title: Adenine Addition Restores Cell Viability and Butanol Production in Clostridium saccharoperbutylacetonicum N1-4 (ATCC 13564) Cultivated at 37°C.
abstract: We have developed butanol-producing consolidated bioprocessing from cellulosic substrates through coculture of cellulolytic clostridia and butanol-producingClostridium saccharoperbutylacetonicumstrain N1-4. However, the butanol fermentation by strain N1-4 (which has an optimal growth temperature of 30°C) is sensitive to the higher cultivation temperature of 37°C; the nature of this deleterious effect remains unclear. Comparison of the intracellular metabolites of strain N1-4 cultivated at 30°C and 37°C revealed decreased levels of multiple primary metabolites (notably including nucleic acids and cofactors) during growth at the higher temperature. Supplementation of the culture medium with 250 mg/liter adenine enhanced both cell growth (with the optical density at 600 nm increasing from 4.3 to 10.2) and butanol production (increasing from 3.9 g/liter to 9.6 g/liter) at 37°C, compared to those obtained without adenine supplementation, such that the supplemented 37°C culture exhibited growth and butanol production approaching those observed at 30°C in the absence of adenine supplementation. These improved properties were based on the maintenance of cell viability. We further showed that adenine supplementation enhanced cell viability during growth at 37°C by maintaining ATP levels and inhibiting spore formation. This work represents the first demonstration (to our knowledge) of the importance of adenine-related metabolism for clostridial butanol production, suggesting a new means of enhancing target pathways based on metabolite levels.IMPORTANCEMetabolomic analysis revealed decreased levels of multiple primary metabolites during growth at 37°C, compared to 30°C, inC. saccharoperbutylacetonicumstrain N1-4. We found that adenine supplementation restored the cell growth and butanol production of strain N1-4 at 37°C. The effects of adenine supplementation reflected the maintenance of cell viability originating from the maintenance of ATP levels and the inhibition of spore formation. Thus, our metabolomic analysis identified the depleted metabolites that were required to maintain cell viability. Our strategy, which is expected to be applicable to a wide range of organisms, permits the identification of the limiting metabolic pathway, which can serve as a new target for molecular breeding. The other novel finding of this work is that adenine supplementation inhibits clostridial spore formation. The mechanism linking spore formation and metabolomic status in butanol-producing clostridia is expected to be the focus of further research.
authors.affiliation: Department of Fermentation Science and Technology, Faculty of Applied Bio-science, Tokyo University of Agriculture, Tokyo, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Kiyoshi
authors.affiliation: Department of Fermentation Science and Technology, Faculty of Applied Bio-science, Tokyo University of Agriculture, Tokyo, Japan.
authors.forename: Sohei
authors.initials: S
authors.lastname: Kawashima
authors.affiliation: Department of Fermentation Science and Technology, Faculty of Applied Bio-science, Tokyo University of Agriculture, Tokyo, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Nobuki
authors.affiliation: Department of Fermentation Science and Technology, Faculty of Applied Bio-science, Tokyo University of Agriculture, Tokyo, Japan.
authors.forename: Toshimori
authors.initials: T
authors.lastname: Kadokura
authors.affiliation: Department of Fermentation Science and Technology, Faculty of Applied Bio-science, Tokyo University of Agriculture, Tokyo, Japan.
authors.forename: Atsumi
authors.initials: A
authors.lastname: Nakazato
authors.affiliation: Department of Fermentation Science and Technology, Faculty of Applied Bio-science, Tokyo University of Agriculture, Tokyo, Japan.
authors.forename: Ken-Ichiro
authors.initials: KI
authors.lastname: Suzuki
authors.affiliation: Department of Fermentation Science and Technology, Faculty of Applied Bio-science, Tokyo University of Agriculture, Tokyo, Japan s3nakaya@nodai.ac.jp.
authors.forename: Shunichi
authors.initials: S
authors.lastname: Nakayama
mesh_terms: D020001:1-Butanol / Q000378:metabolism; D000096:Acetone / Q000378:metabolism; D000225:Adenine / Q000494:pharmacology*; D000255:Adenosine Triphosphate; D000440:Butanols / Q000378:metabolism*; D003013:Clostridium / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D055432:Metabolomics; D050296:Microbial Viability / Q000187:drug effects*; D013171:Spores, Bacterial / Q000187:drug effects; D013696:Temperature
chemical_list: D000440:Butanols; D003470:Culture Media; D000096:Acetone; D000431:Ethanol; D000255:Adenosine Triphosphate; D020001:1-Butanol; D005947:Glucose; D000225:Adenine
keywords: Clostridium; butanol production; metabolomic analysis; spore formation