摘要:

AbstractA generalized rate equation for formally two‐step enzymatic reaction has been derived. In this derivation the reaction rate has been regarded as a function of substrate conversion. Applications of this equation to reactor operating parameters and productivity calculations are presented and discusse

ISSN:0006-3592    

DOI:10.1002/bit.260201202

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe stability of the neutral and alkaline proteases in aBacillus subtilisenzyme mixture was studied in aqueous solutions at room temperature. Stabilization of the proteases in solution for periods up to 25 days was achieved by the addition of various protein preparations including casein and soya protein. The degree of stabilization by casein was concentration dependent to about 2% protein. The instability of the neutral protease in solutions of theB. subtilisenzyme mixture was shown to be due primarily to proteolysis by the alkaline protease since the diisopropylfluorophosphate‐treated enzyme was quite stable. Formulation of such enzyme solutions at low pH gave greater stability as did solutions containing an alkaline protease inhibitor from potatoes. A Conceptual approach to the formulation of enzyme solutions containing proteolytic enzyme to ensure maximum stability is propose

ISSN:0006-3592    

DOI:10.1002/bit.260201203

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

年代:1978

数据来源: WILEY

摘要:

AbstractA model that continuously predicts the concentration of microorganisms in complex medium fermentations is suggested. The model uses carbon dioxide evolution as its primary input and assumes that respiration activity can be differentiated into growth‐related and maintenance‐related functions. This model can be programmed on computer‐coupled vessels and used to standardize on a physiological fermentation inoculum transfer time. The cell concentration estimate can also be used to calculate specific growth rate and can be combined with additional monitored information to calculate other important fermentation parameters such as specific oxygen u

ISSN:0006-3592    

DOI:10.1002/bit.260201204

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

年代:1978

数据来源: WILEY

摘要:

AbstractComparison of the equations that describe the relationship between the maximum cell yield coefficient, the maintenance coefficient, and the specific growth rate at steady‐state conditions revealed that the equations used for axenic cultures are congruent with those commonly used for mixed‐culture system such as activated sludge. A unified basis was proposed. The expression of the yield and maintenance coefficients in carbon units according to the unified basis permitted one to evaluate literature data on both axenic and mixed‐culture systems. From this it appears that the maximum cell yield ranges from 0.50–0.80 (mg biomass carbon formed/mg substrate carbon used) for both axenic and mixed systems. However, the maintenance coefficient (mg substrate C/mg biomass C·hr) for the axenic cultures was between 0.010 and 0.100, but for activated sludge communities it was between 0.001 and 0.010. Microorganisms were isolated from sludge communities with these apparently low maintenance requirements and grown axenilly. Their maintenance coefficients but not their maximum yield coefficients decreased with decreasing specific growth rates. The consequences of this finding with regard to species selection in mixed‐culture systems and the concept of cellular maintenance requirement are

ISSN:0006-3592    

DOI:10.1002/bit.260201205

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

年代:1978

数据来源: WILEY

摘要:

AbstractConditions for the laboratory‐scale production of acetoin plus diacetyl byEnterobacter CloacaeATCC 27613 were studied. Thirty‐five g acetoin plus diacetyl/50 g sucrose were obtained when fermentation was carried out in 2. 5 liter medium containing 12.5 g peptone and 12. 5 g yeast extract, at pH 7.0, in a 5 liter conical flask on a shaker (240rpm) at 28–30°C for 48 hr. Recovery of pure diacetyl was 85% of the total plus di

ISSN:0006-3592    

DOI:10.1002/bit.260201206

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

年代:1978

数据来源: WILEY

摘要:

AbstractDispersion and mass‐transfer characteristics and fluidization parameters influencing the performance of a small pilot‐plant immobilized enzyme reactor are evaluated. The suitability of a dispersed plug‐flow model to predict the conversions obtained in the enzymatic reaction (starch → glucose) catalyzed by amyloglucosidase immobilized to solid and porous carriers is assessed. The performance of a fluidized‐bed reactor is compared on the basis of a normalized residence time with that of a fixed bed and found to be

ISSN:0006-3592    

DOI:10.1002/bit.260201207

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

年代:1978

数据来源: WILEY

摘要:

AbstractTen chitosan products were manufactured from dry shrimp hulls under differing process conditions and compared to a commercially available product. Manufacturing variables tested were: alkali versus enzymatic deproteination; acid demineralization versus no treatment; air versus nitrogen atmosphere; 5 min vs. 15 min deacetylation period: and varying the particle size of the dry starting material. Deproteination by alkali of enzymatic extraction did not substantially affect the nitrogen and ash compositions of dry chitosan samples. However, the viscosity was reduced in samples deproteinated by enzymatic hydrolysis. Elimination of the demineralization step resulted in products having 31–36% ash, as expected. Some differences in viscosity were observed between deminiralized and undemineralized samples, but on important differences in the molecular‐weight distribution of these samples were evident. Purging the reaction vessel with nitrogen resulted in chitosan preparations having higher viscosities and molecular‐weight distributions than those prepared in an air atmosphere. The degradative effect of air became more proshrimp hulls to 1 mm prior to any treatment resulted in a chitosan product of both higher viscosity and molecular weight than when ground to either 2 or 6.4 mm. Viscosity was not always a direct indicator of molecular weight, for although the presence of colloidal particles increased the viscosity of some samples, the molecular‐weight distribution after filtration was essentially the same as in other less viscous

ISSN:0006-3592    

DOI:10.1002/bit.260201208

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

年代:1978

数据来源: WILEY

摘要:

AbstractChitosan samples manufactured under different conditions were compared for effectiveness of coagulating an activated sludge suspension grown on vegetable canning wastes. Computer analysis of data from Buchner funnel filterability tests resulted in quadratic polynomial equations describing the response curves for volume of filtrate versus dosage, expressed as g/liter chitosan/100 g sludge suspended solids (SSS). The quotient of the filtrate volume and dosage at the inflection points of the equations obtained for 10 test samples and 1 commercial chitosan sample were compared to evaluate the response (effectiveness) per unit amount for each chitosan product. The product made by a standard procedure (deproteinated with 3% NaOH at 100°C for 1 hr, demineralized with 1NHCL at ambient temperature for 30 min, and deacetylated with 50% NaOH at 145–150°C under N2for 5 or 15 min) gave the best performance as a coagulating agent for this activated sludge system. Other products, including the commercial preparation, required higher dosages to achieve the same effectiveness. Products deacetylated in the presence of sir rather than nitrogen decreased waste treatment effectiveness, which approximated the trends of reduced viscosity and molecular‐weight distribution. The products containing minerals were less effective than products from which minerals had been removed prior to deacetylation, but they were more effective than the enzyme treated sample and the commercial product. In general, although chitosan products obtained after 15 min deacetylation were more effective than those receiving 5 min deacetylation, effectiveness did not correlate linearly with viscosity and molecular‐weight distribution trends. However, chitosan products deacetylated for 15 min did show that the higher‐molecular‐weight products (0.65–1.1 × 106) were more effective coagulating agents for activated sludge than the manufactured product having the lowest molecular weight (0.47 × 106) and the commercial reference sample (0.56 × 106). Thus, higher values for molecular weight were predictive of greater effectiveness for coagulation of activated sl

ISSN:0006-3592    

DOI:10.1002/bit.260201209

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

年代:1978

数据来源: WILEY

摘要:

AbstractTen chitosan products, prepared as described in part I of this study, were evaluated in jar tests that measured their effectiveness for coagulation of suspended solids and removing turbidity from cheese whey. A polynominal regression analysis was found to be useful for determining the optimal effectiveness of each chistosan preparation, and was expressed as the percent reduction on turbidity per unit concentration of chitosan added. The effectiveness of the chitosan products was found to be inversely related to their molecular‐weight values. This situation was different from the findings described in part II of this study, in which the filterability of activated sludge was tested. Enzymatic deproteination yielded chitosan products that performed better than those produced by alkali deproteination. Demineralized products were also more effective than those that had not been demineralized. The preparations deacetylated under a nitrogen atmosphere were more effective than those deacetylated in air, but this was shown to be true only for the first 5 min of deacetylation. When deacetylated for 15 min, no differences were noted. In this study, differences in performance between the various products were largely due to the differing dosages required to achieve the maximum reduction in turbidity of cheese whey, while the maximum responses achieved by the various products tested were about the same. A commercial product, which was less effective as a sludge coagulating agent in part II of this study, was more effective for cheese whey coagulation and turbidity removal than the majority of the experimental chitosan preparations teste

ISSN:0006-3592    

DOI:10.1002/bit.260201210

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

年代:1978

数据来源: WILEY

摘要:

AbstractTechnical aspects of the separation of aqueous two‐phase systems in a commercial separator were studied in detail. For the Gyrotester B, the smallest available separator, a flow rate of 200 ml/min and a length of the regulating screw in the outlet port of 13.5 mm were found as optimal operation parameters for the separation of a poly(ethylene glycol) (PEG)/dextran two‐phase system. In the presence of cells and cell debris the characteristics of the carrier two‐phase systems are changed, most notably the phase ratio. Nevertheless good separation and high throughput can be maintained up to 30% wet cell material in the complete system. Using this method the enzyme pullulanase was extracted from 6.65 kgKlebsiella pneumoniaein 88% yield in a single step in less than 2 hr. A yield of 90% was predicted for this step based upon laboratory data, indicating that the performance of the extraction and separation can be calculated with the necessary accuracy and the further scale‐up of the process should be accomplished quite easily. The hydrophilic polymers Constituting the phase system will often stabilize the enzymes, So that the separation can be carried out at room temperature without extensive cooling. The method of enzyme solubilization or cell disruption is not decisive for the successful extraction of the enzymes, the only limitation being the necessity to find a suitable two‐phase system where the desired product and the cells or cell debris will partition in opposite phases. This is shown for α‐glucosidase fromSaccharomyces carlsbergensisand three aminoacyl‐tRNA‐synthetases fromEscherichia coli. The results obtained demonstrate that aqueous two‐phase systems can be separated in commercially available separators with high capacity and efficiency. It can be expected that the advanced separation technology available from chemical engineering studies can also be used for the development of large‐scale isolation processes for enzymes involving liqu

ISSN:0006-3592    

DOI:10.1002/bit.260201211

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

年代:1978

数据来源: WILEY