摘要:

AbstractA high biomass concentration (19.9 g/L) was obtained with the fed‐batch cultivation ofCellulomonason pretreated sugarcane bagasse pith. Similar results in biomass concentration, yield, and substrated consumption were obtained with the discontinuous feed of bagasses as with discontinuous feed supplemented with a partial continuous addition of salts. Two or more growth phases were detected, probably caused by the differential utilization of bagasse components. An acceptably low content of bagasse components remained in the biomass after separatio

ISSN:0006-3592    

DOI:10.1002/bit.260270202

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

年代:1985

数据来源: WILEY

摘要:

AbstractGallic acid esters ofn‐propyl and amyl alcohols have been produced by enzymatic synthesis in organic solvents using immobilized tannase. Studies indicate that maximum esterification of gallic acid occurs with amyl alcohol. The enzyme shows broad alcohol specificity. However, the enzyme exhibits absolute specificity for the acid portion of the ester. Studies were carried out onKm,Vmax, pH, and temperature optim

ISSN:0006-3592    

DOI:10.1002/bit.260270203

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe aqueous effluent generated by the Fischer‐‐Tropsch process, containing a total of 13 g/L C2–C5monocarboxylic acids, was investigated as a potential substrate for the production of single‐cell protein (SCP). A bacterial isolate,Acinetobacter calcoaceticus, could utilize all the acids in the effluent simultaneously in chemostat cultures, and no residual acids were detected in the culture below a dilution rate of 0.78 h−1. The critical dilution rate was 1.04 h−1. The maintenance energy requirement of the cells growing on the monocarboxylic acid mixture was considerably lower than that of cells growing on acetate as the sole carbon source. Enrichment of the effluent with ethanol to increase the biomass concentration was successful and still allowed the simultaneous and efficient utilization of all the carbon sources, but resulted in a decrease of the critical dilution rate

ISSN:0006-3592    

DOI:10.1002/bit.260270204

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe amplification of a substrate cycle system with reversible closed reaction of two substrates was represented by mathematical equations. The results are summarized as follows: the amplification was affected especially by the affinity of enzyme and substrate, by the rate constant in rate‐limiting reaction step, and by the saturation degree of enzyme by substrate. These amplifications were not simply determined by the values ofKmandVmax, because each rate parameter in the system can affect the degree of amplification independently. The conclusion is that the “apparent” equilibrium constant of this system cannot be uniquely estimated from only data ofKmandVmaxeven if the reaction occurs in a closed s

ISSN:0006-3592    

DOI:10.1002/bit.260270205

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

年代:1985

数据来源: WILEY

摘要:

AbstractDried spheres made from an alginate solution containing magnetite particles have excellent potential as a support for enzyme immobilization and chromatographic applications. The beads were found to be much stronger than gels such as polyacrylamide and dextran, indicating that high flow rates and pressures could be used in column separations. The support withstood not only temperatures of up to 120°C, but also most pH values and common solvents. While some solutions, such as phosphate buffers, dissolved the spheres, stabilization with Tyzor TE® eliminated this problem. The physical properties of the beads include a glasslike density of 2.2 g/mL, excellent sphericity, low porosity, and a narrow size distribution. The magnetite present in the support allows the beads to be used for magnetic separations such as high gradient magnetic filtration. Their high degree of microroughness provides a large exposed surface area for enzyme and ligand binding. MixedActinomyces fradiaeproteases andAspergillus nigerα‐amylase, two enzymes representative of classes which attack large substrates, were immobilized on the bead's surface with high activity and stability. A cyanuric dye which can be used in chromatographic applications (Cibacron Blue F3GA®) was also readily coupled to the surface of this support with good yield. The support should have a wide range of applications in bioseparation and immobilized biochemical techn

ISSN:0006-3592    

DOI:10.1002/bit.260270206

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

年代:1985

数据来源: WILEY

摘要:

AbstractAn improved membrane has been developed for the microencapsulation of islets of Langerhans which protects these cells from the immune system. These requirements were accomplished through the optimization of important microencapsulation parameters and through the improved biocompatibility of a new alginate‐poly‐l‐lysine (PLL)–alginate capsule membrane. Spherical and smooth microcapsules could be formed by utilizing a purer sodium alginate and by keeping the viscosity of the sodium alginate solution above 30 cps. The strength of the capsule membrane was enhanced by increasing the alginate–PLL reaction time as well as the PLL concentration. The permeability of the membrane [4 μm thick, 93% (w/w) water] was a function of the viscosity average molecular weight (Mv) of the PLL (Mv= 4000−4 × 105) used in the encapsulation procedure. Microcapsules prepared with PLL withMv= 1.7 × 104were the least permeable, being impermeable to normal serum immunoglobulin, albumin, and haemoglobin. The microencapsulation procedure, by protecting transplanted tissue from the components of the immune system, has great clinical potential as a new form of treatment for diseases such as diabetes and

ISSN:0006-3592    

DOI:10.1002/bit.260270207

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe physiological activity of microorganisms in environments with low dissolved oxygen concentrations often differs from the metabolic activity of the same cells growing under fully aerobic or anaerobic conditions. This article describes a laboratory‐scale system for the control of dissolved oxygen at low levels while maintaining other parameters, such as agitator speed, gas flowrate, position of sparger outlet, and temperature at fixed values. Thus, it is possible to attribute in dilute nonviscous fermentations all physiologic changes solely to changes in dissolved oxygen. Experiments were conducted withAzotobacter vinelandiiandEscherichia coli. Critical oxygen concentrationsfor growth(that value of oxygen allowing growth at 97% of μmax) were measured as 0.35 ± 0.03 mg/L forA. vinelandiiand 0.12 ± 0.03 mg/L forE. coli.These values are significantly different from the commonly quoted values for critical oxygen concentrationsbased on respiration rates. Because of the superior dissolved oxygen control system and an improved experimental protocol preventing CO2limitation, we believe that the values reported in this work more closely represent rea

ISSN:0006-3592    

DOI:10.1002/bit.260270208

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

年代:1985

数据来源: WILEY

摘要:

AbstractPlasmid propagation in populations of unstable, binary fission recombinant organisms has been studied using a segregated, population balance mathematical model. Segregated models have the advantage of direct incorporation of basic information on mechanisms and kinetics of plasmid replication and segregation at the single‐cell level. The distribution of cellular plasmid content and specific rates of plasmid gene expression have been obtained for several single‐cell models of plasmid replication, partition, and gene expression. Plasmid replication kinetics during cell growth significantly influence the plasmid content distribution. In the case of transient growth of plasmid‐containing and plasmid‐free cells in partially selective medium, the degree of selection required for stable maintenance of plasmid‐containing cells has been determined. Guidelines are presented for applicability of simpler, nonsegregated models and for evaluation of the parameters in these models based on single‐cell mechanisms and associated

ISSN:0006-3592    

DOI:10.1002/bit.260270209

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

年代:1985

数据来源: WILEY

摘要:

AbstractLactate oxidase was used in combination with an electrochemical dissolved oxygen sensor to measureL‐lactate concentration in the physiological saline solution. The rate of oxygen consumption was found to have an excellent linear relationship with the lactate concentration on a log‐log scale in the lactate concentration range of 0.3–25 mM. This detection does not require additional reagents and can be developed into a simple method ofL‐lactate determination. The effects of the temperature and pH of the solution on the reaction rate were investigated and di

ISSN:0006-3592    

DOI:10.1002/bit.260270210

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

年代:1985

数据来源: WILEY

摘要:

AbstractHemicellulosic sugars, predominantly D‐xylose, comprise about one‐half the total carbohydrate that can be obtained from hardwoods and agricultural residues through dilute acid hydrolysis. Because rates and yields in the xylose fermentation are low, economic utilization of these materials as fermentation feedstocks is difficult.Pachysolen tannophilusformed 5.5% ethanol from 12% glucose but only 2% ethanol from 12% xylcose. Aeration doubled the specific rate ofD‐glucose fermentation byP. tannophilus, as compared to anaerobic fermentation, but the specific rate of the xylose fermentation remained unchanged. Periodic additions of 0.5%D‐glucose to aerobic fermentations of 3% xylose increased the yield of ethanol from 0.28 g/g xylose to greater than 0.41 g/g xylose utilized. The rate of xylose utilization remained unchanged, and radiotracer studies showed that addition of 0.5% glucose did not inhibit xylose utilization under aerobic or anaerobic conditions. No enhancement was observed anaerobically, nor was enhancement observed with acid hydrolysates, apparently because of the presence of acetic acid which inhibited growth and ferme

ISSN:0006-3592    

DOI:10.1002/bit.260270211

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

年代:1985

数据来源: WILEY