title: Enhanced production of lactic acid with reducing excess sludge by lactate fermentation.
abstract: The development of a facile technology for utilizing effectively and/or reducing excess sludge is one of the urgent problems since a large quantity of sewage sludge is formed by activated sludge processes. Excess sludge containing 50mM sucrose was fermented at 50 degrees C using endogenous bacteria in excess sludge, resulting in a high lactic acid production (8.45 g/L) and in an increased sludge reduction (38.2%). Conversion rate to lactic acid was up to 106.0% by standard fermentation at 50 degrees C compared to 43.8% at 30 degrees C and this phenomenon that conversion rate was higher was observed only at 50 degrees C as the fermentation at less or more than 50 degrees C had lower conversion rate than that at 50 degrees C. Lactic acid bacteria increased at 50 degrees C during 1-d fermentation whereas the number of total viable bacteria only increased slightly, indicating that lactic acid bacteria in sludge at 50 degrees C were preferentially able to utilize the sucrose for producing lactic acid. Finally, pH-vibration fermentation at 50 degrees C enabled to completely consume residual sucrose in the normal fermentation, resulting in the maximum production of lactic acid. Lactate fermentation by a purely cultured lactic acid bacterium TS1 with autoclaved excess sludge containing 50mM sucrose had more than 100% of conversion rate to lactic acid, indicating that a part of sludge was converted into lactic acid during the fermentation. Our technique is useful as a facile engineering for reducing excess sludge concomitantly with producing lactic acid by lactate fermentation.
authors.affiliation: Department of Biological Functions and Engineering, Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, Kitakyushu, Japan.
authors.forename: Toshinari
authors.initials: T
authors.lastname: Maeda
authors.forename: Takayuki
authors.initials: T
authors.lastname: Yoshimura
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Shimazu
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Shirai
authors.forename: Hiroaki I
authors.initials: HI
authors.lastname: Ogawa
mesh_terms: D015169:Colony Count, Microbial; D005285:Fermentation; D019344:Lactic Acid / Q000096:biosynthesis* / Q000378:metabolism; D012722:Sewage
chemical_list: D012722:Sewage; D019344:Lactic Acid