Improved biocatalyst effectiveness by controlled immobilization of enzymes

Borchert, Axel; Buchholz, Klaus

doi:10.1002/bit.260260715

Cited by 39 publications

(21 citation statements)

References 11 publications

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“…In consequence, a less active enzyme derivative was obtained when a very high enzyme load was offered. This hypothesis is supported by studies showing that the higher the enzyme concentrations in the immobilization solution, the more enzyme molecules are immobilized in the more external layers of the support, leading to more heterogeneous distributions of the immobilized enzyme [17]. Nevertheless, another possible explanation would be the presence of some additive(s) in the enzyme solution that can react with the aldeyde groups of the support.…”

Section: Preparation Of the Biocatalyst Aiming At Increasing Enzyme Cmentioning

confidence: 79%

Improving the Performance of a Continuous Process for the Production of Ethanol from Starch

Trovati

Giordano

2009

Appl Biochem Biotechnol

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In a previous work, a continuous simultaneous saccharification and fermentation process to produce ethanol from cassava starch was studied, using a set of fixed-bed reactors. The biocatalyst consisted of glucoamylase immobilized in silica particles and co-immobilized with S. cerevisiae in pectin gel. Using 3.8 U mL(-1) (reactor) and 0.05 g(wet yeast) mL(-1) (reactor) at start-up, starch hydrolysis was the rate-limiting step. Maximum ethanol productivity was 5.8 g(ethanol) L(-1) h(-1), with 94.0% conversion of total reducing sugars (TRS) and 83.0% of the ethanol theoretical yield. In this work, the molar mass of the substrate and the biocatalyst particle size were reduced in an attempt to improve the bioreactor performance. The diameters of silica and pectin gel particles were reduced from 100 mum and 3-4 mm, respectively, to 60 mum and 1-1.5 mm, and the degree of substrate prehydrolysis by alpha-amylase was increased. The bioreactor performance was assessed for different loads of immobilized glucoamylase (2.1, 2.8, and 3.8 U mL(-1) (reactor)), for the same initial cell concentration (0.05 g(wet yeast.)mL(-1) (reactor)). Feeding with 154.0 g L(-1) of TRS and using 3.8 U mL(-1) (reactor), fermentation became the rate-limiting step. Productivity reached 11.7 g L(-1) h(-1), with 97.0% of TRS conversion and 92.0% of the ethanol theoretical yield. The reactor was operated during 275 h without any indication of destabilization.

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Section: Preparation Of the Biocatalyst Aiming At Increasing Enzyme Cmentioning

confidence: 79%

Improving the Performance of a Continuous Process for the Production of Ethanol from Starch

Trovati

Giordano

2009

Appl Biochem Biotechnol

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“…Attempts to simulate the observed kinetics with known models (Helffrich 1959;Buchholz 1979;Borchert and Buchholz 1984) were unsuccessful. Therefore an empirical approach was chosen by analysing experimental data similar to a reaction and determining apparent orders or reaction.…”

Section: Methodsmentioning

confidence: 99%

“…Attempts to analyse the experimental results with known kinetic approaches (c. f. Helffrich 1959; Buch- Borchert and Buchholz 1984) were not successful. Therefore a first order reaction was taken as an attempt to simulate the data (Fig.…”

Section: Adsorption Kineticsmentioning

confidence: 99%

Investigations on cephalosporin C adsorption kinetics and equilibria

Hicketier¹,

Buchholz

1990

Appl Microbiol Biotechnol

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The kinetics and equilibria of cephalosporin C adsorption on different commercial adsorbents were investigated. Adsorption isotherms could be analysed according to the Brunauer, Emmett and Teller theory. For the interpretation of adsorption kinetics it was necessary to develop a more complex model comprising both a rapid and a slower step. An integrated approach combining kinetics and equilibria allowed for simulation of the experimental data and can be used as a basis for predicting technical approaches such as fluidized-bed technology.

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“…Moreover, the distribution of the enzyme inside the support is most important for the catalytic effectiveness of the immobilized enzyme and can also influence the stability of the biocatalyst (Hossain and Do, 1987). This distribution is the final result of the immobilization conditions employed (Borchert and Buchholz, 1984). In the case of immobilized enzymes, the distribution of the catalytic activity is usually nonuniform when the concentration of enzyme inside the particle is relatively low (the support is not saturated with enzyme).…”

Section: Introductionmentioning

confidence: 99%

“…A shell distribution of the active catalyst reduces the real radius of the particle to the thickness of the shell, so effectiveness losses due to mass transport of substrate towards the immobilized enzyme molecules are reduced. The catalytic performance of immobilized enzymes can be improved by controling the immobilization conditions, which determines the enzyme distribution (Borchert and Buchholz, 1984). The final optimization of the biocatalysts could be performed when the effect of every variable of the immobilization process is understood, so both the distribution of the enzyme and the binding of the enzyme to the support should be controlled.…”

Section: Introductionmentioning

confidence: 99%

Diffusion and chemical reaction rates with nonuniform enzyme distribution: An experimental approach

Ladero¹,

Santos²,

Garcı́a-Ochoa³

2001

Biotechnol. Bioeng.

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The study of the effects of nonuniform distributions of immobilized β‐galactosidase on the overall reaction rate of the hydrolysis of lactose are presented. Diffusion inside the particles has been characterized by measuring the diffusion rates of two β‐galactosidase substrates: lactose and ONPG in a commercial silica‐alumina support. Effective diffusivities have been determined by the chromatographic method under inert conditions. The results obtained for tortuosity can be explained assuming that the transport only takes place in the macropores. The distribution of the immobilized enzyme has been measured by means of confocal microscopy technique. The enzyme has been tagged with FITC and immobilized in particles of different diameters, the internal local concentrations of the enzyme have been determined with the aid of an image computer program. As expected, a more nonuniform internal profile of the enzyme was found when the particle diameter was bigger. Experiments under reaction conditions were carried out in batch reactors using lactose and ONPG as substrates and particles of the immobilized β‐galactosidase of different diameter (1 · 10−4 to 5 · 10−3 m) as catalyst, employing a temperature of 40°C for lactose and 25 and 40°C for ONPG, respectively. The mass balance inside the particle for the substrates has been solved for the internal profiles of the immobilized enzyme inside particles of different size and the enzymatic reactions considered. The calculated and the experimental effectiveness factor values were similar when particles under 2.75 · 10−3 m in diameter were employed. For the same Thiele modulus, a particle with nonuniform distribution of enzyme showed a higher effectiveness as a catalyst than particles with a more uniform distribution. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 72: 458–467, 2001.

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Improved biocatalyst effectiveness by controlled immobilization of enzymes

Cited by 39 publications

References 11 publications

Improving the Performance of a Continuous Process for the Production of Ethanol from Starch

Improving the Performance of a Continuous Process for the Production of Ethanol from Starch

Investigations on cephalosporin C adsorption kinetics and equilibria

Diffusion and chemical reaction rates with nonuniform enzyme distribution: An experimental approach

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