摘要:

AbstractPermeabilities of several solutes through the composite membranes containing phospholipids have been measured. They were inversely proportional to the content of the phospholipids in the membrane. Both the permeability of solutes and the degree of permeability change around the phase transition temperature of the phospholipids for the hydrophobic solutes such asn‐butanol and salicylamide were larger than those for the hydrophilic solutes such as amino acids and pyridoxine. These results suggest thatthe permeation path of hydrophobic solutes is different from that of hydrophilic ones. The addition of phosphatidyl ethanolamine, phosphatidyl serine, or phosphatidic acid to the composite membrane influenced the solute permeability due to the introduced negative charge and/or the change in the molecular packing of phospholipi

ISSN:0006-3592    

DOI:10.1002/bit.260280102

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

年代:1986

数据来源: WILEY

摘要:

AbstractA laboratory investigation has been undertaken to asses the effects of two operating parameters, mean cell residence time (MCRT) and anoxic hydraulic retention time (HRT), on the performance of an anoxic/oxic activated sludge system. The performance of the system was evaluated in terms of its COD, nitrogen, and biomass characteristics. An activated sludge system is capable of producing a better effluent, in terms of COD and nitrogen characteristics, when it is operated in an anoxic/oxic fashion. A longer MCRT and an adequate anoxic HRT are desirable in the operation of an anoxic/oxic activated sludge system. For the wastewater used in this investigation, the anoxic/oxic unit was capable of producing an effluent with the following characteristics when it was operated at MCRT = 20 days, total system HRT = 10 h, and anoxic HRT = 3–5 h: COD = 15 mg/L; VSS = 10 mg/L; TKN = 1.30 mg/L; NH3− N = 0.60 mg/L; and NO2+ NO3− N = 5.0 mg/L. A uniform distribution of biomass is achievable in an anoxic/oxic activated sludge system because of the intensive recirculation/convection maintained. The provision of an anoxic zone in the aeration tank promotes a rapid adsorption of feed COD into the biomass without an immediate utilization for cell synthesis. This, in turn, results in a high microbial activity and a lower observed biomass yield in the system. A tertiary treatment efficiency is achievable in an anoxic/oxic activated sludge system with only secondary treatment operations and costs. A conventional activated sludge system can be easily upgraded by converting to the anoxic/oxic operation with minor process modifica

ISSN:0006-3592    

DOI:10.1002/bit.260280103

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

年代:1986

数据来源: WILEY

摘要:

AbstractA method is described using fast protein liquid chromatography (FPLC) for the monitoring of protein formation during fermentation. The procedure consists of centrifugation to recover the cells, sonication of the cells, centrifugation to remove cell debris, and analysis of supernatant on a column of Mono Q (a strong anion exchanger). Analysis of peak areas provides quantitative determination of product concentration. Maintenance and life of the Mono Q column is discussed. We find that FPLC is a convenient method for measuring products in cell homogenates because it gives rapid, highly resolved separations.

ISSN:0006-3592    

DOI:10.1002/bit.260280104

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

年代:1986

数据来源: WILEY

摘要:

AbstractBiosorption of uranium and lead by lyophilized cells ofStreptomyces longwoodensiswas examined as a function of metal concentration, pH, cell concentration, and culture age. Cells harvested from the stationary growth phase exhibited an exceptionally high capacity for uranium (0.44 g U/g dry weight) at pH 5. Calculated values of the distribution coefficient and separation factor indicated a strong preference of the cell mass for uranyl ions over lead ions. The specific uranium uptake was similar for the cell wall and the cytoplasmic fraction. Uranium uptake was associated with an increase in hydrogen ion concentration, and phosphorus analysis of whole cells indicated a simple stoichiometric ratio between uranium uptake and phosphorus content. It is proposed that metal ions are bound to phosphodiester residues present both in the cell wall and cytoplasmic fractions. Based on this model, it was shown that uranium accumulation exhibits a maximum at pH 4.6 that is supported by experimental data from previous investigations.

ISSN:0006-3592    

DOI:10.1002/bit.260280105

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

年代:1986

数据来源: WILEY

摘要:

AbstractA separate role for water activity in the conversion of sugars to ethanol by two strains of yeast is identified. During fermentation of both single and mixed sugar substrates, the water activity was shown to remain constant during the logarithmic growth phase. This is despite the changes in concentration of substrates and product, the constancy reflecting the fact that the greater influence of ethanol on the solution activity is counterbalanced, in the early stages of the fermentation, by its low yield. The end of the log phase of growth coincides with the start of a period of gradually decreasing water activity. For the more ethanol‐tolerant strain UQM66Y, growth was found to cease at a constant value of water activity while that for the less tolerant strain UQM70Y depended on both ethanol concentration and water activity. It is argued that water activity is a more appropriate variable than ethanol concentration for describing some of the nonspecific inhibitory effects apparent in ethanol fermentations. A straightforward method for the calculation of water activity during such fermentations based on the use of solution osmolality is presente

ISSN:0006-3592    

DOI:10.1002/bit.260280106

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

年代:1986

数据来源: WILEY

摘要:

AbstractContinuous cellulase production byTrichoderma virideQM 9123, immobilized in 6 mm diameter, spherical, stainless steel biomass support particles, has been achieved using a medium containing glucose as the main carbon source. Experiments were carried out in a 10‐L spouted bed fermentor. In this type of reactor‐recycled broth is used to create a jet at the base of a bed of particles, causing the particles to spout and circulate. During the circulation, particles pass through a region of high shear near the jet inlet. This effectively prevents a buildup of excess biomass and thus enables steady‐state conditions to be achieved during continuous operation. Continuous production of cellulase was achieved at significantly higher yield and productivity than in conventional systems. At a dilution rate of 0.15 h−1(nominal washout rate for freely suspended cells is 0.012 h−1), the yield of cellulase on glucose was 31% higher than that measured during batch operation, while the volumetric productivity (31.5 FPA U/L· h) was 53% greater than in the batch system. The specific cellulase productivity of the immobilized cells was more than 3 times that of freely suspended cells, showing that diffusional limitations can be beneficial. This offers significant opportunity for the further development of biomass support particles and associated b

ISSN:0006-3592    

DOI:10.1002/bit.260280107

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

年代:1986

数据来源: WILEY

摘要:

AbstractPoly(maleic anhydride styrene) graft copolymers of cellulose, pectin polygalacturonic acid salt, calcium polygalacturonate, and starch were prepared and used to immobilize proteins. The cellulose grafts coupled quite appreciable quantities of acid phosphatase, glucose oxidase, and trypsin. However, the general retention of activity was somewhat disappointing. Further investigation with acid phosphatase showed that the amount of enzyme immobilized increased as the amount of anhydride in the graft copolymer increased but no such relationship existed for the enzymic activity. The cellulose graft copolymers were hydrolyzed and it appeared that the carboxyl group aided adsorption of the enzyme. Attempts to couple acid phosphatase using CMC through the free carboxyl groups, created by hydrolysis, gave only a small increase in the extent of protein coupling. However, the unhydrolyzed system gave a useful degree of immobilization of cells ofBacillus stearothermophilus, as did a poly(maleic anhydride/styrene)‐cocellulose system. Attempts to improve the activity by using grafts based on other polysaccharide supports met with mixed success. Pectin products were soluble. Polygalacturonic acid products were partially soluble and extremely high levels of enzymic activity were obtained. This was probably due in part to the hydrophilic nature of the system, which also encouraged absorption of the enzyme. Attempts were made to reduce the solubility by using the calcium pectinate salt. Immobilization of acid phosphatase and trypsin resulted in inceased protein coupling but relatively poor activities were attained. A starch based system gave similar results. Calcium polygalacturonate was used to prepare an insoluble graft copolymeric system containing acrylonitrile‐comaleic anhydride. The resulting gels gave excellent coupling with acid phosphatase which had a very good retention of activ

ISSN:0006-3592    

DOI:10.1002/bit.260280108

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

年代:1986

数据来源: WILEY

摘要:

AbstractUrokinase (UK) has been immobilized to the inner surfaces of fibrocollagenous tubes (FCT) in an attempt to develop a fibrinolytic biomaterial which may be suitable for use as a small diameter vascular prosthesis. The enzyme was bound by adsorption followed by glutaraldehyde crosslinking. Anin virtokinetic study of immobilized urokinase was conducted by employing the tubular material as a flow through reactor operated in a batch recycle mode in which the esterolysis of the model substrate,N‐α‐acetyl‐L‐lysine methyl ester (ALME), was monitored as a function of substrate concentration, recycle flow rate, and temperature. Results were compared with data from the soluble enzyme reaction, which was conducted in the presence and absence of 10% swine skin gelatin, in order to identify the specific effects of a collagenous microenvironment. Observed rates for the UK‐FCT catalyzed reaction were observed to be dependent on recycle flow rates below 12 mL/min (Re = 107). Apparent Michaelis–Menten rate parameters were determined by a nonlinear search technique for two flow rates: one above the critical point for external diffusion effects (Re = 282) and one within the mass‐transfer‐limited region (Re = 71). When the latter data were corrected for external diffusion by applying the Graetz correlation for laminar flow in tubes to estimate themass transfer coefficient, the correctedKmof 6.45 ± 0.38 mMagreed very closely with the diffusion free parameter (i.e. 6.13 ± 0.63). Furthermore, this value was observed to be an order of magnitude higher than that of the soluble enzyme but approximately equal to theKmof the soluble enzyme in a 10% gelatin environment (8.13 ± 1.53 mM). It is postulated that the difference in kinetic parameters between soluble and collagen immobilized UK is due to an inherent interaction between collagen and enzyme rather than to mass transfer effects. Such aninteraction is supported by the effects of collagen on thermal stability and e

ISSN:0006-3592    

DOI:10.1002/bit.260280109

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

年代:1986

数据来源: WILEY

摘要:

AbstractUrokinase was immobilized by entrapment to fibrocollagenous tubes in order to develop a small‐caliber fibrinolytic vascular prosthesis. Several parameters associated with the immobilization process were studied in order to optimize bound urokinase activity and stability. A total of 37% of the absorbing enzyme was attached to the collagen tube and 38% of the attached enzyme retained esterolytic activity, under optimal conditions. In the crosslink step of the entrapment process, the glutaraldehyde concentration was varied from 0.01 to 5.00% (i.e., 0.01, 0.1, 1.0, 3.0, and 5.0%). Urokinase activity was optimized at a 1.0% glutaraldehyde crosslink concentration. Urokinase‐bound fibrocollagenous tubes (UK‐FCT) prepared at the above glutaraldehyde concentrations were tested for their activity with time. The UK‐FCT's with 0.1, 1.0, and 3.0% glutaraldehyde retained constant activity for at least 75 h operation time. The UK‐FCT's with 0.1, 1.0, and 3.0% glutaraldehyde retained constant activity for at least 75 h operation time. The UK‐FCT's with 5.0 and 0.01% glutaraldehyde remained stable for the first 50 h operation time, but begandeactivating beyond 50 h. UK‐FCT'S Crosslinked with 0.01, 0.1, 1.0, and 5.0% glutaraldehyde were recrosslinked with 0.02% glutaraldehyde for 24 h, after they have been operating for 50 h, and the effect of reexposing the crosslink agent on the stability of the UK‐FCT's was studied. The results showed that 0.02% glutaraldehyde reexposure had no effect on 0.1, 1.0, and 5.0% glutaraldehyde crosslinked UK‐FCT's but exerted an inhibitory effect on a 0.01% crosslink density UK‐FCT. Several fibrocollagenous tubes were exposed to various glutaraldehyde concentrations prior to immobilizing urokinase. The subsequent immobilization process occurred under optimal conditions. The effect of the precrosslink step on the activity of the UK‐FCT was studied. Results indicated that UK‐FCT activity decreases as the precrosslink density increases. The UK‐FCT's made under optimal conditions remained stable for at least 75 h operation time, corresponding to ca.1 year of storage time.Ex vivoexposure of UK‐FCT's to whole canine blood did not affect catalytic activity. Implantation of a UK‐FCT by carotid arterial interposition via an end‐to‐end anastomosis and subsequent excision after 60 days resulted in an enhanced esterolytic activity which decreased with time to a l

ISSN:0006-3592    

DOI:10.1002/bit.260280110

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

年代:1986

数据来源: WILEY

摘要:

AbstractThe kinetic properties ofSaccharomyces cerevisiaeimmobilized on crosslinked gelatin were found to be substantially different from those of the suspended yeast. Batch fermentation experiments conducted in a gradientless reaction system allowed comparison of immobilized cell and suspended cell performance. The specific rate of ethanol production by the immobilized cell was 40–50% greater than for the suspended yeast. The immobilized cells consumed glucose twice as fast as the suspended cells, but their specific growth rate was reduced by 45%. Yields of biomass from the immobilized cell population were lower at one‐third the value for the suspended cells. Cellular composition was also affected by immobilization. Measurements of intracellular polysaccharide levels showed that the immobilized yeast stored larger quantities of reserve carbohydrates and contained more structural polysaccharide than did suspended cells. Flow cytometry was used to obtain. DNA, RNA, and protein frequency functions for immobilized and suspended cell populations. These data showed that the immobilized cells have higher ploidy than cells in suspension. The observed changes in immobilized cell metabolism and composition may have arisen from disturbance to the yeast cell cycle by the cell attachment, causing alterations in the normal pattern of yeast bud development, DNA replication, and synthesis of cell wall compone

ISSN:0006-3592    

DOI:10.1002/bit.260280111

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

年代:1986

数据来源: WILEY