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Flux balance analysis of mixed microbial cultures: Application to the production of polyhydroxyalkanoates from complex mixtures of volatile fatty acids

Paper ID Volume ID Publish Year Pages File Format Full-Text
23637 43459 2012 10 PDF Available
Title
Flux balance analysis of mixed microbial cultures: Application to the production of polyhydroxyalkanoates from complex mixtures of volatile fatty acids
Abstract

Fermented agro-industrial wastes are potential low cost substrates for polyhydroxyalkanoates (PHA) production by mixed microbial cultures (MMC). The use of complex substrates has however profound implications in the PHA metabolism. In this paper we investigate PHA accumulation using a lumped metabolic model that describes PHA storage from arbitrary mixtures of volatile fatty acids (VFA). Experiments were conducted using synthetic and complex VFA mixtures obtained from the fermentation of sugar cane molasses. Metabolic flux analysis (MFA) and flux balance analysis (FBA) were performed at different stages of culture enrichment in order to investigate the effect of VFA composition and time of enrichment in PHA storage efficiency. Substrate uptake and PHA storage fluxes increased over enrichment time by 70% and 73%, respectively. MFA calculations show that higher PHA storage fluxes are associated to an increase in the uptake of VFA with even number of carbon atoms and a more effective synthesis of hydroxyvalerate (HV) precursors from VFA with odd number of carbons. Furthermore, FBA shows that the key metabolic objective of a MMC subjected to the feast and famine regimen is the minimization of the tricarboxylic acid cycle fluxes. The PHA flux and biopolymer composition (hydroxybutyrate (HB): HV) could be accurately predicted in several independent experiments.

► We propose a metabolic model for multiple VFA conversion to PHA. ► This is the first model attempting to describe PHA accumulation from more than 2 VFAs. ► PHA storage fluxes and HB:HV composition were accurately predicted by flux balance analysis for several independent experiments. ► The identified metabolic objective was the minimization of TCA activity. ► NADH2 accumulation dynamics was confirmed as a key factor for the regulation of PHA accumulation from complex VFA mixtures by MFA.

Keywords
Metabolic modelling; Mixed microbial cultures; Polyhydroxyalkanoates; Volatile fatty acids; Fermented feedstockA, matrix of metabolic fluxes; Ab, matrix of known fluxes; Ac, acetate; An#, pseudo inverse matrix of unknown fluxes; An, matrix of unknown flux
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Biotechnology - Volume 162, Issues 2–3, 31 December 2012, Pages 336–345
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