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Biochemical Engineering Journal (v.31, #2)

Editorial Board (pp. co2).

BEJ Keywords (pp. ii).

Solid phase micro extraction fibers, calibration for use in biofilter applications by Katarina Rupar-Gadd; Mohammad Bagher Bagherpour; Göran Holmstedt; Ulrika Welander; Mehri Sanati (pp. 107-112).

The main purpose of this study is to develop a SPME calibration method suitable for use in evaluation of concentrations of hydrophobic substances in environmental samples.The analyte used in the experiments was alpha-pinene, a hydrophobic organic compound commonly found in wood, and therefore found in wood storage facilities, wood processing industries and wood based biofilters. The SPME fibres were calibrated for different concentrations of alpha-pinene at different temperatures and relative humidities. The method was used to evaluate the removal efficiency of a lab-scale biofilter.

Keywords: SPME; Biofilters; Alpha-pinene; Bioprocess monitoring; Mass transfer; Absorption

Effects of organic chemicals on growth of Methylosinus trichosporium OB3b by Xin-Hui Xing; Hao Wu; Ming-Fang Luo; Bang-Peng Wang (pp. 113-117).

Effects of organic chemicals on the growth rate and cell density of Methylosinus trichosporium OB3b, a type II methanotroph, were studied. The examined organic chemicals were vitamins, amino acids and organic acids, including folic acid, riboflavin, tetrahydrofuran, cysteine, tyrosine, glycine, pyruvic acid, malate, maleic acid, and citrate. The results showed that M. trichosporium OB3b could not utilize the added organics as the sole carbon source for cell growth without the presence of methane. Riboflavin and organic acids such as malate, citrate, succinate and maleate could obviously improve the cell concentration of this strain. Among them, citrate exhibited the most significant effect on cell growth enhancement. When citrate was added at an optimal concentration of 0.015mmol/L, the maximal cell concentration could reach 0.75g dry cell weight/L, about 3.5 times that of the control without citrate addition. Furthermore, the improvement of the cell growth of M. trichosporium OB3b by the addition of citrate was confirmed in a bioreactor with a continuous supply of air and methane.

Keywords: Citrate; Cell growth; Methane; Methane oxidation; Methylosinus trichosporium; OB3b; Organic chemicals

Combined biological and chemical degradation for treating a mature municipal landfill leachate by Claudio Di Iaconi; Roberto Ramadori; Antonio Lopez (pp. 118-124).

The paper reports the results of a laboratory scale investigation aimed at evaluating the effectiveness of mature municipal landfill leachate treatment by a biological stage, carried out in a periodic biofilter with granular biomass (SBBGR), followed by a chemical oxidation step, performed using ozone or Fenton, for further COD removal. The results show that the biological treatment was able to remove roughly 80% of COD in leachate at an organic loading approximately equal to 1.1kgCOD/(m³day). Ammonia removal efficiency was very low (lower than 20%) because of the presence of high salinity and inhibitory compounds. When the leachate was pre-treated in order to reduce considerably the ammonia content, it was found to be possible to reach organic loadings as high as 4.5kgCOD/m³day with a decrease in COD removal of only 10%. The biological treatment was characterised by a negligible sludge production. Ozone and Fenton reagent were used to reduce the remaining COD content presumably made up of recalcitrant compounds. The treatment with ozone was able to remove only 33% of residual COD whereas using Fenton reagent an 85% removal efficiency of COD was achieved.

Keywords: Landfill leachate treatment; Periodic biofilter; Aerobic granulation; Fenton treatment; Ozonation

Mathematical model for stepwise hydrolysis of triolein using Candida rugosa lipase in biphasic oil–water system by Heri Hermansyah; Masaki Kubo; Naomi Shibasaki-Kitakawa; Toshikuni Yonemoto (pp. 125-132).

A mathematical model describing the triglyceride hydrolysis with lipase was constructed. The stepwise hydrolysis at the oil–water interface based on the Ping Pong Bi Bi mechanism and the inhibition by a fatty acid were considered in addition to the differences in the interfacial and bulk concentrations of the enzyme, substrate and product. This model was applied to the experimental results for the triolein hydrolysis using Candida rugosa lipase in the biphasic oil–water system under various operating conditions. In order to discuss the model's advantages, other simple models not considering the inhibition by a fatty acid or Ping Pong Bi Bi mechanism were also applied to our experimental results. The present model gave better fitted results and well described the effect of the initial enzyme concentration, the interfacial area and the initial concentrations of triolein and a fatty acid on the entire process of the stepwise triolein hydrolysis. The present model was very effective for predicting the appropriate conditions for the efficient production of the desired product and to provide information which cannot be experimentally obtained.

Keywords: Biphasic oil–water system; Inhibition by fatty acid; Lipase; Modelling; Ping Pong Bi Bi mechanism; Triglyceride hydrolysis

Growth kinetics of Pseudomonas putida in the biodegradation of single and mixed phenol and sodium salicylate by Ruey-Shin Juang; Shang-Yuan Tsai (pp. 133-140).

The kinetics of biodegradation of single phenol and sodium salicylate (SA) and their binary mixtures in water by suspended Pseudomonas putida CCRC 14365 was studied at 30°C and pH 7.0. Experiments were performed at different total substrate concentrations (0–4.25mM) and/or mole fractions of phenol. The initial cell concentration was fixed at 0.025g/L. Based on the parameters of the Haldane model for specific growth rate of the cells on single phenol and SA (correlation coefficient R²>0.9737), phenol had larger degradation rate than SA, whereas the inhibition of P. putida by phenol was less significant than by SA. That is, the cells were more favored to degrade phenol than SA under comparable conditions. On the other hand, the specific growth rate of the cells on binary substrates could be described by an extended Haldane equation ( R²=0.9256). The substrate interactions were thus discussed according to the modeled parameters. The dynamics in the biodegradation of single and binary substrate systems was finally analyzed.

Keywords: Growth kinetics; Pseudomonas putida; Biodegradation; Phenol; Sodium salicylate; Binary substrates

Biodegradation of 4-CP and 2,4-DCP mixture in a rotating biological contactor (RBC) by Erkan Sahinkaya; Filiz B. Dilek (pp. 141-147).

In this study, the performance of a two stage rotating biological contactor (RBC) was evaluated for the treatment of synthetic wastewater containing peptone, 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) at 5rpm. Also, the effect of biogenic substrate (peptone) concentration on the reactor performance was investigated. High chlorophenols (>98%) and COD (>94%) removals were achieved throughout the reactor operation in the first stage and the second stage behaved as a polishing step. The observed maximum 4-CP and 2,4-DCP removal rates in the first stage were 2305mg/Lday (18.3g/m²day) and 1202mg/Lday (9.5g/m²day), respectively. Deacclimation of biomass was carried out for 3.5 months after 260 days of operation with the reactor feed turning on to contain peptone only. Upon addition of 4-CP (200mg/L) and 2,4-DCP (100mg/L), a rapid reacclimation of biomass was observed within 16 days. Shock loading experiments with 4-CP (822.7±1.4) and 2,4-DCP (424.6±1.9mg/L) resulted in around four times higher effluent 4-CP concentrations than 2,4-DCP in both stages, which may be due to strong competitive inhibition of 2,4-DCP on 4-CP degradation.

Keywords: 4-Chlorophenol; 2,4-Dichlorophenol; Rotating biological contactor

Anaerobic reduction of sulfate in immobilized cell bioreactors, using a microbial culture originated from an oil reservoir by V. Baskaran; M. Nemati (pp. 148-159).

The kinetics of anaerobic sulfate reduction was studied in continuous immobilized cell bioreactors, using a consortium of sulfate reducing bacteria (SRB) enriched from the produced water of a Canadian oil reservoir. The effects of carrier matrix, concentration of sulfate in the feed and sulfate volumetric loading rate were investigated. The bioreactor performance, as assessed by volumetric reduction rate of sulfate, was dependent on the total surface area provided by the immobilization carrier matrix. Among the three tested matrices, sand displayed a superior performance with a maximum reduction rate of 1.7g/Lh was achieved at the shortest residence time of 0.5h. This reduction rate was 8- and 40-fold faster than those obtained with biomass support particles (0.2g/Lh; residence time: 5.3h) and glass beads (0.04g/Lh; residence time: 28.6h), respectively. Further kinetics studies with sand as a carrier matrix indicated that the extent of sulfate reduction rate was dependent on the feed sulfate concentration and volumetric loading rate of sulfate. At a constant feed sulfate concentration, increases in sulfate volumetric loading rate caused the reduction rate to pass through a maximum. Contrary to the pattern reported for the freely suspended SRB cells, the increases in feed sulfate concentrations led to lower reaction rates in the immobilized cell bioreactors. The maximum volumetric reduction rate with feed sulfate concentrations of 1, 2.5 and 5g/L were 1.7, 0.8 and 0.7g/Lh, observed at residence times of 0.5, 2.7 and 2.7h, respectively. The SRB consortium used in this study was dominated by incomplete oxidizers. The experimental data for lactate utilization and acetate production rates were in close agreement with those calculated based on the stoichiometry of the involved reactions.

Keywords: Acid mine drainage; Anaerobic processes; Sulfate reducing bacteria; Immobilized cells; Biokinetics; Packed-bed bioreactor

Study on the equilibrium, kinetics and isotherm of biosorption of lead ions onto pretreated chemically modified orange peel by Zhexian Xuan; Yanru Tang; Xiaomin Li; Yinghui Liu; Fang Luo (pp. 160-164).

In this paper, preparation of a new biosorbent using chemically modified orange peel and its biosorption of lead ion was studied. Effects of alkaline saponification, different concentrations of citric acid and different temperatures on the preparation of biosorbents were investigated. The influences of pH, shaking time, s/l ratio on the biosorption of lead ion by using different biosorbents were also studied. As can be seen from the experimental results that biosorption equilibriums were rapidly established in about one h and the reaction could be explained as pseudo-first-order kinetic processes. The lead adsorption was strictly pH dependent, and maximum uptakes of lead on different biosorbents were observed at pH range of 4.5–6.0. The order of maximum uptake capacity of lead ion on different biosorbents was 0.6SCA₈>0.6SCA₅>0.6SCA₂>0.1SCA₈>0.1SCA₅>0.1SCA₂>SOP>0.1CA>AOP>0.6CA>OP. The maximum adsorption capacity of lead was obtained as 1.22molkg⁻¹.

Keywords: Equilibrium; Kinetics; Isotherm; Orange peel; Biosorption; Lead ion

Effect of operating conditions on long-term performance of a biofilter treating gaseous toluene: Biomass accumulation and stable-run time estimation by Jinying Xi; Hong-Ying Hu; Yi Qian (pp. 165-172).

To achieve a stable performance during long-term operation of biofiltration process, the effect and control of excess biomass accumulation should be investigated in detail. In this study, a biofilter treating gaseous toluene was operated continuously under different operating conditions for more than 270 days. Decrease in toluene removal efficiency and increase in pressure drops of the filter bed were simultaneously observed during the operation period due to excess biomass accumulation. The distributions of toluene concentration and gas pressure suggested that more biomass would accumulate in the inlet section. By carbon balance analysis, the variation of the biomass concentration in the biofilter was calculated. The variation of the biofilter performance and the biomass concentration demonstrated that 10,000gCm⁻³ might be a critical biomass concentration for the biofilter to maintain a stable operation. An evaluation equation based on biomass growth kinetics was successfully established and used to estimate the stable-run time of a biofilter under different VOCs loadings. Bed mixing was found to be able to remove approximately 4000gVSSm⁻³ of excess biomass and could also recover the performance of the biofilter.

Keywords: VOCs; Biofilters; Biomass accumulation; Toluene gas; Bed mixing

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Biochemical Engineering Journal (v.31, #2)