摘要:

AbstractConidia ofAspergillus nigerTMB 2022 were immobilized in calcium alginate for the production of citric acid. A 1‐mL conidia suspension containing ca. 2.32 × 108conidia were entrapped into sodium alginate solution in order to prepare 3% Ca–alginate (w/v) gel bead. Immobilized conidia were inoculated into productive medium containing 14% sucrose, 0.25% (NH4)2CO3, 0.25% KH2PO4, and 0.025% MgSO4·7H2O with addition of 0.06 mg/L CuSO4·5H2O, 0.25 mg/L ZnCl2, 1.3 mg/L FeCl3·6H2O, pH 3.8, and incubated at 35°C for 13 days by surface culture to produce 61.53 g/L anhydrous citric acid. Under the same conditions with a batchwise culture, it was found that immobilized conidia could maintain a longer period for citric acid production (31 days): over 70 g/L anhydrous citric acid from runs No. 2–4, with the maximum yield for anhydrous citric acid reaching 77.02 g/L for run No. 2. In contrast, free conidia maintained a shorter acid‐producing phase, ca. 17 days; the maximum yield for anhydrous citric acid was 71.07 g/L for run No. 2 but dropped quickly as the run numb

ISSN:0006-3592    

DOI:10.1002/bit.260290302

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe production of 4‐androstene‐3, 17‐dione byFlavobacterium dehydrogenansfrom androstenolone–acetate in octane/culture (v/v = 1:1) two‐liquid phase systems was compared with the conversion rate in a Tween‐containing medium commonly used in industry, and in a culture where no organic solvent or detergent was added. Variation of the cell density of the cultures at the moment of steroid, Tween, and/or organic solvent addition showed that the highest conversion rate in the three systems was reached with cells which were in the late exponential growth stage. The rate of 4‐androstene‐3, 17‐dione production at the optimal cell density in the two‐liquid‐phase system and Tween medium were ca. 6 and 1½ times as high, respectively, as in the aqueous medium without addition. The beneficial effect of octane on the rate of steroid conversion during growth could be explained by viability changes as measured by a new method to determine viability. Furthermore, our results show that a very high degree of conversion can be reached in the two‐liquid‐phase system [more than 98% (w/w)] which cannot be obtained in an aqueous medium. An easy way to recover the product

ISSN:0006-3592    

DOI:10.1002/bit.260290303

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

年代:1987

数据来源: WILEY

摘要:

AbstractHydrogen‐limited chemostat cultures ofMethanobrevibacter arboriphilusA2 were carried out. The available electron balance and carbon balance inM. arboriphilusA2 and other methanogenic strains grown on various substrates were well satisfied. This indicates that no extracellular organic products were formed during methanogenic growth. The molar growth yields for methane (Y X/CH 4) were calculated as 1.06–1.42 g cell/mol CH4at dilution rate (0.21–0.43 day−1). The smallerY X/CH 4ofM. arboriphilusA2 compared with that of the other methanogenic strains was probably owing to the low growth rate ofM. arboriphilusA2. The low value ofY X/CH 4may be favorable for methane fermentation because less sludge accumulation is expected. The efficiency of free energy transduction to ATP during methane formation from H2+ CO2was 12–17% at the dilution rate (0.21–0.43 day−1) assuming thatYATPwas 6.5 g/mol and the free energy change of CO2reduction to methane with H2was −62.8 kJ/mol und

ISSN:0006-3592    

DOI:10.1002/bit.260290304

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

年代:1987

数据来源: WILEY

摘要:

AbstractA mechanistically detailed single‐cell modelE. coliB/r‐A was adapted to simulate the effects of vector presence on cell metabolism. Competition for RNA polymerase between chromosome and plasmid DNA is explicitly included. Distribution of active ribosomes among chromosome‐ and plasmid‐derived messenger RNA, another key facet of host–plasmid interactions, is also treated in detail. Simulations of recombinant cell growth rate and cloned‐gene productivity as a function of relative plasmid number per cell agree closely with experimental results. Model prediction of the variation of cell cycle parametersCandDwith plasmid number are roughly consistent with available data. Models of this class can be used to simulate changes in productivity resulting from specific alterations in the expression vector. The effects of changing cloned‐gene promoter and ribosome binding strengths and of augmenting cell transcription or translation capacity have been studied using the recombinant cell model. Results suggest that cloned‐gene expression is limited by cellular transcription capacity. These and other parametric studies, conveniently implemented using the computer cell, provide important guidance for future experiments directed at better understanding of host–plasmid interactions and at optimizing recombinant sy

ISSN:0006-3592    

DOI:10.1002/bit.260290305

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

年代:1987

数据来源: WILEY

摘要:

AbstractA study was performed to optimize the production of solvents from whey permeate in batch fermentation usingClostridium acetobutylicumP262. Fermentations performed at relatively low pH values resulted in high solvent yields and productivities, but lactose utilization was incomplete. At higher pH values, lactose utilization was improved but acid production dominated over solvent production. When operating at the higher pH values, an increase in the initial lactose concentration of the whey permeate resulted in lower rates of lactose utilization, and this was accompanied by increased solvent production and decreased acid production. Analysis of data from several experiments revealed a strong inverse relationship between solvent yield and lactose utilization rate. Thus, conditions which minimize the lactose utilization rate, such as low culture pH values or high initial lactose concentrations, favor solventogenesis at the expense of acid production.

ISSN:0006-3592    

DOI:10.1002/bit.260290306

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

年代:1987

数据来源: WILEY

摘要:

AbstractA bisubstrate system havingSs1>Smin 1was tested with phenol and acetate as model compounds in completely mixed biofilm reactors. Two series of experiments compared the kinetics of phenol removal as a single substrate and as part of a bisubstrate system having a fixed total feed COD. Experimental results showed that, although the rate of utilization of either substrate was almost the same in a bisubstrate system as in a single substrate system, the utilization rate of either compound always was slightly greater in a bisubstrate system than in a single‐substrate system. This slight enhanced removal of an individual compound in a bisubstrate system was attributed to the extra biomass accumulated from the utilization of the other substrate. As the fraction of the feed COD contributed by an individual compound decreased in a bisubstrate system, the effluent concentration of that compound decreased and its fractional removal efficiency increased. The bisubstrate secondary‐utilization model successfully described the experimental results and explained the differences that occurred as phenol became a smaller fraction of the fixed total feed

ISSN:0006-3592    

DOI:10.1002/bit.260290307

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

年代:1987

数据来源: WILEY

摘要:

AbstractA solid acid catalyst consisted of sulfonic groups covalently bound to an inorganic matrice was developed to dehydrate 2,3‐butanediol into methyl ethyl ketone. Rate constant and apparent activation energy of the dehydration reaction were determined. The decay course of the catalyst was a two‐stage curve. The catalyst was deactivated more rapidly in the first stage than in the second stage. The strategy of maintaining constant degree of dehydration was employed to lengthen the lifetime of catalyst. Treatment of the 2,3‐butanediol containing fermentation broth with activated carbon greatly facilitated the subsequent dehydration rea

ISSN:0006-3592    

DOI:10.1002/bit.260290308

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

年代:1987

数据来源: WILEY

摘要:

AbstractKrill chitin modified with carbon disulfide was used as a support of enzymes. The dithiocarbamino groups created after reaction of CS2with chitinous NH2can participate in binding the enzymes without denaturation and loss in activity. The stability of these bonds depends on pH and decreases gradually at ionic strengths higher than 0.01. Chitin modified with CS2can be used as a support for enzymes having high activity at mild conditions of pH and ionic strength.

ISSN:0006-3592    

DOI:10.1002/bit.260290309

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

年代:1987

数据来源: WILEY

摘要:

AbstractAn identifiedEnterobacter aerogenesutilizing methanol as a sole carbon source was studied for the optimization of biomass production and the reduction of its nucleic acid content. Results indicated that the highest yield and conversion were obtained at 0.5% methanol. The addition of seawater as a source of trace elements has an adverse effect. However, the addition of urea as source of nitrogen enhanced the growth ofE. aerogenes. Heat shock at 60°C for 1 min followed by incubation at 50°C for 2 h caused 72.6% reduction in the nucleic aci

ISSN:0006-3592    

DOI:10.1002/bit.260290310

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe yeastTrichosporon beigeliiproduced the highest amount of biomass when grown in chemical‐defined medium with a ratio of carbon source to nitrogen source of 30:1. On the other hand, carbon‐limited medium (C–N ratio 2:1) enhanced unsaturated fatty acids synthesis. The yeast efficiently converted unsalted whey lactose to biomass, while sodium chloride in whey raised lactose assimilation to single‐cell oi

ISSN:0006-3592    

DOI:10.1002/bit.260290311

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

年代:1987

数据来源: WILEY