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Improvement of glucoamylase production using axial impellers with low power consumption and homogeneous mass transfer

Paper ID Volume ID Publish Year Pages File Format Full-Text
2937 143 2015 10 PDF Available
Title
Improvement of glucoamylase production using axial impellers with low power consumption and homogeneous mass transfer
Abstract

•Enzyme yields increased significantly (20–60%) with proper agitation system.•Exceed power input of RT impeller enhanced the shear effect rather than mixing.•Pellet morphology is determined mostly by local high shear zone.•The kLa are similar in average but widely divergent in distribution in the fermentor.

Significantly influenced by complex cell morphology, glucoamylase fermentation using Aspergillus niger is characterized by high apparent viscosity and shear-thinning rheology. In this study, the influence of liquid flow field patterns on morphology, broth rheology, mass transfer and glucoamylase production was investigated by applying two different configurations with radial (Ruston Turbine, RT) and axial (Wide-blade hydrofoil upward-pumping, WHu) flow impellers. It was found that empirical correlations for averaged quantities, such as the mass transfer coefficient and viscosity, cannot reasonably explain the observations. Therefore, numerical simulation was carried out to study the detailed characteristics of local field in lab-scale bioreactors. The results showed, under similar glucose and oxygen uptake rates, that the WHu configuration formed relatively homogeneous viscosity and mass transfer fields, while the RT configuration was accompanied with significant heterogeneities. Under these conditions, the fraction of active mycelia in pellets could be highly correlated with enzyme production, and a novel parameter (Active Part Percentage, APP) was defined to introduce the effects of flow field on pelletized morphology. The WHu impellers facilitated the formation of pellets and hairy structures, with a higher APP of the pellets. As a result, the culture with the axial flow impeller configuration exhibited a larger glucoamylase production rate (+25%) and product yield on sugar (+23%) and yield on energy (+60%) in comparison to the radial flow impeller. Computational fluid models were proposed to in-depth understand such results based on local mass transfer and viscosity values, since the average values are similar over the entire fermentation processes.

Keywords
Glucoamylase; Impeller type; Aspergillus niger; Morphology analysis; CFD
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Improvement of glucoamylase production using axial impellers with low power consumption and homogeneous mass transfer
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Publisher
Database: Elsevier - ScienceDirect
Journal: Biochemical Engineering Journal - Volume 99, 15 July 2015, Pages 167–176
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us