摘要:

AbstractA reaction engineering model for the degradation of an inhibitory substrate by a steady‐state biofilm is presented. The model describes both the metabolic rate controlling behavior of this substrate in the biofilm and the effect of diffusion limitation caused by an arbitrary substrate on the active biofilm thickness. An analytical expression for the biocatalyst effectiveness factor is presented on the basis of Pirt kinetics for cell maintenance, first order substrate inhibition kinetics, and zero order substrate consumption kinetics. The proposed expression for the biocatalyst effectiveness factor is much more convenient to incorporate into a macroreactor model than the numerical alternatives. Simple criteria are presented to check the applicability of the model in case of true Monod kinetics. The analytical solution is expected to be particularly applicable to processes where a low soluble organic substrate controls the biomass growth, a situation which is often met in wastewater purification processes of industrial importance. The degradation of phenol byPseudomonassp. is treated as an example. © 1993 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260420302

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

年代:1993

数据来源: WILEY

摘要:

AbstractTwo‐dimensional image analysis was applied to counting, sizing, and density determinations of granules in full‐scale and laboratory‐scale upflow anaerobic sludge blanket (UASB) digesters. An advantage of this technique for monitoring laboratory‐scale digester sludge is the small amount of material required for analysis. Quantification of number of granules using this method correlated well with dry weight determinations (r= 0.989). Distinguished granule size increased with time throughout the digestion process, supported by dry weight determinations which indicated an increase in biomass. The monitoring of granule density may reveal subtleties of the selection pressure placed on granules not noticed previously. © 1993 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260420303

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

年代:1993

数据来源: WILEY

摘要:

AbstractA novel procedure is proposed for determining distributions of rate properties and correlations of rate with state properties of microbial cell populations. The procedure is novel in that it uses transient data, and thus, it does not require that the population be in balanced growth, although it requires that the population structure does not change during the short transient experiment. The procedure is applied to populations of the ciliated protozoanTetrahymenato determine ingestion rate variability. The number of ingested microspheres per cell and the single‐cell protein content—an indicator of cell size—were directly determined with dual‐color flow cytometry. The proposed technique revealed the correlation pattern of the particle ingestion rate with cell size. In particular, ingestion rate was found to be positively correlated with cell size for the smaller feeding cells and to be uncorrelated with size for the larger cells. Using the fact that particle uptake from dilute particle suspensions is a Poisson random process, we determined that the coefficient of variation of the distribution of ingestion rates within the feeding population is about 50%. It was concluded that the dynamics of particle ingestion can be accurately described only if it is realized that particle ingestion rates are distributed. © 1993 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260420304

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

年代:1993

数据来源: WILEY

摘要:

AbstractIntracellular pH (pHi) was measured on‐line in a bioreactor using a fluorescent pHiindicator, 9‐aminoacridine, and controlled fed‐batch cultivations of yeast cells based on pHi(FB‐pHi) were performed. In FB‐pHicultivations, automated glucose additions were made to the culture in response to culture pHi. The average ethanol (an‐aerobic product) yield was significantly lower [0.12 g g−1glucose in fed‐batch pHicultivations with 100 ppm glucose additions (FB‐pHi‐100 cultivation) vs. 0.48 g g−1glucose in batch] and cell yield was higher (0.54 g g−1glucose in FB‐pHi‐100 cultivation vs. 0.3 g g−1glucose in batch) compared to batch cultivation. An expression has been derived to calculate changes in pHifrom measured fluorescence values when the cell concentration increases during growth. Cultivations based on pHi, performed with different magnitudes of glucose addition (100, 50, and 10 ppm additions), showed that lower magnitudes of glucose addition resulted in lower ethanol yields while cell yield remained unaffected. The ratio of specific oxygen uptake rate to specific glucose uptake rate (OUR/GUR) increased with decreased in magnitude of glucose additions in FB‐pHicultivations, suggesting that the culture aerobic state was higher when the magnitude of glucose addition was lower. The average cell productivity in FB‐pHicultivations was 29% higher than in batch cultivation. Cells were also cultivated at high OUR conditions, and the results are compared with other cultivat

ISSN:0006-3592    

DOI:10.1002/bit.260420305

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

年代:1993

数据来源: WILEY

摘要:

AbstractGluco‐oligosaccharides were synthesized through the enzymatic condensation ofD‐glucose at high concentration using a commercial almond β‐glucosidase. The synthesis reactions were carried out with both free and immobilized enzyme, with or without sorbitol, an efficient depressor of water activity (aw) in the presence of different glucose concentrations. The yield and the composition of the gluco‐oligosaccharides produced changed with the reaction mixture and the form of the enzyme used (free or immobilized). The use of 5Mglucose solution permitted only disaccharides to be obtained, whereas with a glucose concentration of 7.5Mglucose, di‐, tri‐, and tetrasaccharides were produced. A 7.5Mglucose solution used with 4.4Msorbitol gave three times more disaccharides than the same solution without sorbitol. Moreover, the immobilized enzyme was much more active in synthesis. The synthesis yield (oligomers mg/mL · mg of enzyme) after immobilization was 573% compared to that of the free enzyme, when a 7.5Mglucose solution was tested. The effects of substrate concentration, sorbitol addition and enzyme immobilization were investigated. © 1993 John W

ISSN:0006-3592    

DOI:10.1002/bit.260420306

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe esterification of someN‐benzyloxycarbonyl (Z)‐dipeptides in ethanol‐containing water was investigated using papain as a catalyst. The esterification took place in ethanol containing a samll amount of water (2% v/v, pH 9) with free papain at room temperature. The yield (after 24 h) of the ethyl ester was in the range of 25% to 50%. Any peptide bond cleavage of the substrates was not observed during esterification, indicating that the unfavorable amidase activity of papain was well depressed under these conditions. However, dipeptides having a D‐amino amino acid (Z‐valyl‐D‐alanine) or a bulky amino acid (Z‐valylvaline) at theC‐terminal position could not be esterified. It was found that the immobilization of papain on Amberlite XAD‐8 increased the yield of the ester significantly as compared with free papain. In the esterification ofZ‐valylalanine using immobilized papain, the optimum water content, pH of an added buffer, and temperature were found to be 2% (v/v), 9, and 40°C, respectively. The water content affected the yield of the product ester significantly.© 19

ISSN:0006-3592    

DOI:10.1002/bit.260420307

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis study's objective was to clarify both experimentally and theoretically whether a vertical multistage tower aeration tank system is advantageous as compared with a completely mixed system, particularly with respect to purification efficiency, sludge settleability, and excess sludge production. In comparing the two systems: (1) purification efficiency in the multistage tower aeration system with partial fluid mixing with a large Peclet number was higher than in a corresponding completely mixed system for all applied organic loadings; (2) the multistage tower aeration system had some definite advantages with respect to sludge settleability and excess sludge production; (3) the activated sludge system's higher performance with partial fluid mixing was shown quantitatively with the axial dispersion model in conjunction with growth kinetics which involved rapid uptake such as biosorption and subsequent oxidative biodegradation processes of organic substances. © 1993 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260420308

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

年代:1993

数据来源: WILEY

摘要:

AbstractFusarium solani pisirecombinant cutinase, solubilized in AOT/isooctane‐reversed micelles, was used to catalyze the esterification of fatty acids with aliphatic alcohols. Some relevant parameters for the enzyme activity such as pH,Wo(water/surfactant molar ratio), temperature, and substrate concentration were optimized. Maximal specific activity was obtained for hexanol. The cutinase showed selectivity for short‐chain fatty acids. The stability of the microencapsulated cutinase was investigated at various concentrations of water and different values of pH. Oleic acid had a negative effect on the cutinase stability, while hexanol proved to be a strong stabilizer increasing the half‐life of the enzyme about 45 times. © 1993 John Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260420309

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe explored the use of charged fusions for selective recovery of β‐galactosidase from cell extract using a low‐cost, easily scaled, fast, charge‐based separation technique—ion exchange on hollow fiber ion‐exchange membranes (HFIEMs). The additional charges carried by a series of anionic fusion tails allowed selective binding and release of β‐galactosidase fromEscherichia colicell extract using the HFIEM cartridge. The purification factors increased with fusion length. The β‐galactosidase was recovered in active form. For the longest fusion studied, more than sixfold enrichment in specific activity was attained. The specific activity of the recovered fraction is comparable with that of commercial wild‐type β‐galactosidase and affinity‐purified fusion protein. © 1

ISSN:0006-3592    

DOI:10.1002/bit.260420310

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

年代:1993

数据来源: WILEY

摘要:

AbstractAnimal cell bioreactors are often limited by the oxygen supply. The reduction in oxygen consumption per cell that occurs under hypoxic conditions may be exploited as a method for increasing reactor capacity if additional glucose is provided to offset increased glycolytic activity. The effects of oxygen deprivation on recombinant tPA (tissue‐type plasminogen activator) production were investigated using midexponential and slowly growing CHO cells. The specific oxygen consumption rate can be reduced by at least 50% (mild hypoxic conditions) without affecting the cell growth rate, maximum cell concentration, tPA production rate, or tPA quality (as characterized by the tPA‐specific activity and SDS‐PAGE analysis). This suggests that mild‐hypoxic conditions (with sufficient glucose) can be used to double the cell concentration and volumetric tPA production rate (at a constant volumetric oxygen supply rate) without sacrificing product quality. However, anoxic conditions should be avoided. When slowly growing cultures were exposed to anoxia, the tPA production rate decreased by 80% without affecting tPA quality. However, when midexponential cultures were exposed to anoxia, the drop in tPA production was accompanied by a decrease in tPA quality that ranged from a 40% decrease in tPA specific activity to extensive tPA degradation. © 1993 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260420311

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

年代:1993

数据来源: WILEY