Formation of composite gel fiber from cellulose acetate and zirconium tetra-n-butoxide and entrap-immobilization of β-galactosidase on the fiber

2003 ◽  
Vol 18 (3) ◽  
pp. 672-676 ◽  
Author(s):  
K. Nakane ◽  
T. Ogihara ◽  
N. Ogata ◽  
Y. Kurokawa
Keyword(s):  
Cellulose Acetate ◽  
Fiber Diameter ◽  
Fiber Surface ◽  
Lactose Hydrolysis ◽  
Phosphate Solution ◽  
Michaelis Constant ◽  
Coordination Numbers ◽  
Maximum Reaction ◽  
Composite Gel ◽  
Opposite Tendency

The formation of a composite gel fiber from cellulose acetate and zirconium tetra-n-butoxide was examined. The gel was thought to have formed by the coordination of OH and CO groups of cellulose to zirconium, taking six coordination numbers around the zirconium. The gel fiber had good stability in common solvents, phosphate solution, and electrolyte solution. Then, under mild conditions, a β-galactosidase was entrap-immobilized on it. The apparent Michaelis constant of the Immobilized β-galactosidase was larger than that of native β-galactosidase, whereas the opposite tendency was observed for the maximum reaction velocity. The activity of the immobilized β-galactosidase increased as the fiber diameter decreased. These findings indicated that lactose hydrolysis took place in the vicinity of the fiber surface. The immobilized β-galactosidase had a higher thermal stability than the native type.

scholarly journals Immobilization of Aspergillus oryzae  β-Galactosidase on Cellulose Acetate-Polymethylmethacrylate Membrane and Its Application in Hydrolysis of Lactose from Milk and Whey

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Shakeel Ahmed Ansari ◽  
Rukhsana Satar ◽  
Syed Kashif Zaidi ◽  
Abrar Ahmad
Keyword(s):  
Cellulose Acetate ◽  
Aspergillus Oryzae ◽  
Immobilized Enzyme ◽  
Product Inhibition ◽  
Lactose Hydrolysis ◽  
Batch Reactors ◽  
Maximum Reaction Rate ◽  
Maximum Reaction ◽  
Repeated Use ◽  
Physical And Chemical

The present study demonstrates the immobilization of Aspergillus oryzae β-galactosidase on cellulose acetate-polymethylmethacrylate (CA-PMMA) membrane and its application in hydrolyzing lactose in dairy industries. The effect of physical and chemical denaturants like pH, temperature, product inhibition by galactose, storage stability, and reuse number of the enzyme immobilized on CA-PMMA membrane has been investigated. Lactose was hydrolyzed from milk and whey in batch reactors at 50°C by free and immobilized β-galactosidase (IβG). Optimum pH for the free and immobilized enzyme was found to be the same, that is, 4.5. However, IβG retained greater fractions of catalytic activity at lower and higher pH ranges. The temperature optimum for the immobilized enzyme was increased by 10°C. Moreover, Michaelis-Menten constant was increased for IβG as compared to the native one while maximum reaction rate was reduced for the immobilized enzyme. The preserved activity of free and immobilized enzyme was found to be 45% and 83%, respectively, after five weeks of storage at 4°C. Reusability of IβG was observed to be 86% even after fifth repeated use, thereby signifying its application in lactose hydrolysis (as shown in lab-scale batch reactors) in various dairy products including milk and whey.

scholarly journals A Novel Sucrose Isomerase Producing Isomaltulose from Raoultella terrigena

2021 ◽  
Vol 11 (12) ◽  
pp. 5521
Author(s):  
Li Liu ◽  
Shuhuai Yu ◽  
Wei Zhao
Keyword(s):  
Ph Value ◽  
Wild Type ◽  
Michaelis Constant ◽  
Wild Type Enzyme ◽  
Maximum Reaction Rate ◽  
E Coli ◽  
Maximum Reaction ◽  
Conversion Rates ◽  
Raoultella Terrigena ◽  
Sucrose Isomerase

Isomaltulose is widely used in the food industry as a substitute for sucrose owing to its good processing characteristics and physicochemical properties, which is usually synthesized by sucrose isomerase (SIase) with sucrose as substrate. In this study, a gene pal-2 from Raoultella terrigena was predicted to produce SIase, which was subcloned into pET-28a (+) and transformed to the E. coli system. The purified recombinant SIase Pal-2 was characterized in detail. The enzyme is a monomeric protein with a molecular weight of approximately 70 kDa, showing an optimal temperature of 40 °C and optimal pH value of 5.5. The Michaelis constant (Km) and maximum reaction rate (Vmax) are 62.9 mmol/L and 286.4 U/mg, respectively. The conversion rate of isomaltulose reached the maximum of 81.7% after 6 h with 400 g/L sucrose as the substrate and 25 U/mg sucrose of SIase. Moreover, eight site-directed variants were designed and generated. Compared with the wild-type enzyme, the enzyme activities of two mutants N498P and Q275R were increased by 89.2% and 42.2%, respectively, and the isomaltulose conversion rates of three mutants (Y246L, H287R, and H481P) were improved to 89.1%, 90.7%, and 92.4%, respectively. The work identified a novel SIase from the Raoultella genus and its mutants showed a potential to be used for the production of isomaltulose in the industry.

On the Cooling of Fibers

1983 ◽  
Vol 105 (4) ◽  
pp. 830-834 ◽  
Author(s):  
A. Moutsoglou
Keyword(s):  
Melt Spinning ◽  
Fiber Diameter ◽  
Fiber Surface ◽  
Subsequent Increase ◽  
Boundary Layer Equations ◽  
Axial Temperature ◽  
Spinning Process ◽  
Radiative Losses ◽  
Filament Surface ◽  
Local Speed

The effects of the stretching of filaments on the cooling of fibers during the melt-spinning process are studied numerically. The filament is modeled as a continuous, cylindrical cone that moves steadily through an otherwise quiescent environment, with its diameter attenuating exponentially. Radiative cooling from the fiber surface is also accounted for in the analysis. The buoyancy-affected laminar and turbulent boundary layer equations are solved by a finite difference scheme, to determine the axial temperature variation of the filament. It is found that the reduction of the fiber diameter and the subsequent increase in the local speed of the filament enhances greatly the cooling from the filament surface, whereas the increase of the cooling due to radiative losses is not significant for all the flow cases considered.

FLEXURAL PROPERTIES OF INJECTION-MOLDED BAMBOO/PBS COMPOSITES

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2838-2843 ◽  
Author(s):  
KAZUYA OHKITA ◽  
HITOSHI TAKAGI
Keyword(s):  
Flexural Strength ◽  
Natural Fiber ◽  
Flexural Modulus ◽  
Fiber Surface ◽  
Flexural Properties ◽  
Pull Out ◽  
Polybutylene Succinate ◽  
Injection Molded ◽  
Bamboo Powder ◽  
Opposite Tendency

In recent years, from an environmental perspective, there has been increasing interest in the change to a sustainable society. The use of natural-fiber-reinforced biodegradable composites has been proposed as one solution. Bamboo is an often used renewable bio-resource; it has an inherent advantage of rapid growth. Polybutylene succinate ( PBS ), used as matrix resin, has biodegradable characteristics. This paper describes flexural properties of bamboo/ PBS composites prepared by injection molding. The following results were obtained. The flexural modulus was improved with increasing bamboo powder contents when the cylinder temperature of the injection molder was 140°C. However, the flexural strength showed the opposite tendency to be decreased with increasing bamboo powder contents. An SEM photomicrograph of the fracture surface for bamboo/ PBS composites showed typical fracture behavior of pull-out fibers without fiber fracture. Furthermore, there was no adhesion of PBS resin on the bamboo fiber surface. Processing conditions affected mechanical properties of bamboo/ PBS composites, imparting higher flexural strength and flexural modulus at high cylinder temperatures such as 180°C and 200°C.

Effect of Heat and Wet Treatment on the Strength of PLA Fiber

2010 ◽  
Vol 152-153 ◽  
pp. 1253-1257
Author(s):  
Shao Wei Wang ◽  
Yi Zhang ◽  
Hua Wu Liu
Keyword(s):  
Fiber Diameter ◽  
Fiber Surface ◽  
Measured Temperature ◽  
Acidic Environment ◽  
Fiber Damage ◽  
Before And After ◽  
Hydrolysis Of

Before and after heat and wet treatment, the fineness and strength of PLA sample fibers were measured. Temperature, rather than moisture, was reckoned the major factor weakening the strength and fineness of PLA fiber. Acidic and alkali environments activated the hydrolysis of the fiber and lead to obvious fiber damage. Compared with the acidic environment, alkali condition resulted in far faster hydrolysis, caused more reduction of fiber diameter and strength. In addition, vertical cracks appeared on the fiber surface in alkali conditions, but did not occur in acidic environment. Finally, it was found that heat and wet treatment in a neutral environment did not make obvious harm to PLA fiber.

Why so much oestriol? A comparison of the aromatisation of androstenedione and 16α-hydroxyandrostenedione when incubated alone or together with human placental microsomes

1996 ◽  
Vol 148 (3) ◽  
pp. 399-407 ◽  
Author(s):  
Y S H Othman ◽  
R E Oakey
Keyword(s):  
Potent Inhibitor ◽  
Fetal Liver ◽  
Late Pregnancy ◽  
Dehydroepiandrosterone Sulphate ◽  
Michaelis Constant ◽  
Maximum Reaction ◽  
Pregnancy Urine ◽  
Analogous Experiment ◽  
Excretion Rates

Abstract Estimates of the relative abundance of 16α-hydroxy- and 16-deoxyoestrogens in late pregnancy urine lie between 13:1 and 5:1, yet the ratio of the concentrations of the major precursors 16α-hydroxydehydroepiandrosterone sulphate and dehydroepiandrosterone sulphate in cord blood is about 2·5:1. This discrepancy might imply that 16α-hydroxy-C19 steroids are used more efficiently for placental oestrogen biosynthesis than are the 16α-deoxy-C19 steroids. On testing this hypothesis by incubation of placental microsomes with 16α-hydroxy- and 16-deoxy- precursors together (concentration ratios 128:1 to 1:1), initial rates of oestrogen formation were highest from the 16-deoxy-C19 steroid. Additionally, whilst each substrate appeared to inhibit the aromatisation of the other, the 16-deoxy-C19 steroid was the more potent inhibitor. These findings were supported by an analogous experiment with placental slices. When each precursor was examined separately with microsomes from 4 placentae, aromatisation of the 16α-hydroxy-C19 steroid (Michaelis constant, (Km) 0·75–1·24 μmol/l, maximum reaction velocity (Vmax) 28–69 pmol product/min/mg protein) was less efficient than that of the 16-deoxy-C19 steroid (Km 0·10–0·15 μmol/l, Vmax 71–145 pmol product/min/mg protein). To reconcile the disparity between the measured utilisation of precursors in vitro and expectations drawn from precursor availability and urinary excretion rates, sources of urinary 16α-hydroxyoestrogens additional to placental aromatisation need to be considered. Hydroxylation of 16-deoxyoestrogens (the phenolic pathway) appears limited but aromatisation in fetal liver of 16α-hydroxyandrostenedione not utilised by the placenta appears to be worth attention. Journal of Endocrinology (1996) 148, 399–407

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