title: Water-insoluble material from apple pomace makes changes in intracellular NAD⁺/NADH ratio and pyrophosphate content and stimulates fermentative production of hydrogen.
abstract: Apple pomace is one of the major agricultural residues in Aomori prefecture, Japan, and it would be useful to develop effective applications for it. As apple pomace contains easily fermentable sugars such as glucose, fructose and sucrose, it can be used as a feedstock for the fermentation of fuels and chemicals. We previously isolated a new hydrogen-producing bacterium, Clostridium beijerinckii HU-1, which could produce H2 at a production rate of 14.5 mmol of H2/L/h in a fed-batch culture at 37 °C, pH 6.0. In this work we found that the HU-1 strain produces H2 at an approximately 20% greater rate when the fermentation medium contains the water-insoluble material from apple pomace. The water-insoluble material from apple pomace caused a metabolic shift that stimulated H2 production. HU-1 showed a decrease of lactate production, which consumes NADH, accompanied by an increase of the intracellular pyrophosphate content, which is an inhibitor of lactate dehydrogenase. The intracellular NAD(+)/NADH ratios of HU-1 during H2 fermentation were maintained in a more reductive state than those observed without the addition of the water insoluble material. To correct the abnormal intracellular redox balance, caused by the repression of lactate production, H2 production with NADH oxidation must be stimulated.
authors.affiliation: Graduate School of Agriculture and Life Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Sato
authors.affiliation: Graduate School of Agriculture and Life Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan.
authors.forename: Yuma
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Graduate School of Agriculture and Life Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Sanbongi High School of Agriculture, Towada, Aomori 034-8578, Japan.
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Sasaki
authors.affiliation: Graduate School of Agriculture and Life Science, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan. Electronic address: sonoki@cc.hirosaki-u.ac.jp.
authors.forename: Tomonori
authors.initials: T
authors.lastname: Sonoki
mesh_terms: D061249:Batch Cell Culture Techniques; D019149:Bioreactors / Q000382:microbiology; D050260:Carbohydrate Metabolism; D003013:Clostridium / Q000378:metabolism; D011756:Diphosphates / Q000378:metabolism*; D005285:Fermentation; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007564:Japan; D007770:L-Lactate Dehydrogenase / Q000037:antagonists & inhibitors; D019344:Lactic Acid / Q000096:biosynthesis; D027845:Malus / Q000737:chemistry*; D009243:NAD / Q000378:metabolism*; D010084:Oxidation-Reduction; D012995:Solubility; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D011756:Diphosphates; D014867:Water; D009243:NAD; D019344:Lactic Acid; C107241:diphosphoric acid; D006859:Hydrogen; D007770:L-Lactate Dehydrogenase
keywords: Apple pomace; Hydrogen; Lactate; NAD(+)/NADH; Pyrophosphate