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Development of a feeding strategy for high cell and PHA density fed-batch fermentation of Ralstonia eutropha H16 from organic acids and their salts

Paper ID Volume ID Publish Year Pages File Format Full-Text
34387 45023 2015 8 PDF Available
Title
Development of a feeding strategy for high cell and PHA density fed-batch fermentation of Ralstonia eutropha H16 from organic acids and their salts
Abstract

•A fed batch fermentation strategy was designed for Ralstonia eutropha using organic acids as feedstock.•Organic acids were fed by pH-stat, and organic acid salts were fed using pO2-dependent feed control.•A fed batch strategy using three successive carbon/nitrogen ratios (10, 90, to infinite) was employed to maximize PHA productivity.•Biomass yield of 112.0 g/L, PHA yield of 93.5 g/L, and a PHA productivity of 2.13 g/L/h was achieved using the strategy outlined in this work.

The utilization of inexpensive carbon sources, including waste streams, for production of value added products has been explored for over two decades. Palm oil mill effluent (POME), a waste water stream from the palm oil industry, can be used to produce organic acids and their salts by anaerobic digestion. These organic acids are suitable as the main carbon source for growth and production of polyhydroxyalkanoates (PHAs) by organisms like Ralstonia eutropha. The presence of propionate/propionic acid results in the biosynthesis of the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(HB-co-HV)], which is desired for its favourable thermal and mechanical properties compared to the polyhydroxybutyrate (PHB) homopolymer. A specially-designed fed-batch strategy is necessary to decrease the toxic effects of organic acids in cultures of R. eutropha. A pH-stat fed-batch culture technique, using organic acids as the main carbon source, was adopted in combination with an additional pO2-dependent feed for delivering organic acid salts. The developed strategy is highly reproducible and shows a high productivity of >2 g PHA/L/h. After 44 h of fermentation, 112.4 ± 2.3 g/L cell dry weight (CDW) with 83.3 ± 1.1% P(HB-co-HV)/CDW containing 5.6 ± 0.4 mol% 3-hydroxyvalerate (3HV) were achieved. The described productivity, CDW and P(HB-co-HV)/CDW values are by far the highest reported results for R. eutropha cultivated on mixed organic acids as the main carbon source.

Keywords
Ralstonia eutropha; pH-stat culture; Mixed organic acids; Waste stream utilization; Palm oil mill effluent
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Development of a feeding strategy for high cell and PHA density fed-batch fermentation of Ralstonia eutropha H16 from organic acids and their salts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Process Biochemistry - Volume 50, Issue 2, February 2015, Pages 165–172
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