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Stochastic exposure to sub-lethal high temperature enhances exopolysaccharides (EPS) excretion and improves Bifidobacterium bifidum cell survival to freeze–drying

Paper ID Volume ID Publish Year Pages File Format Full-Text
3157 153 2014 10 PDF Available
Title
Stochastic exposure to sub-lethal high temperature enhances exopolysaccharides (EPS) excretion and improves Bifidobacterium bifidum cell survival to freeze–drying
Abstract

•Bifidobacteria viability is improved in a two-compartment scale-down reactor with sub-lethal heat stress.•Mild heat stress induces EPS overproduction.•EPS protects cells from freeze drying stress.•The method has a high scalability potential.

Exposure of microbial cells to sub-lethal stresses is known to increase cell robustness. In this work, a two-compartment bioreactor in which microbial cells are stochastically exposed to sub-lethal temperature stresses has been used in order to investigate the response of the stress sensitive Bifidobacterium bifidum THT 0101 to downstream processing operations. A stochastic model validated by residence time distribution experiments has shown that in the heat-shock configuration, a two-compartment bioreactor (TCB) allows the exposure of microbial cells to sub-lethal temperature of 42 °C for a duration comprised between 100 and 300 s. This exposure resulted in a significant increase of cell resistance to freeze–drying by comparison with cells cultivated in conventional bioreactors or in the TCB in the cold shock mode (CS-TCB). The mechanism behind this robustness seems to be related with the coating of microbial cells with exopolysaccharide (EPS), as assessed by the change of the zeta potential and the presence of higher EPS concentration after heat shock. Conditioning of Bifidobacteria on the basis of the heat shock technique is interesting from the practical and economical point of view since this strategy can be directly implemented in the bioreactor during stationary phase preceding cell recovery and freeze–drying.

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Keywords
Bifidobacteria; Exopolysaccharide; Bioreactors; Microbial stress; ViabilitycFDA, carboxy-fluorescein diacetate; cfu, colony forming unit; CS-TCB, cold-shock two-compartment bioreactor; DLS, dynamic light scattering; EPS, exopolysaccharide; FC, flow cytome
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Stochastic exposure to sub-lethal high temperature enhances exopolysaccharides (EPS) excretion and improves Bifidobacterium bifidum cell survival to freeze–drying
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Publisher
Database: Elsevier - ScienceDirect
Journal: Biochemical Engineering Journal - Volume 88, 15 July 2014, Pages 85–94
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