title: Bacterial production of isobutanol without expensive reagents.
abstract: Isobutanol is attracting attention as a potential biofuel because it has higher energy density and lower hygroscopicity than ethanol. To date, several effective methods for microbial production of isobutanol have been developed, but they require expensive reagents to maintain expression plasmids and induce expression, which is not suitable for practical production. Here, we describe a simple and efficient method for isobutanol production in Escherichia coli. It is noteworthy that no expression plasmids or inducers were used during the production. Instead, heterologous genes necessary for isobutanol production were all knocked into the genome, and the expression of those genes was induced by xylose, which is present in most biomass feedstocks. The constructed strain (mlcXT7-LAFC-AAKCD) contains Bacillus subtilis alsS, E. coli ilvCD, Lactococcus lactis adhA, and L. lactis kivd genes in its genome and efficiently produced isobutanol from glucose and xylose in flask batch cultures. Under conditions in which the temperature and pH of the medium and the aeration in the culture were all optimized, the final isobutanol concentration reached 8.4 g L(-1) after 48 h. Isobutanol was also produced using hydrolysate from Japanese cedar as the carbon source without supplemented glucose, xylose, or yeast extract. Under those conditions, isobutanol (3.7 g L(-1)) was produced in 96 h. Taken together, these results indicate that the developed strain is potentially useful for industrial isobutanol production.
authors.affiliation: Biomass Refinery Research Center, National Institute of Advanced Industrial Sciences and Technology (AIST), 3-11-32 Kagamiyama, Higashi-Hiroshima, Hiroshima, 739-0046, Japan.
authors.forename: Hironaga
authors.initials: H
authors.lastname: Akita
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Nakashima
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Hoshino
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D061249:Batch Cell Culture Techniques; D056804:Biofuels / Q000382:microbiology*; D000440:Butanols / Q000737:chemistry*; D002244:Carbon / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D053938:DNA Fragmentation; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D000431:Ethanol / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D013294:Lactococcus lactis / Q000235:genetics*; D013696:Temperature; D017155:Wettability; D014994:Xylose / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D056804:Biofuels; D000440:Butanols; D003470:Culture Media; D004269:DNA, Bacterial; D007202:Indicators and Reagents; D000431:Ethanol; C040507:isobutyl alcohol; D002244:Carbon; D014994:Xylose