ISSN:0264-3421    

DOI:10.1002/jctb.280340102

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractRedox mediators promote electron transfer in microbial fuel cells. The reduction of a range of redox mediators by bacteria was studied in some detail in order to identify effective mediator—organism combinations. Rates of reduction of mediator dyes by bacteria were measured spectrophotometrically at 30°C under anaerobic conditions for standardised concentrations of organism, substrate and dye. The kinetics of dye reduction showed two general patterns: a simple, exponential curve or a complex curve with an initial linear rate followed by a faster exponential rate of reduction. Dye‐reduction rates were greater than rates of oxygen consumption (QO2) for several combinations of organism and redox dye. Thionine, brilliant cresyl blue, methylene blue and benzyl viologen were tested in combination withAlcaligenes eutrophus, Azotobacter chroococcum, Bacillus subtilis, Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosaandPseudomonas putida, using glucose and succinate as substrates. Rates of reduction of alizarin brilliant blue, 2,6‐dichlorophenolindophenol, gallocyanine, new methylene blue,N,N‐dimethyl‐disulphonated thionine, phenazine ethosulphate, resorufin, safranine‐O, phenothiazinone and toluidine blue‐O were also measured withPr. vulgarisonly. ForE. coli, both QO2and the rate of thionine reduction increased with increasing temperature in the range 25 to 37°C, but forPr. vulgaristhionine reduction rates did not correlate with temperature in this way. Dye‐reduction rates and QO2forAz. chroococcumwere dependent on the components of the washing solution and/or the temperature at which cell suspensions were prepared. The results are discussed in relation to the use of these dyes as electron‐transfer mediators in m

ISSN:0264-3421    

DOI:10.1002/jctb.280340103

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractVarious phenoxazine, phenothiazine, phenazine, indophenol and bipyridilium derivatives were tested for their effectiveness as redox mediators in microbial fuel cells containingAlcaligenes eutrophus, Bacillus subtilis, Escherichia coli, orProteus vulgarisas the active biological agent, and glucose or succinate as the oxidisable substrate. A ferricyanide‐Pt cathode was used. The open‐circuit cell e.m.f.′s increased in the order of increasing negative formal redox potentials at pH 7(E7m) of the redox compounds. Several of the redox agents worked well as mediators, maintaining steady currents over several hours, and thionine was found to be particularly effective in maintaining relatively high cell voltages when current was drawn from the cell. A number of the compounds tested did not function well, either because they were incompletely or slowly reduced by the microorganisms or because of their instability.P. vulgaris, with thionine as mediator and glucose as substrate, showed the best performance in a fuel cell. This system was examined in some detail under various conditions of external load to establish the effects of organism concentration, mediator concentration, and substrate addition. Coulombic outputs from these cells were calculated by integration of the current‐time plots. Coulombic yields of 30–60% were obtained, on the basis of (theoretical) complete oxidation of added substrate to CO2

ISSN:0264-3421    

DOI:10.1002/jctb.280340104

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractIn a CO2‐limited algal culture, grown in a tubular loop photobioreactor, the maximum rate of CO2absorption increased about 1.5‐fold when the culture pH value was increased from 6.5 to 7.5 with a fixed initial PCO2. The mean volumetric CO2transfer coefficient (KLa) increased about 1.8‐fold. The bicarbonate ion concentration would be increased 10‐fold by the pH increase. The effect of pH on the absorption rate is attributed to changes in either the CO2diffusivity, the gas bubble size, or the CO2reaction kinetics at the gas/liquid b

ISSN:0264-3421    

DOI:10.1002/jctb.280340105

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractThis paper develops the kinetics of a substrate‐limited batch culture of bacteria subject to non‐competitive product inhibition. The equation of growth is solved exactly. The expression which represents, growth is shown to consist of the sum of three terms. These correspond to three successive phases: exponential in near‐optimal conditions, linear growth which reflects product inhibition and finally decelerating growth arising from substrate depletion. The extent and distinguishability of the three phases is dependent on the relative values of the growth param

ISSN:0264-3421    

DOI:10.1002/jctb.280340106

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractStreptomyces phaeochromogenescells were immobilised by radiation polymerisation of hydrophilic monomers; highest levels of glucose isomerase activity were found in immobilised cell composites with highly hydrophilic polymer matrices. The enzyme activity in the composites from the copolymerisation of hydroxyethyl acrylate (or methacrylate) andN‐vinyl‐2‐pyrrolidone monomer increased markedly with increase in the content of theN‐vinyl‐2‐pyrrolidone monomer, owing to the higher water absorption by the polymer matrix, and was close to that of the non‐immobilised cells. The enzyme activity was affected by monomer concentration, the hydrophilicity, and chemical structure of the polymer matrix. The Michaelis constant of the composites from hydrophilic monomers was close to that of the

ISSN:0264-3421    

DOI:10.1002/jctb.280340107

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractAn inulinase producingAspergillus nigerstrain was isolated from Compositae rhizosphere soil samples. High inulinase levels were produced on a corn steep liquor (CSL)‐maltose medium in the absence of inulin at 28°C within 110 h of fermentation. Media based on CSL‐sucrose yielded high cell‐bound inulinase activity; on inulin‐based media the enzyme was mainly extracellularly produced. Both crude extra‐and intracellular inulinase preparations displayed identical pH and temperature optima with maximal activity at pH 4.3–4.4 and at 55–56°C. These properties are favourable in view of large scale inulinase application for pure fructose production. High operation temperatures would avoid microbial contamination of reactors and would allow the use of high inulin‐substrate concentrations, a limiting factor in obtaining high conversion ratios. The remarkably low pH optimum prevents colour formation and undesirable chemical side reactions. An advantageous low ratio of invertase to inulinase activity (S/I value) of 0.85 was found for the crude extracellular enzyme preparation. Crude inulin (chicory) extracts are hydrolysed faster than pure inulin. Apart from inulin (100% hydrolysis), sucrose (45%) and raffinose (20%) are also hydrolysed, and no liberation of oligomers or of sucrose from inulin was observed. These facts indicate that theA. nigerenzyme is an exo‐acting inulinase. The above characteristics make thisA. nigerinulinase an industrially attractive enzyme for the preparation of pure fructose from inulin‐containi

ISSN:0264-3421    

DOI:10.1002/jctb.280340108

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe disposal of whey and whey permeate derived from the cheese industry is a serious economic and environmental problem. Lactose in whey permeate was used to synthesise polyether polyols from which rigid, low‐density polyurethane foams were prepared. Resultant foams were comparable to those made from commercially available sucrose‐based polyether polyols. Brown‐coloured lactose polyether polyols are characterised by low viscosity and high carbonyl content. Urea incorporated into these polyether polyols yields flame retardant (self‐extinguishing) foams. Urea also reduced the amount of phosphorus and/or halogen based fire retardants needed to make the foams non‐burning. A preliminary economic analysis indicates that whey‐based polyether polyols can be prepared at a cost savings of up to 36% compared to the sucrose c

ISSN:0264-3421    

DOI:10.1002/jctb.280340109

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractA mathematical model was developed to describe the effect of external mass transfer for a packed‐bed enzyme reactor in which a reversible, one‐substrate, two‐intermediate enzyme reaction took place. The model equation was applied to the analysis of an immobilized glucose isomerase reactor system. A Colburn‐type mass transfer correlation was obtained from the Colburnj‐factor versus Reynolds number plot: i.e.,jD= 0.045NRe−0.48. The values of mass transfer coefficient for the system under study ranged from 0.01 to 0.1 cm h−1depending on the substrate flow rate. Very good agreements were observed between the computer simulation using a plug flow reactor model with the derived mass transfer correlation and the experimental results obtained from the packed‐bed re

ISSN:0264-3421    

DOI:10.1002/jctb.280340110

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY

摘要:

AbstractPeat and its derived products such as peat extracts or hydrolysates offer a variety of possibilities as raw materials for the development of chemical and biochemical processes. Acid hydrolysis of peat yields soluble carbohydrates which can be utilised as fermentation media. In this work,Sphagnumpeat moss was hydrolysed under various conditions of H2SO4concentration, retention time, temperature, peat concentration, peat particle size distribution and original moisture content in the peat. The results suggest that mild conditions of hydrolysis, which will minimise possible negative effects on other nutrients available in peat, are adequate for the release of the carbohydrates present in peat. It was found that peat particle size distribution and original moisture content as well as peat concentration will also affect the yield of carbohydrates obtained.

ISSN:0264-3421    

DOI:10.1002/jctb.280340111

出版商:John Wiley&Sons, Ltd.    

年代:1984

数据来源: WILEY