Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Biochemical Engineering Journal (v.51, #1-2)
Effect of substrate concentration, pH, and temperature on the activity of the complex glucose–fructose oxidoreductase/glucono-δ-lactonase present in calcium alginate-immobilized Zymomonas mobilis cells by Eloane Malvessi; Sabrina Carra; Mauricio Moura da Silveira; Marco Antônio Záchia Ayub (pp. 1-6).
The action of the enzymes glucose–fructose oxidoreductase (GFOR) and glucono-δ-lactonase (GL), present in calcium alginate-immobilized Zymomonas mobilis cells, was characterized in relation to substrate concentration (0.05–2.0molL−1), pH (5.2–9.7), and temperature (34–59°C). Higher enzymatic activities were obtained at pH 7.8 and 8.2 and at 47 and 50°C, which were 80% higher than the conditions presented in previously defined conditions for free cells, namely at pH 6.4 and 39°C. Further analysis indicated that these findings are related to the diffusional barrier resulting from the calcium alginate beads, which hinder the transport of gluconic acid from the inner space of the beads to the external medium. This behavior was reproduced during the initial moments of bioconversion performed at pH 7.8 and 47°C. Nevertheless, during the last hours of the process, the reaction stopped because of inadequate pH levels inside the beads. The results suggest that a variable pH – from 7.8 to 6.4 – and a constant temperature of about 47°C are the best conditions for achieving good conversion yields and productivities.
Keywords: Glucose–fructose oxidoreductase/glucono-δ-lactonase; Zymomonas mobilis; Immobilized cells; Substrate concentration; pH; Temperature
Zearalenone determination in corn silage samples using an immunosensor in a continuous-flow/stopped-flow systems by Nancy V. Panini; Franco A. Bertolino; Eloy Salinas; Germán A. Messina; Julio Raba (pp. 7-13).
Zearalenone (ZEA) is a mycotoxin produced by a variety of Fusarium fungi that infects cereals. ZEA may accumulate in cereals before harvest time. This paper describes the development of an immunosensor coupled to glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNT) (CNT-GCE) integrated with a continuous-flow systems for rapid and sensitive quantification of ZEA in corn silage samples. Mouse monoclonal anti-ZEA antibodies were immobilized on a rotating disk. The ZEA in corn sample is allowed to compete immunologically with ZEA bound to horseradish peroxidase (HRP) for the immobilized antibodies. HRP in presence of hydrogen peroxide (H2O2) catalyzes the oxidation of 4- tert-butylcatechol (4-TBC), whose back electrochemical reduction was detected on CNT-GCE at −0.15V. The total assay time was 15min. The electrochemical immunosensor showed higher sensitivity and lower detection limits than the standard ELISA method, which shows potential for detecting ZEA in foods and feeds diagnosis.
Keywords: Enzyme immunoassays; Zearalenone; Multiwall carbon nanotubes; Horseradish peroxidase; Flow injection analysis
Flocculation of diatomite by a soy protein-based bioflocculant by Hideshi Seki; Hideo Maruyama; Yasuhiro Shoji (pp. 14-18).
A novel bioflocculant, methylated soy protein (MeSP), has been developed and its flocculation performance was tested with diatomite suspensions in freshwater (pH 2–11) and in seawater. The flocculation performance of MeSP was much higher than that of commercial polyaluminum chloride (PAC) in terms of supernatant clarity and floc settling velocity. In freshwater and at a fixed flocculant dosage of 60ppm, MeSP could reduce the relative absorbance to 0.1 within 1min over a wide pH range (pH 3–10), while PAC was effective only at around pH 5. In seawater (pH 8), there was a striking difference in flocculation performance between MeSP and PAC. MeSP (20–50ppm) could reduce the relative absorbance to less than 0.1, while PAC was ineffective. The settling velocity of the floc formed by MeSP in freshwater at pH 7 and in seawater was about 4mm/s. MeSP was applied to the flocculation of a real wastewater generated from an andesite quarry. The relative absorbance could be reduced to less than 0.05 by the addition of 40ppm of MeSP. The floc settling velocity was about 5mm/s.
Keywords: Bioflocculant; Methylated protein; Soy protein; Diatomite suspension
The tolerance of Rhizopus arrihizus to U(VI) and biosorption behavior of U(VI) onto R. arrihizus by Jing-song Wang; Xin-jiang Hu; Jie Wang; Zheng-lei Bao; Shui-bo Xie; Jin-hui Yang (pp. 19-23).
This work focused on U(VI) biosorption using suspended Rhizopus arrihizus. To understand the biosorption process, the tolerance of the strain to U(VI) and the effects of solution pH, initial U(VI) concentration, temperature, and contact time on U(VI) removal were investigated in batch systems. The results demonstrated that R. arrihizus can grow normally in 200mgL−1 uranium-contained medium. Optimum biosorption was observed at solution pH 4.0 and the maximum biosorption capacity (112.2mgg−1) was obtained at initial U(VI) concentration of 200mgL−1. The biosorption process appeared to be temperature independent. Biosorption equilibrium was established within 90min and the pseudo second-order model was found to fit accurately with the experimental data. FT-IR analysis and SEM morphology indicated that the structure of the strain remained integral after biosorption. Amino group plays an important role in the biosorption process, hydroxyl and carboxyl groups are also involved in U binding.
Keywords: Biosorption; Rhizopus arrihizus; Tolerance; Uranium; Functional groups; Batch systems
Recycling of phase components during lysozyme extraction from hen egg white in the EO50PO50/K2HPO4 aqueous two-phase system by R. Dembczynski; W. Bialas; T. Jankowski (pp. 24-31).
An aqueous two-phase system (ATPS) composed of a thermoseparating copolymer EO50PO50 [50% (w/w) ethylene oxide and 50% (w/w) propylene oxide] and K2HPO4 was used to extract lysozyme from hen egg white over four successive extractions, using the recovery and recycling of phase components. Extraction was performed in two stages. In the first stage the primary two-phase system of 40% EO50PO50/10% K2HPO4 (w/w) was formed and the lysozyme partitioned to the top copolymer-rich phase while the contaminant proteins remained in the bottom phosphate-rich phase. In the next stage the copolymer-rich phase was isolated and subjected to temperature-induced phase separation. The resultant secondary two-phase system was composed of a concentrated solution of copolymer and a water solution of lysozyme. Next, the concentrated solution of EO50PO50 recovered after thermoseparation was mixed with the phosphate solution recovered from the primary system and a new portion of hen egg white added to obtain a new lysozyme extraction system. The specific activity of lysozyme preparations obtained during the four successive extractions ranged from 38,438 to 42,907U/mg of protein.
Keywords: Lysozyme; Egg white; Bioseparation; Aqueous two-phase systems; Temperature-induced phase separation; EOPO
Bio-catalyzed electrochemical treatment of real field dairy wastewater with simultaneous power generation by S. Venkata Mohan; G. Mohanakrishna; G. Velvizhi; V. Lalit Babu; P.N. Sarma (pp. 32-39).
Biologically catalyzed electrochemical treatment of real field dairy wastewater in association with power generation was studied in single chamber non-catalyzed microbial fuel cell (MFC, open-air cathode). The performance was evaluated at four organic loads employing anaerobic mixed consortia as anodic biocatalyst. Experimental data illustrated the integrated function of MFC to harness bioelectricity from the treatment of dairy wastewater. Along with good substrate degradation (chemical oxygen demand (COD), 95.49%), MFC also documented good removal of proteins (78.07%), carbohydrates (91.98%) and turbidity (99.02%). A steady increase in MFC performance was observed with increase in substrate load. Maximum volumetric power production (1.10W/m3; 308mV; 1.78mA) was observed at 4.44kgCOD/m3. MFC performance as power generator was characterized based on polarization behavior, cell potentials, cyclic voltammetric analysis and sustainable power estimation. In view of inherent advantages of the process, if optimized and understood well, this integrated approach can be a good replacement for the conventional biological and electrochemical wastewater treatment processes.
Keywords: Bio-electrochemical system; Bioelectricity; Bio-potential; Anaerobic mixed consortia; Microbial fuel cell (MFC); Bio-electrochemical treatment
Oxygen transfer in three scales of concentric tube airlift bioreactors by M.O. Cerri; A.C. Badino (pp. 40-47).
Oxygen transfer was evaluated in three internal-loop airlift reactors (ALRs) of different working volumes (2, 5, and 10dm3) and similar geometric configuration utilizing eight Newtonian and five non-Newtonian fluids. The effects of the superficial gas velocity ( U GR) and liquid viscosity ( μ L) had opposite effects on the volumetric oxygen transfer coefficient ( k L a). However, they presented the same orders of magnitude showing that the viscosity effect on oxygen mass transfer cannot be neglected. A correlation for k L a based on dimensional analysis considering the effects of the geometric parameters, the physical properties of the fluid, and the operational conditions presented a very good fitting to the experimental data. The correlation shows that the influence of the reactor internal diameter on k L a was considered positive. Therefore, in larger-scale reactors an appropriate oxygen transfer can be reached under smaller aeration conditions.
Keywords: Airlift bioreactors; Mass transfer; Hydrodynamics; Newtonian fluids; Non-Newtonian fluids; Scale-up
Hydrogen production from acetate in a cathode-on-top single-chamber microbial electrolysis cell with a mipor cathode by Kun Guo; Xinhua Tang; Zhuwei Du; Haoran Li (pp. 48-52).
A cathode-on-top single-chamber microbial electrolysis cell (MEC) was constructed by putting the cathode above the anode. The cathode was made of mipor titanium tube coated with platinum and the anode was graphite granules with exoelectrogens absorbed on its surface. Sodium acetate was used as the substrate. In 24h batch tests, when the applied voltages increased from 0.2V to 1.0V with an interval of 0.1V, the hydrogen production rates increased from 0.03L/L/d to 1.58L/L/d, and the overall hydrogen recoveries increased from 26.03% to 87.73%. The maximum overall energy recovery was 86.78% when the applied voltage was 0.6V. Meanwhile, hydrogen production was accompanied by evolution of methane, and the main methane producer in this MEC was hydrogenotrophic methanogens. The methane production rate increased with the increase of the hydrogen production rate when the applied voltage was under 0.5V; however, it maintained approximately 0.04L/L/d when the applied voltage was above 0.5V. These results demonstrate that putting the cathode above the anode is able to increase the hydrogen recoveries but also obtain high hydrogen production rates. These results also demonstrate that operating this MEC at a relative higher voltage (>0.6V) is able to reduce methane production and improve the hydrogen recovery in 24h batch tests.
Keywords: Microbial electrolysis cells; Microbial fuel cells; Biohydrogen production; Single chamber; Cathode-on-top; Acetate
Characterization of detergent stable and feather degrading serine proteases from Bacillus mojavensis A21 by Anissa Haddar; Alya Sellami-Kamoun; Nahed Fakhfakh-Zouari; Noomen Hmidet; Moncef Nasri (pp. 53-63).
The present study describes the characterization of crude protease from Bacillus mojavensis A21 and its evaluation in detergent and chicken feathers hydrolysis. The strain was found to produce at least six major extracellular proteases as shown by casein-zymography. The optimum pH and temperature for proteolytic activity were 8.0–11.0 and 60°C, respectively. The crude protease showed extreme stability towards non-ionic (5% Tween 80 and 5% Triton X-100) and anionic (1% SDS) surfactants, and relative stability towards oxidizing agents. Additionally, it showed excellent stability and compatibility with various solid (7mg/ml) and liquid (1%; v/v) detergents at temperatures from 30 to 50°C. In the presence of solid detergents, the enzyme preparation retained 100% of its initial activity after pre-incubation for 1h at 40°C with Axion and Ariel, followed by Nadhif (87%), Dixan (85%) and New Det (82%). With liquid detergents, the enzyme preparation retained 100% of its original activity after pre-incubation for 1h at 40°C with Dixan and Nadhif. Wash performance analysis revealed that A21 crude protease could effectively remove blood-stains. In addition, B. mojavensis A21 proteolytic preparation showed important feather degrading activity.Considering its promising properties, B. mojavensis A21 enzymatic preparation may be considered a potential candidate for future use in biotechnological processes, particularly in detergent and in the processing of poultry waste.
Keywords: Bacillus mojavensis; Alkaline serine proteases; Detergent stable; Keratinolytic activity
Model based control of minimal overflow metabolite in technical scale fed-batch yeast fermentation by Akif Hocalar; Mustafa Türker (pp. 64-71).
The specific growth rate should ideally be maintained at maximum oxidative growth rate in order to maximize biomass yield and productivity in fed-batch yeast fermentations. However, a more conservative approach is adopted in industry where specific growth rate is kept below the critical value to prevent the accumulation of overflow metabolite ethanol by using predetermined feeding profiles. In this work, biomass growth is maintained just above maximum oxidative growth rate by regulating ethanol concentration in the fermenter. The state feedback linearizing control strategy is developed and applied to the technical scale fed-batch yeast fermentations. The proposed control algorithm is constructed on the reliable state estimation algorithm developed previously and the biomass concentrations and ethanol measurements are then used in the control algorithm. The ethanol concentration is successfully controlled at fixed and time varying set values. By this approach the specific growth rate is controlled just over the critical value by regulating minimal ethanol concentration in order to maximize the biomass productivity.
Keywords: Nonlinear process; Feedback linearizing control; Fed-batch; Baker's yeast; Ethanol concentration; Biocalorimetry
Cellulases, xylanases, β-glucosidase and ferulic acid esterase produced by Trichoderma and Aspergillus act synergistically in the hydrolysis of sugarcane bagasse by Leda Maria Fortes Gottschalk; Raul Alves Oliveira; Elba Pinto da Silva Bon (pp. 72-78).
Trichoderma reesei and Aspergillus awamori enzymes were concentrated, pooled and assessed for the hydrolysis of steam-pretreated sugarcane bagasse. The enzyme profile of T. reesei gave (IU/L): 1700 FPA, 20,000 CMCase, 340 β-glucosidase and 12,600 xylanase. FPA and CMCase activities that were 4-fold higher than those of A. awamori (420 and 4900IU/L, respectively). However the β-glucosidase and xylanase activities were 134- and 6-fold lower than those of A. awamori (45,600 and 79,100IU/L, respectively). Furthermore, A. awamori produced ferulic acid esterase (160IU/L) which acts synergistically with cellulolytic–xylanolytic enzymes in the hydrolysis of lignocellulosic materials. The FPA and CMCase activities in the T. reesei– A. awamori blends were enhanced synergistically by 2-fold. Moreover, the hydrolytic effectiveness of the blends was superior to the use of unblended T. reesei or A. awamori enzymes, under corresponding conditions (10FPU/g bagasse, 20g bagasse/L and 50°C). Hydrolysis experiments, presenting either 20 or 200g/L bagasse, resulted in 3.9 or 40g glucose/L, respectively. These values corresponded to 41% cellulose hydrolysis within 6 or 24h, respectively. A. awamori enzymes hydrolyzed 91% (1.7g/L xylose) of the residual xylan in the bagasse within 6h in experiments presenting 20g/L bagasse.
Keywords: Trichoderma reesei; Aspergillus awamori; Enzyme blends and synergy; Sugarcane bagasse hydrolysis; Cellulases; Xylanases; Ferulic acid esterase
Study of mass transfer and biocatalyst stability for the enzymatic degradation of anthracene in a two-phase partitioning bioreactor by Gemma Eibes; Clare McCann; Alejandro Pedezert; Maria Teresa Moreira; Gumersindo Feijoo; Juan Manuel Lema (pp. 79-85).
In this study the optimal experimental conditions for the degradation of a polycyclic aromatic hydrocarbon in an enzymatic two-phase partitioning bioreactor (TPPB) were investigated. The immiscible organic phase was comprised of silicone oil, acting as a pollutant reservoir for anthracene. This compound underwent degradation by the enzyme versatile peroxidase (VP) produced by the white-rot fungus Bjerkandera adusta. Mass transfer coefficients ( kL a) and enzymatic deactivation constants ( kD) were determined in the TPPB system. The effects of operational parameters such as solvent viscosity (10, 20 and 50cSt), agitation rate (200, 250 and 300rpm) and addition of the non-ionic surfactant Triton X-100 (below its critical micelle concentration, CMC) on the mass transfer and enzymatic decay were investigated. It was ascertained that there was superior enzymatic stability at high values of viscosity. The addition of surfactant below CMC displayed the dual benefit of increasing mass transfer of the substrate fivefold from the organic to aqueous phase whilst also creating a protecting effect upon VP. Optimized conditions led to an 88% oxidation of anthracene after 38h.
Keywords: Two-phase partitioning bioreactor (TPPB); Anthracene; Versatile peroxidase (VP); Mass transfer; Viscosity; Surfactant
Enhanced removal of NH3 during composting by a biotrickling filter inoculated with nitrifying bacteria by Niantao Xue; Qunhui Wang; Chuanfu Wu; Lanhe Zhang; Weimin Xie (pp. 86-93).
A biotrickling filter (BTF) was used to treat NH3 emitted from the exhaust gases of cattle manure compost. Results of the non-biofilm experiment suggested that NH3 could not be removed effectively only through biofilm adsorption. The absence of NH4+ bio-oxidation resulted in an increase in free ammonia, which had a negative effect on NH3 removal. After biofilm culture, NH3 removal efficiency fluctuated between 67.2% and 94.3% because the presence of a biofilm extended the liquid residence time in the packing. When the biofilm was inoculated with nitrifying bacteria comprised of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), which were screened from a cattle manure solution, the average removal efficiencies became 59.9% and 15.0% higher than those of the non-biofilm and biofilm culture experiments, respectively. AOB and NOB could still oxidize ammonia and nitrite, respectively, even when the free nitrous acid concentration was as high as 37.6mg/L. With an empty bed retention time of 96.0s and a removal efficiency of 99%, NH3 elimination capacities were attained at 57.1, 28.6, and 23.7g-N/(m3h) for the first segment, the first and second segment, and the whole BTF, respectively. These results demonstrate that the BTF under study is a viable alternative for the treatment of NH3 during composting.
Keywords: Ammonia; Biotrickling filter; Composting; Inoculation; Nitrifying bacteria; Odor
Erratum to “Modelling of fixed-bed adsorption of mono-, di-, and fructooligosaccharides on a cation-exchange resin” [Biochem. Eng. J. 49 (2010) 84–88]
by Katarína Vaňková; Pavel Ačai; Milan Polakovič (pp. 94-94).