摘要:

AbstractBiodehalogenation of 10−5Mconcentrations of bromotrichloromethane (BTM) and 1,2‐dibromo‐3‐chloropropane (DBCP) was studied in static cultures ofPseudomonas putidaPpG‐786. The experimental cultures were prepared by growingP. putidaon camphor, which is known to induce the synthesis of high concentrations of cytochrome P‐450 in this bacterium. Measurements of bromide ion release were found to be approximately consistent with the amounts of halocarbon degraded. Gas chromatography/elctron capture detection (GC/ECD) measurements of hydrocarbon degradation products as a function of incubation time showed the transitory appearance of chloroform and bromodichloromethane from BTM and the transitory appearance of lower boiling but unidentified products from DBCP. The degradation of BTM to trihalomethanes and the halide ion is consistent with the enzymatic reductive dehalogenation by cytochrome P‐450 reported by others. The dependence of initial conversion rates on halocarbon concentration (0.1–2 ppm) and cell mass concentration (1–28 g cell/L) was determined by measuring the decline of parent halocarbon in stirred batch cell suspensions. The rate of DBCP conversion was up to 10‐fold higher than the rate of BTM conversion. When the intracellular, enzyme‐catalyzed conversion BTM is analyzed by the effectiveness factor of heterogeneous catalysis, the initial conversion rates measured suggest that intrinsic enzyme kinetics, rather than halocarbon permeation of the cell membrane or other diffusive proces

ISSN:0006-3592    

DOI:10.1002/bit.260290202

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

年代:1987

数据来源: WILEY

摘要:

AbstractCellulase (Cellulosin AC‐8) was immobilized on poly‐L‐glutamic acid. This immobilized cellulase (IC) is water soluble in the neutral and alkaline solutions, where IC has the activity, while IC can be made insoluble by lowering the pH so that it can be recovered from the reaction mixture with its activity. The optimum pH and temperature were determined to be 5.5 and 55°C, respectively. The stability of IC against change in the pH and temperature was improved by the immobilization. Solvolysis of 3N‐NaOH‐treated cellulose, with IC under the optimum conditions found here, led to the production of low‐molecular‐we

ISSN:0006-3592    

DOI:10.1002/bit.260290203

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

年代:1987

数据来源: WILEY

摘要:

AbstractPretreatment of lignocellulosic materials such as newspaper, rice straw, pulp waste, and municipal solid waste with hydrogen peroxide in the presence of manganese compounds greatly enhances their susceptibility to enzymatic saccharification. This pretreatment can be achieved using rather mild conditions with only a minimal decrease in the recovery and little change in composition. Manganese salts in this hydrogen peroxide pretreatment works effectively in particular when the concentration of hydrogen peroxide is relatively low. The susceptibility of hydrogen‐peroxide‐pretreated substrate to enzymatic saccharification increases with increasing the molar ratio of manganes to hydrogen peroxide up to 1 :

ISSN:0006-3592    

DOI:10.1002/bit.260290204

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

年代:1987

数据来源: WILEY

摘要:

AbstractHigher activity of ethanol production due to higher density of yeast cells was observed in yeast cells immobilized with artificial polymer carriers of higher water content based on methoxypolyethyleneglycol methacrylate and 2‐hydroxyethylacrylate. These polymer carriers were prepared by radiation‐induced polymerization below 0°C. Yeast cells were immobilized with these carriers by adsorption method during multiplication. Two possible reasons for higher activity were discu

ISSN:0006-3592    

DOI:10.1002/bit.260290205

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

年代:1987

数据来源: WILEY

摘要:

AbstractEight chemically modified cellulose supports were tested for their ability to absorb components of theAspergillus nigercellulase system. At least two of the most effective adsorbents, aminoethyl cellulose and carboxymethyl cellulose, were shown to be useful for the fractionation of cellulases. These supports apparently owe their resolving capacity to both ion exchange and biospecific binding effects; however, the relative importance of each effect is unknown. These observations form the basis for a new cellulase fractionation technique, combined ion exchange–affinity chromatograph

ISSN:0006-3592    

DOI:10.1002/bit.260290206

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

年代:1987

数据来源: WILEY

摘要:

AbstractThere are many scaling formulas that predict the oxygen mass transfer coefficient askL·a= constant·(Hp/V)αVsβExponents α and β frequently are scale dependent themselves. A general formula has been derived from the work of Calderbank,1Miller,2and Tilton,3resulting inkL·a=C1ϕ +C2log (Pm/V) ϕ where ϕ equals the gas‐holdup fraction andPm/Vequals the effective mechanical power input per unit of volume. This formula is consistent with the formula of Westerterp4modified by Miller.2Gas holdup can be predicted in several ways. Gas‐sparged isothermal expansion power input, used for predicting ϕ, demonstrates that scaling can be done by using either superficial air velocity or volume per volume per minute for aeration.The importance of mixing in replenishing oxygen at the boundary layers of microorganisms will be assessed and compared with thekL·aas the oxygen transfer ra

ISSN:0006-3592    

DOI:10.1002/bit.260290207

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

年代:1987

数据来源: WILEY

摘要:

AbstractLet us consider the modeling of a cascade reactor for the production of ethanol. The rates of reaction in alcoholic fermentation are modeled so that it can assume both ethanol and substrate inhibition, in relation to the observed results.A nonstructured model, based on biomass, substrate, and ethanol concentrations, is developed and identified. It is a complex model, this being due to the nonlinearity between the specific rate of ethanol production and the growth rate and, on the other hand, the study of the static optimization of ethanol fermentation is performed.

ISSN:0006-3592    

DOI:10.1002/bit.260290208

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn Part I1of this research a complex model was obtained for describing the ethanol fermentation in a cascade reactor. This complexity is due to both the nonlinearity and the large scale representation. Based on techniques of partitioning and relaxation, a decentralized successive approximation method is developed for static optimization. The influence of the way of fermentation during continuous culture in multistage fermentors is studied in the case of a double inhibition of cell growth and product formation by both substrate and final product. The optimal number of reactors is discussed with respect to the strength of the ethanol inhibition, while the interest of head feeding or distributed feeding is evaluated in relation to the strength of substrate inhibition.

ISSN:0006-3592    

DOI:10.1002/bit.260290209

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe electrochemical transient of a two‐substrate enzyme electrode was studied theoretically and experimentally. Operation of such electrodes in the chronocoulometric mode leads to increased electrode sensitivity and makes possible the retrieval of useful information on transport and kinetics parameters. Digital simulation was used to solve the kinetics and transport equations and to produce the theoretical chronocoulometric response. A glucose electrode based on glucose oxidase crosslinked to different matrices was tested with air oxygen andp‐benzoquinone as the cosubstrate. A computerized electrochemical system was employed for electrode potential control and data acquistion and analy

ISSN:0006-3592    

DOI:10.1002/bit.260290210

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

年代:1987

数据来源: WILEY

摘要:

AbstractAn auxotrophic mutant ofSaccharomyces cerevisiae, containing a recombinant 2‐μ‐based plasmid, was grown in selective media in continuous culture. The plasmid retained the ability to synthesize acid phosphatase as product, which was deleted from the host. Plasmid loss was followed at various dilution rates, and the level of plasmid expression was controlled by changing the β‐glycero/inorganic phosphate ratio.Some interesting trends were observed. As the level of plasmid expression was raised, the stability dropped markedly. Since acid phosphatase expression is regulated at the level of transcription, it is possible that increased transcription interfered with plasmid replication, hindered segregation, or overburdened the cell's DNA repair capability. It was also observed that plasmid stability was substantially increased at high growth rates. At dilution rates of 0.3 and 0.37 h−1, feeding only inorganic phosphate, the plasmid was complete

ISSN:0006-3592    

DOI:10.1002/bit.260290211

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

年代:1987

数据来源: WILEY