Formate and Nitrate Utilization in Enterobacter aerogenes for Semi‐Anaerobic Production of Isobutanol

Abstract

Anaerobic bioprocessing is preferred because of its economic advantages. However, low productivity and decreased growth of the host strain have limited the use of the anaerobic process. Anaerobic respiration can be applied to anoxic processing using formate and nitrate metabolism to improve the productivity of value-added metabolites. A isobutanol-producing strains is constructed using Enterobacter aerogenes as a host strain by metabolic engineering approaches. The byproduct pathway (ldhA, budA, and pflB) is knocked out, and heterologous keto-acid decarboxylase (kivD) and alcohol dehydrogenase (adhA) are expressed along with the L-valine synthesis pathway (ilvCD and budB). The pyruvate formate-lyase mutant shows decreased growth rates when cultivated in semi-anaerobic conditions, which results in a decline in productivity. When formate and nitrate are supplied in the culture medium, the growth rates and amount of isobutanol production is restored (4.4 g L , 0.23 g g glucose, 0.18 g L h ). To determine the function of the formate and nitrate coupling reaction system, the mutant strains that could not utilize formate or nitrate is contructed. Decreased growth and productivity are observed in the nitrate reductase (narG) mutant strain. This is the first report of engineering isobutanol-producing E. aerogenes to increase strain fitness via augmentation of formate and nitrate metabolism during anaerobic cultivation.

The Glutaredoxin Gene, grxB, Affects Acid Tolerance, Surface Hydrophobicity, Auto-Aggregation, and Biofilm Formation in Cronobacter sakazakii

“…The Cronobacter genus, formerly known as Enterobacter sakazakii ( Iversen et al, 2007 ), is a group of opportunistic pathogens that cause rare but life-threatening cases of necrotizing enterocolitis, meningitis, cyst formation, intracerebral infarctions, bacteremia, and sepsis in premature neonates and infants with underlying chronic conditions ( NazarowecWhite and Farber, 1997 ; Bahloul et al, 2017 ; Jung et al, 2017 ; Sharma and Melkania, 2017 ). The International Commission on Microbiological Specification for Foods has ranked Cronobacter ( E. sakazakii ) as a “severe hazard for restricted populations, life threatening or substantial chronic sequelae of long duration” ( Yan et al, 2012 ).…”

Biorefinery: The Production of Isobutanol from Biomass Feedstocks

“…Duckweed [61,85] is a fast-growing non-food crop with few growth requirements that is very easy to handle. Empty fruit bunches [62] are a large byproduct of palm oil production and sugarcane bagasse [63] is a common industrial byproduct. Their pretreated fermentation inhibitor content is low, as can be concluded from the comparison with glucose fermentation.…”

Improved production of 2,3‐butanediol and isobutanol by engineering electron transport chain in Escherichia coli

“…We attempted to produce two reduced chemical products, 2,3-BDO and isobutanol, from engineered strains since the redundant pyruvate was accumulated and higher redox ratio was expected in the ETC mutants. The 2,3-BDO synthesis pathway was constructed by introducing budABC (from E. aerogenes) harbouring plasmid and the isobutanol production pathway by introducing plasmid harbouring ilvDC and budB (from K. pneumoniae) along with kivD and adhA (from L. lactis), to the engineered strains (Mazumdar et al, 2013;Jung et al, 2017). The 2,3-BDO and isobutanol producing transformants were termed as 'strain-BDO' and 'strain-IB' respectively ( Table 1).…”