摘要:

AbstractEnvironmental concern about sulphur dioxide emissions has led to the examination of the possibility of removing pyritic sulphur from coal prior to combustion during froth flotation, a routine method for coal cleaning at the pit‐head. The bacteriumThiobacillus ferrooxidanswas effective in leaching 80% and 63% −53 μm pyrite at 2% and 6% pulp density in shake flasks in 240 and 340 h, respectively.The natural floatability of pyrite was significantly reduced in the Hallimond tube following 2.5 min of conditioning in membrane‐filtered bacterial liquor prior to flotation. The suppression effect was greatly enhanced in the presence of Thiobacillus ferrooxidans. A bacterial suspension in pH 2.0 distilled water showed 85% suppression, whereas in spent growth liquor this value was 95%. The optimum bacterial density was 3.25 × 1010cells/g pyrite in 230‐ml distilled water (2% pulp density) in the Hallimond tube. The degree of suppression by the cells was related to particle size but not to pH or temperature. The sulphur content of a synthetic coal/pyrite mixture was reduced from 10.9 to 2.1% by flotation after bacterial preconditioning. It is postulated that pyrite removal in coals which are cleaned by froth flotation could be significantly reduced using a bacterial preconditioning stage with a short residence time o

ISSN:0006-3592    

DOI:10.1002/bit.260300102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractDuring unsteady‐state continuous culture ofSaccharomyces cerevisiaeon sugarcane blackstrap molasses, the invertase activity of the intact yeast cells oscillated. Disturbances were produced by changing medium composition, air rate, impeller speed, and dilution rate. The influence of the oxygen supply rate and of the dilution rate on the invertase activity depend on the medium composition. The highest invertase activity was obtained when, after a steady‐state attained using unsupplemented culture medium, nutrients were added to the feeding mash. A Monod‐like equation seems to be the best representation of the correlation between the specific rate of reducing sugars consumption and the specific rate of nonreducing sugar hydrolysis by the yeast

ISSN:0006-3592    

DOI:10.1002/bit.260300103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractThe effect of surface coverage of biomass on biofilm kinetics in an expanded‐bed, granular activated carbon an aerobic reactor was evaluated. Acetate was used as the sole organic carbon source. An assumption of 10% surface coverage of biofilm was examined and compared to 100% coverage. Best estimated values ofkaandKsadid not differ significantly from one case to the other. The confidence region analysis also showed that the biofilm was fully penetrated in the expanded‐bed reactor for the case of 10% coverage, as well as when 100% coverage was assumed. Because the biofilm was fully penetrated, a model having no internal diffusion resistance and using the best estimates ofkaandKsaobtained from the 10 and 100% coverage assumptions was capable of giving good predictions of effluent acetate concentrations for an in dependent experiment having a reduced liquid detention time. Consideration of biofilm surface‐loading criteria demonstrated how the results can be applied to other reactors for the purpose of predicting when the extent of surface coverage and internal diffusion resistance are not significant factors in biofilm mod

ISSN:0006-3592    

DOI:10.1002/bit.260300104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractA new immobilized cell system providing protection against toxic solvents was investigated so that normal fermentations could be carried out in a medium containing toxic solvents. The system consists of immobilized growing cells in Ca‐alginate gel beads to which vegetable oils, which are inexpensive absorbents of solvents, had been added. The ethanol fermentation ofSaccharomyces cerevisiaeATCC 26603 was used as a model fermentation to study the protection afforded by the system against solvent toxicities. The fermentation was inhibited by solvents such as 2‐octanol, benzene, toluene, and phenol. Ethanol production of one batch was not finished even after 35 h using immobilized growing yeast cells in conventional Ca‐alginate gel beads in an ethanol production medium (5% glucose) containing 0.1% 2‐octanol, which is used as a solvent for liquid‐liquid extraction and is one of the most toxic solvents in our experiments. With the new immobilized growing cell system using vegetable oils, however, four repeated batch fermentations were completed in 35 h. Castor oil provided even more protection than soy bean, olive, and tung oils, and it was possible to complete six repeated batches in 35 h. The immobilized cell system with vegetable oils also provided protection against other toxic solvents such as benzene and toluene. A possible mechanism for the protective function of the new immobilized cell system is

ISSN:0006-3592    

DOI:10.1002/bit.260300105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractPolymers produced by horseradish‐peroxidase‐catalyzed coupling of phenols have been explored as potential substitutes for phenol‐formaldehyde resins. To overcome low substrate solubilities and product molecular weights in water, enzymatic polymerizations in aqueous‐organic mixtures have been examined. Peroxidase vigorously polymerizes a number of phenols in mixtures of water with water‐miscible solvents such as dioxane, acetone, di‐methylformamide, and methyl formate with the solvent content up to 95%. As a result, various phenolic polymers with average molecular weights from 400 to 2.6 × 104D were obtained depending on the reaction medium composition and the nature of the phenol. Peroxidase‐catalyzed copolymerization of different phenols in 85% dioxane was demonstrated. Poly(p‐phenylphenol) and poly(p‐cresol) were enzymatically prepared on a gram scale. They had much higher melting points, and in addition, poly(p‐phenylphenol) was found to have a much higher electrical conductivity than phenol

ISSN:0006-3592    

DOI:10.1002/bit.260300106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractA methodology for mathematically analyzing agitator performance and mass transfer in large multiturbine production fermentors is presented. The application of this approach provides a method for determining axial dissolved oxygen profiles under conditions of known mass transfer rates as a function of agitation–aeration characteristics. A stagewise approach is used which divides the fermentor into a series of mixing cells. This allows for each turbine and mixing cell to be individually optimized. The model also permits the determination of the mass transfer coefficient for each turbine based upon limited dissolved oxygen data. The primary limitation of this approach rests in the limited data and correlations available for multiturbine systems. The structure of the modelling approach can serve as a basis for testing single turbine correlations and adapting them to multiturbine systems. The step‐by‐step details of the mathematical analysis are presented and interpreted. A series of computer simulations demonstrate the effect of typical fermentor operating variables on the axial dissolved oxygen profile. Further simulations demonstrate the effect of modifying agitator blade numbers on the dissolved oxygen profile and agitator power requir

ISSN:0006-3592    

DOI:10.1002/bit.260300107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractA new method (polyvinyl alcohol–boric acid method) for an inexpensive and effective immobilization of activated sludge was developed. Using activated sludge immobilized by this PVA–boric acid method, synthetic waste‐water was treated at a high loading rate of 0.5–2.35 kg TOC/m3day. Total organic carbon and total nitrogen were removed at efficiencies of 93 and 30–40%, respectively. The kinetic constantsYandbfor this immobilized activated‐sludge process were determined to be 0.594g mixed liquor suspended solids (MLSS)/g TOC and 0.0219 day−1, respectively. The cost calculation of chemicals required for the immobilization of activated sludge by this PVA–boric acid method was proved to be extremely inexpensive for the immobilization of a

ISSN:0006-3592    

DOI:10.1002/bit.260300108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractMixing and stirring of a 20‐m2shallow pool by means of a drag board device has been investigated. The board closes the pool cross section except for a slit of a few centimeters above the bottom, and it is slowly moved back and forth, forcing the water to run through the slit and thereby creating a turbulent backwhirl. Power drawn and the drag on the board has been measured together with the velocities of the water at different locations in the wake of the board. Power numberNphas been correlated with the ReynoldsNReand the bottom clearance numbersNcby the expressions\documentclass{article}\pagestyle{empty}\begin{document}$$ N_p = 13,465N_{\rm Re}^{-0.774} N_c^{0.1016} N_{\rm Re} 80.000 $$\end{document}Power and Reynolds numbers are defined as usual with the square root of the board‐immersed‐area as the characteristic length. The bottom clearance number is defined as the ratio of the water depth in the pool to the difference between water depth and the board width immersed in water. Flow pattern behind the board consists of large vortex loops causing the fluid to circulate from bottom to top and producing a thorough mixing effect. The drag board seems to have several advantages over conventional paddle wheels for the mixing and stirring of algal cultures in shallow

ISSN:0006-3592    

DOI:10.1002/bit.260300109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractPolyacrylamide gel‐immobilized cells of aCitrobactersp. removed cadmium from flows supplemented with glycerol 2‐phosphate, the metal uptake mechanism being mediated by the activity of a cell‐bound phosphatase that precipitates liberated inorganic phosphate with heavy metals at the cell surface. The constraints of elevated flow rate and temperature were investigated and the results discussed in terms of the kinetics of immobilized enzymes. Loss in activity with respect to cadmium accumulation but not inorganic phosphate liberation was observed at acid pH and was attributed to the pH‐dependent solubility of cadmium photsphate. Similarly high concentrations of chloride ions, and traces of cyanide inhibited cadmium uptake and this was attributed to the ability of these anions to complex heavy metals, especially the ability of CN−to form complex anions with Cd2+. The data are discussed in terms of the known chemistry of chloride and cyanide‐cadmium complexes and the relevance of these factors in the treatment of metal‐containing liquid wastes is discussed. The cells immobilized in polyacrylamide provided a convenient small‐scale laboratory model system. It was found that theCitrobactersp. could be immobilized on glass supports with no chemical treatment or modification necessary. Such cells were also effective in metal accumulation and a prototype system more applicable to the treatment of metal‐containing streams on a larger s

ISSN:0006-3592    

DOI:10.1002/bit.260300110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY

摘要:

AbstractA research project was initiated to examine the possibility of using supercritical carbon dioxide forin siturecovery of ethanol during its production by yeastSaccharomyces cerevisiae. As a preliminary step, it was necessary to study the behavior of ethanol production under high‐pressure conditions, up to 7 MPa (1000 psi). The results show that pressure has a significant inhibiting effect on the production of ethanol. There is a significant decrease in the initial rate of production as well as in the final ethanol concentration as pressure is increased. This decrease is more significant when carbon dioxide is used to pressurize the fermentor. The pressure affects the ability of the cells to produce ethanol in a reversible way. When the fermentor is returned to atmospheric conditions, the reaction resumes its normal fermentation rat

ISSN:0006-3592    

DOI:10.1002/bit.260300111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1987

数据来源: WILEY