Succinic acid-producing biofilms of Actinobacillus succinogenes: reproducibility, stability and productivity

Abstract

Continuous anaerobic fermentations were performed in a biofilm reactor packed with Poraver® beads. Dilution rates (D) varied between 0.054 h -1 and 0.72 h -1 and D-glucose and CO 2 gas were used as carbon substrates. Steady-state conditions were shown to be repeatable and independent of the operational history. Production stability was achieved over periods exceeding 80 h at values of D below 0.32 h -1 . In these situations, steady-state variation (expressed as fluctuations in NaOH neutralisation flow rates) exhibited a standard deviation of less than 5% while no indication of biofilm deactivation was detected. The total biomass amount was found to be independent of the dilution rate with an average dry concentration of

The pentose phosphate pathway leads to enhanced succinic acid flux in biofilms of wild-type Actinobacillus succinogenes

“…Similar to previous continuous, biofilm studies on A. succinogenes Bradfield and Nicol, 2016;Brink and Nicol, 2014;Maharaj et al, 2014), in the current study, the succinic acid yield on substrate ( Figure 2A) and the ratio of succinic acid to acetic acid (Y AASA ; Figure 2B) increased with increasing succinic acid titre (C SA ). Furthermore, the formic acid-to-acetic acid ratio (Y AAFA ) decreased with increasing C SA ( Figure 2B), indicating increased pyruvate-or formate dehydrogenase activity It has been suggested that these trends are linked to a titre-dependent shift in metabolism from a growth to a non-growth or stationary mode Brink and Nicol, 2014), with associated incomplete closures of mass and redox balances.…”

“…As a result, less biofilm was present in the fermenter compared to previous fermentations using a similar fermentation setup Bradfield and Nicol, 2016;Maharaj et al, 2014).…”

“…competitive performance on both a variety of monosaccharides Liu et al, 2008;Maharaj et al, 2014;Yan et al, 2014) and scalable biorefinery streams (Bradfield et al, 2015;Salvachúa et al, 2016), and is able to tolerate high acid titres (Lin et al, 2008) while necessarily fixing CO 2 during succinate production (Guettler et al, 1999).…”

Continuous succinic acid production from xylose by Actinobacillus succinogenes

“…succinogenes [11,12]. However, the dehydrogenase activity appears to be lower in the case of xylose since YAAFA does not decrease to the same extent as in the glucose study.…”

“…Various microbial platforms have been explored for bio-production of SA with the best bench-scale performance achieved by Actinobacillus succinogenes [11][12][13][14], Anaerobiospirillum succiniciproducens [15,16], Mannheimia succiniciproducens [17][18][19], and engineered strains of Escherichia coli [20][21][22].…”