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Applied Biochemistry and Biotechnology: Part A: Enzyme Engineering and Biotechnology (v.110, #3)
Biofiltration of 1,1,1-trichloroethane by a trickle-bed air biofilter by Chungsying Lu; Kwotsair Chang (pp. 125-136).
The performance of a trickle-bed air biofilter (TBAB) in the removal of 1,1,1-trichloroethane (TCLE) was evaluated in concentrations varying from 0.025 to 0.049 g/m3 and at empty-bed residence time (EBRT) varying from 20 to 90 s. Nearly complete TCLE removal could be achieved for influent carbon loading between 0.98 and 5.88 g/m3 h. The TBAB appeared efficient for controlling TCLE emission under low-carbon-loading conditions. Carbon recoveries higher than 95% were achieved, demonstrating the accuracy of results. The carbon mass rate of the liquid effluent was approximately two orders of magnitude less than that of the effluent CO2, indicating that dissolved TCLE and its derivatives in leachate were present in negligible amounts in the TBAB.
Keywords: Biofiltration; trickle-bedair biofilter; 1,1,1-trichloroethane; empty-bed residence time; influent concentration
Olive husk by Angela Volpe; Antonio Lopez; Michele Pagano (pp. 137-149).
Sorption properties of olive husk were investigated under equilibrium (batch tests) and dynamic (column tests) conditions in order to assess the possibility of using such a waste material for removing heavy metals from aqueous streams. Husk samples were contacted, at 25°C, with aqueous solutions of nitric salts of Pb, Cd, Cu, and Zn. Sorption isotherms obtained from equilibrium data were fitted and interpreted by the Freundlich model. Metals-saturated husk samples resulting from column tests were air-dried and incinerated to simulate combustion in order to assess the fate of sorbed metals. The results demonstrated that, under both equilibrium and dynamic conditions, metal sorption capacity of the husk was in the sequence Pb>Cd>Cu>Zn. For all the metals, calculated Freundlich constants decreased by increasing initial metal concentration or decreasing solution pH. In dynamic tests, a significant reduction of sorption capacity was recorded (except for copper) when a metal was fed simultaneously to the others: Pb (77%); Cd (93%); Zn (68%). Combustion tests carried out on metals-saturated husk samples showed that the average losses of lead and cadmium, as volatile species, were always three to four times greater than the losses of copper and zinc, in both single-metal- and multimetal-saturated samples.
Keywords: Heavy metals; sorption; olive husk; wastewater
Ethanol production by Saccharomyces cerevisiae grown in sugarcane blackstrap molasses through a fed-batch process by João C. M. Carvalho; Michele Vitolo; Sunao Sato; Eugênio Aquarone (pp. 151-164).
We studied the effect of reactor filling time (T) (3–5 h), initial mass of inoculum (M) (1000–2100 g), and exponential time decay constant for the substrate feed rate (K) (0.6–1.6 h−1) on ethanol production by Saccharomyces cerevisiae grown in sugarcane blackstrap molasses through a fed-batch culture. The highest ethanol productivity (16.9 g/[L·h]) occurred at T=3h, K=1.6 h−1, and M=1300 g. In addition, productivity was affected by both M (for T=3 and 4 h) and K (for T=3 h) and varied inversely with T under any value fixed for M and K. By the quadratic regression multivariable analysis method, equations were determined to estimate ethanol yield and productivity as function of the variables studied (T, K, and M).
Keywords: Ethanol; Saccharomyces cerevisiae ; fed-batch fermentation; response surface methodology
Interaction of glucose oxidase with alkyl-substituted sepharose 4B by Saman Hosseinkhani; Ali Akbar Moosavi-Movahedi; Mohsen Nemat-Gorgani (pp. 165-174).
Glucose oxidase (GOD) is often used in immobilized forms for determination of glucose. To examine the possibility of its adsorption by hydrophobic interactions, palmityl-substituted Sepharose 4B (Sepharose-lipi) was employed as an adsorptive matrix. Various conditions were used in tests to improve the limited immobilization of the enzyme observed undernormal (native) conditions, including use of high concentrations of denaturing agents. Of the denaturants used, only the cationic detergent dodecyl trimethyl ammonium bromide was effective in denaturing the protein and exposing its hydrophobic sites for interaction with alkyl residues on the support. This, followed by the process of renaturation, provided catalytically active immobilized preparations. The apoenzyme, prepared by treatment of the holoenzyme with acidified (NH4)2SO4 or thermal denaturation, was totally immobilized on the support. Furthermore, it was shown that either flavin adenine dinucleotide (FAD) or the alkyl residues, not both, may interact with the nucleotide site at any given time. Results are discussed in terms of high rigidity of GOD molecule and limited exposure of hydrophobic sites in its native structure. The observations are in accord with suggestions in the literature that the FAD pocket is a very narrow channel of hydrophobic properties, adapted to accept its natural coenzyme.
Keywords: Glucose oxidase; adsorptive immobilization; hydrophobic matrices; molten globule; 8-anilinonaphtalene-I-sulfonate
Effect of chitosan on peroxidase activity and isoenzyme profile in hairy root cultures of Armoracia lapathifolia by Cecilia G. Flocco; Ana María Giulietti (pp. 175-183).
Hairy root cultures of Armoracia lapathifolia established by infection with Agrobacterium rhizogenes LBA 9402 present a level and isoenzyme pattern of peroxidases (POD) comparable to nontransformed roots. Elicitation with chitosan (10, 50, and 100 mg/L) was used in order to improve POD production. Total POD activity increased about 170% after 48h of treatment with chitosan 100 mg/L. Elicitation effect on soluble and ionically cell-wall-bound POD fractions of A. lapathifolia hairy roots was analyzed. POD activity of the ionically cell-wall-bound protein fraction increased in the presence of chitosan in a dose-response manner. No effect on soluble POD fractions was observed, but the isoenzyme pattern analyzed by isoelectrofocusing showed an increase of an acidic isoenzyme (pI=3.4) after the elicitation treatment. The ionically cell-wall-bound protein fraction showed only basic isoenzymes, with an increase of an isoenzyme of pI=8.7, after the elicitation treatment.
Keywords: Armoracia lapathifolia ; transformed root culture; peroxidase production; chitosan; elicitation