Improved cultivation of Pediococcus acidilactici by in situ removal of lactic acid using polymeric resin
Lactic acid bacteria (LAB) are industrially important microorganisms recognized for fermentative ability mostly in their probiotic benefits as well as lactic acid production for various applications. Nevertheless, fermentation employing LAB often suffers end-product inhibition which reduces th...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
2017
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/75878/1/FBSB%202017%2038%20IR.pdf |
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| Summary: | Lactic acid bacteria (LAB) are industrially important microorganisms recognized for
fermentative ability mostly in their probiotic benefits as well as lactic acid
production for various applications. Nevertheless, fermentation employing LAB
often suffers end-product inhibition which reduces the cell growth rate and the
production of metabolite. The inhibition of lactic acid is due to the solubility of the
undissociated lactic acid within the cytoplasmic membrane and insolubility of
dissociated lactate, which causes acidification of cytoplasm and failure of proton
motive forces. This phenomenon influences the transmembrane pH gradient and
decreases the amount of energy available for cell growth. The utility of adsorbent
resins for in-situ lactic acid removal to enhance the cultivation performance of
Pediococcus acidilactici was studied in shake flask culture and 2 L stirred tank
bioreactor. Five different types of anion-exchange resin (namely Amberlite IRA 67,
IRA 410, IRA 400, Duolite A7 and Bowex MSA) were screened for the highest
uptake capacity of lactic acid based on Langmuir adsorption isotherm. Weak base
anion-exchange resin, Amberlite IRA 67 gave the highest maximum uptake capacity
of lactic acid (0.996 g lactic acid/g wet resin) compared to the other anion-exchange
resins. The effect of different loading concentrations (5 - 40 g/L) of anion-exchange
resin on the performance of batch cultivation of P. acidilactici was also evaluated.
High loading concentrations of anion-exchange resin showed an inhibitory effect on
the growth of P. acidilactici. The application of IRA 67 anion-exchange resin in
batch and constant fed-batch fermentation improved the growth of P. acidilactici
about 67 times and 56 times, respectively compared to the control batch fermentation
without resin addition. Nevertheless, the in situ addition of dispersed resin in the
culture created shear stress by resins collision and caused direct shear force to the
cells. The growth of P. acidilactici in the integrated bioreactor-internal column
system containing anion-exchange resin was further improved by 1.4 times over that obtained in the bioreactor containing dispersed resin. The improvement of the P.
acidilactici growth indicated that extractive fermentation using solid phase is an
effective approach for reducing by-product inhibition and increasing product titer. |
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