlift bioreactor and in aerated flasks, using Pleurotus ostreatus. The process was investigated under controlled non-sterile operating conditions, representative of industrial operation. Growth of P. ostreatus as well as polyphenols conversion were assessed. OMW bioconversion was characterized in terms of total organic carbon, polyphenols concentration, phenol oxidase activity, extent of decolourization and pH as a function of time. Results demonstrate that: P. ostreatus effectively grows on raw OMW; polyphenols abatement is controlled by the availability of nutrients and can be as large as 95%; bioconversion of non-sterilized OMW does not result into appreciable decolourization of the liquid medium. The use of an internal loop airlift bioreactor as a candidate for the full-scale implementation of an OMW aerobic bioremediation process is demonstrated.
Keywords: Olive mill wastewater; Airlift; Polyphenols; Laccase; Bioremedation; Pleurotus ostreatus;
Gas–liquid mass transfer in an up-flow cocurrent packed-bed biofilm reactor by Julio Pérez; José Luis Montesinos; Francesc Gòdia (188-196).
Gas–liquid mass transfer was investigated in an up-flow cocurrent packed-bed biofilm reactor. In aerobic processes gas–liquid mass transfer can be considered as a key operational parameter as well as in reactor scale-up. The present paper investigates the influence of the liquid phase mixing in the determination of the volumetric gas–liquid mass transfer coefficient (k L a) coefficient. Residence time distribution (RTD) experiments were performed in the reactor to determine the flow pattern of the liquid phase and to model mathematically the liquid phase mixing. The mathematical model derived from RTD experiments was used to evaluate the influence of the liquid mixing on the experimental estimation of the (k L a) in this reactor type. The methods used to estimate the k L a coefficient were: (i) dynamic gassing-out, (ii) sulphite method, and (iii) in-process estimation through biological conversion obtained in the reactor. The use of standard chemical engineering correlations to determine the k L a in this type of bioreactors is assessed. Experimental and modelling results show how relevant can be to take into consideration the liquid phase mixing in the calculations of the most-used methods for the estimation of k L a coefficient. k L a coefficient was found to be strongly heterogeneous along the reactor vertical axis. The value of the k L a coefficient for the packed-bed section ranged 0.01–0.12 s−1. A preliminary correlation was established for up-flow cocurrent packed-bed biofilm reactors as a function of gas superficial velocity.
Keywords: Gas–liquid mass transfer; Biofilm reactor; Packed-bed bioreactors; Nitrification; Mathematical modelling; Flow model;
Biosorption kinetics and isotherm studies of Acid Red 57 by dried Cephalosporium aphidicola cells from aqueous solutions by Ismail Kiran; Tamer Akar; A. Safa Ozcan; Adnan Ozcan; Sibel Tunali (197-203).
Equilibrium, kinetics and thermodynamic studies on the removal of Acid Red 57 (AR57) by biosorption onto dried Cephalosporium aphidicola (C. aphidicola) cells have been investigated in a batch system with respect to pH, contact time and temperature. The results showed that the equilibrium time was attained within 40 min and the maximum biosorption capacity of AR57 dye onto C. aphidicola cells was 2.08 × 10−4 mol g−1 or 109.41 mg g−1 obtained after contact with 0.4 g dm−3 biosorbent concentration, pH0 of 1 and at a temperature of 20 °C. The pseudo-second-order kinetic model was observed to provide the best correlation of the experimental data among the kinetic models studied. Biosorption isotherm models were developed and the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models were conformed well to the experimental data. The changes of free energy, enthalpy and entropy of biosorption were also evaluated for the biosorption of AR57 dye onto C. aphidicola cells.
Keywords: Cephalosporium aphidicola; Biosorption; AR57; Isotherms; Kinetics;
Equilibrium and kinetic studies on sorption of basic dyes by a natural biopolymer poly(γ-glutamic acid) by B. Stephen Inbaraj; J.T. Chien; G.H. Ho; J. Yang; B.H. Chen (204-215).
A bacteria-derived biodegradable and non-toxic biopolymer poly(γ-glutamic acid) (γ-PGA) was evaluated as an adsorbent for removal of basic dyes from aqueous solution. Sorption experiments were carried out with three basic dyes Auramine O (Au–O), Rhodamine B (Rh–B) and Safranin O (Sa–O) by a batch mode at different initial dye concentrations, agitation times, γ-PGA doses, temperatures, pH and added salts. Sorption isotherms were well described by the Redlich–Peterson equation, closely followed by Sips, when compared to Freundich and Langmuir models. The maximum sorption capacity derived from Langmuir model at 301 K was 277.29, 390.25 and 502.83 mg/g for Au–O, Rh–B and Sa–O dyes, respectively. The kinetics of dyes sorption on γ-PGA followed a pseudo second order equation and the rate was controlled by chemical sorption. An ion-exchange model assuming adsorption to be a chemical phenomenon also predicted the kinetic data precisely. Thermodynamic parameters (ΔH°, ΔS° and ΔG°) obtained revealed dye sorption to be an exothermic and spontaneous process with decreasing randomness of dyes at the solid/solution interface. Dye sorption increased with increase in solution pH and reached a plateau at pH 5, while desorption of about 98% of dyes from spent γ-PGA occurred at pH 1. The incorporation of salts decreased the dye sorption, suggesting the binding of dyes on γ-PGA may involve ion-exchange mechanism.
Keywords: Adsorption; Poly(γ-glutamic acid); Polypeptide; Basic dyes; Modelling; Kinetic parameters; Isotherm parameters;
Hexavalent chromium removal from aqueous solution by adsorption on treated sawdust by Saroj S. Baral; Surendra N. Das; Pradip Rath (216-222).
The studies on adsorption of hexavalent chromium were conducted by varying various parameters such as contact time, pH, amount of adsorbent, concentration of adsorbate and temperature. The kinetics of adsorption of Cr(VI) ion followed pseudo second order. Langmuir adsorption isotherm was employed in order to evaluate the optimum adsorption capacity of the adsorbent. The adsorption capacity was found to be pH dependant. Sawdust was found to be very effective and reached equilibrium in 3 h (adsorbate concentration 30 mg l−1). The rate constant has been calculated at 303, 308, 313 and 318 K and the activation energy (E a) was calculated using the Arrhenius equation. Thermodynamic parameters such as standard Gibbs energy (ΔG°) and heat of adsorption (ΔH r) were calculated. The ΔG° and ΔH r values for Cr(VI) adsorption on the sawdust showed the process to be exothermic in nature. The percentage of adsorption increased with decrease in pH and showed maximum removal of Cr(VI) in the pH range 4.5–6.5 for an initial concentration of 5 mg l−1.
Keywords: Adsorption; Cr(VI); Treated sawdust; Kinetics; Isotherm and thermodynamics;
High rate aerobic treatment of synthetic wastewater using enhanced coagulation high-performance compact reactor (EC-HCR) by Chen Zhiqiang; Wen Qinxue; Wang Jianlong (223-227).
The high-performance compact reactor (HCR) is a type of JLR system for wastewater aerobic biological treatment processes. HCR has demonstrated outstanding performance with respect to space–time yield in more than 20 industrial applications, whereas, it has the disadvantage of cloudy effluent because of the disappearance of filamentous organisms in the HCR reactor. This study examined the potential of a new enhanced coagulation HCR (EC-HCR) system to improve the effluent quality of HCR. Results showed that, when 20–25 mg/L FeCl3 was added as coagulant into the coagulation tank, the effluent turbidity of EC-HCR system was lower. EC-HCR system could be operated at high organic loading and had high COD removal efficiency under short hydraulic retention time. When influent COD varied at 300–450 and 500–650 mg/L, there was no obvious difference on effluent COD compared with and without coagulant added. When influent with high COD concentration of 1000–1600 mg/L was treated, the COD removal efficiency could be improved obviously when 20 mg/L coagulant was added. There was no obvious difference between the nitrogen concentration in the effluent with and without coagulant, whereas, the phosphorus removal efficiency improved markedly when 20 mg/L coagulant was added into coagulation tank.
Keywords: High-performance compact reactor (HCR); Enhanced coagulation HCR (EC-HCR); Coagulant; Turbidity; COD; Nitrogen; Phosphorus;
Release characteristics of three model drugs from chitosan/cellulose acetate multimicrospheres by Hui Yun Zhou; Xi Guang Chen; Cheng Sheng Liu; Xiang Hong Meng; Chen Guang Liu; Le Jun Yu (228-233).
Chitosan/cellulose acetate multimicrospheres (CCAM) loaded different model drugs were prepared by the method of w/o/w emulsion. Model drugs with different hydrophilicity were selected to investigate the delivery system, such as hydrophilic ranitidine hydrochloride (RT), amphoteric acetaminophen (ACP) and hydrophobic 6-mercaptopurine (6-MP). The size of CCAM loaded RT or ACP were almost the same of 200–280 μm and the size of CCAM loaded 6-MP was only 50–80 μm. With the increasing of hydrophobicity of drug, the holes in the appearance of microspheres became smaller and the loading efficiency increased. The loading efficiency of 6-MP was more than 30% whereas that of RT and ACP was only 10%. The CCAM system had good effect on the controlled release in vitro of all model drugs of different hydrophobicity. However, the release rate was affected by the hydrophobicity of model drug. It became slower with the increasing of hydrophobicity of drugs. The highest release rate was almost 60% during 48 h which was for the hydrophilic drug of RT and the release rate of hydrophobic drug (6-MP) was not more than 30% in the same time.
Keywords: Cellulose acetate; Chitosan; Multimicrosphere; Controlled release in vitro; Hydrophilic and hydrophobic;
Astaxanthin biosynthesis from simultaneous N and P uptake by the green alga Haematococcus pluvialis in primary-treated wastewater by Chang Duk Kang; Jin Young An; Tai Hyun Park; Sang Jun Sim (234-238).
An alternative microalgal system for biological wastewater treatment is proposed for both the removal of nitrogen and phosphorus from wastewater and the production of a valuable carotenoid, astaxanthin. The system consists of sequential photoautotrophic cultivation and induction processes using the green alga Haematococcus pluvialis. The Haematococcus process was applied to primary-treated sewage (PTS) and primary-treated piggery wastewater (PTP) with serial dilution. H. pluvialis grew well on PTS and PTP diluted four-fold, resulting in the successful removal of nitrogen and phosphorus from both wastewaters. At that time, cell growth rates were comparable to those in the algal-defined NIES-C medium. Following the cultivation stage, N-deprived vegetative cells were transformed under photoautotrophic induction by continuous feeding of both CO2-mixed gas and intense light to red aplanospores with substantial astaxanthin contents. The resulting astaxanthin contents accounted for about 5.1 and 5.9% of the total biomass of the PTS and PTP cultures, respectively. Our results indicate the potential of the proposed Haematococcus process as a subsidiary wastewater treatment technology with the capability of biosynthesizing the high-value antioxidant astaxanthin.
Keywords: Wastewater treatment; Haematococcus pluvialis; Astaxanthin; Photoautotrophic induction; Carotenoid production; Microalgae;