Energy Conservation and Carbon Flux Distribution During Fermentation of CO or H2/CO2 by Clostridium ljungdahlii

Abstract

Tang W-Z and Li F-L (2020) Energy Conservation and Carbon Flux Distribution During Fermentation of CO or H 2 /CO 2 by Clostridium ljungdahlii.

Identifying and Engineering Bottlenecks of Autotrophic Isobutanol Formation in Recombinant C. ljungdahlii by Systemic Analysis

“…Further strain optimization may aim to detour said reductive power into isobutanol formation. In case of ethanol this goal is very challenging as ethanol may be considered as a vital by-product of the acetaldehyde:ferredoxin oxidoreductase (AOR) which links its formation with ATP synthesis ( Mock et al, 2015 ; Liew et al, 2017 ; Hermann et al, 2020 ; Liu et al, 2020 ; Zhu et al, 2020 ). However, elimination of 2,3-butanediol production may increase isobutanol formation as both products originate from the precursor pyruvate requiring NADPH as electron donor.…”

Towards continuous industrial bioprocessing with solventogenic and acetogenic clostridia: challenges, progress and perspectives

“…When referring to batch mode during gas fermentations, the liquid volume remains unchanged, while the gaseous substrate is typically supplied either at the beginning (batch mode) or as continuous flow (fed-batch) [ 98 , 276 , 340 ]. While bioreactors offer control and monitoring possibilities [ 140 ], serum bottles represent the only “real” batch cultivations in gas fermentation, delimiting gas exchange and stripping of (intermediate) products.…”

“…Nevertheless, the downtime in a fed-batch is comparable to a batch process and likewise there is no continuous substrate conversion and product formation. Multiple studies have investigated the use of fed-batch in comparison to continuous processes [ 124 , 174 , 182 , 239 , 288 , 340 ]. Li et al [ 165 ] tested batch, fed-batch and continuous process modes for ABE fermentation and recommended continuous fermentations to obtain bioprocesses with superior productivities.…”

“…Ethanol is a desired product and formed acetate leaving the process is considered a “carbon loss” [ 301 ]. Several omics studies hence investigated the influence of the pH-value and substrate limitation [ 249 ] or the composition of the feed gas [ 106 , 299 , 300 , 340 ] on ethanol formation. One interesting finding of proteome studies is that an increase in ethanol production seems not to be linked to key enzyme abundance in both C. ljungdahlii [ 249 ] and C. autoethanogenum [ 299 ], suggesting that regulation might be thermodynamically or on a posttranslational level rather than on a transcriptional level.…”

Synthetic Biology on Acetogenic Bacteria for Highly Efficient Conversion of C1 Gases to Biochemicals

“…GEMs contain the entire set of known biochemical reactions taking place in an organism and allow us to predict, in silico, the flux distribution across the metabolic pathway. Based on in silico simulation/analysis using GEMs, the carbon flux or energy balance of acetogens during C1 fixation could be better understood [ 37 , 89 , 91 , 113 , 114 , 115 , 116 , 117 ]. This large amount of information based on systems biology can help understand the genetic regulation system for the C1 fixation process of acetogens.…”