title: Effect of pH on ethanol-type acidogenic fermentation of fruit and vegetable waste.
abstract: The aim of this study was to investigate the possibility and optimal controlling strategy for ethanol-type acidogenic fermentation of fruit and vegetable waste by mixed microbial cultures. Four continuous stirred tank reactors (CSTR) were operated at various pHs (4.0, 5.0, 5.5, and 6.0) with an organic loading rate of 13gVS/(Ld) and hydraulic retention time of 3d. Butyrate-type fermentation was observed at pH 5.0, 5.5, and 6.0. Conversely, at pH 4.0, ethanol-type fermentation was observed with a high mass concentration and proportion (of total fermentative products) of ethanol, which were 6.7g/L and 88.8%, respectively. However, the total concentration of ethanol-type fermentative products substantially decreased from days 22-25. The optimal pH of ethanol-type fermentative microorganisms was investigated by using batch experiments with pH controlled at 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, and 7.0 and results showed that the maximum ethanol concentration and relatively highest acidogenic rate were found at pH of 5.5. The pH in the long term CSTR was changed from 4.0 to 5.5 to improve ethanol-type fermentation and results showed that ethanol-type fermentation was improved temporarily, however, was followed by the reappearance of butyrate-type fermentation. In addition, ethanol-type fermentation recovered once more when pH was reverted to 4.0. Therefore, the results of this study suggest that a process of dynamic, sequenced pH control with the order pH 4.0, 5.5 and 4.0 might be a feasible controlling strategy for continuous and stable ethanol-type fermentation.
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Haidian District, Beijing 100084, China; Research and Development Center of Beijing Capital Co. Ltd, Chaoyang District, Beijing 100028, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Wu
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Haidian District, Beijing 100084, China.
authors.forename: Cuiping
authors.initials: C
authors.lastname: Wang
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Haidian District, Beijing 100084, China.
authors.forename: Mingyue
authors.initials: M
authors.lastname: Zheng
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Haidian District, Beijing 100084, China.
authors.forename: Jiane
authors.initials: J
authors.lastname: Zuo
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Haidian District, Beijing 100084, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Haidian District, Beijing 100084, China. Electronic address: wkj@tsinghua.edu.cn.
authors.forename: Kaijun
authors.initials: K
authors.lastname: Wang
authors.affiliation: Economics and Management School, Beijing University of Agriculture, Changping District, Beijing 102206, China. Electronic address: yangboqiong@126.com.
authors.forename: Boqiong
authors.initials: B
authors.lastname: Yang
mesh_terms: D000693:Anaerobiosis; D001419:Bacteria / Q000378:metabolism*; D019149:Bioreactors; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005638:Fruit / Q000737:chemistry*; D005735:Garbage; D006863:Hydrogen-Ion Concentration; D062611:Solid Waste / Q000032:analysis*; D014675:Vegetables / Q000737:chemistry*; D018505:Waste Management / Q000379:methods*
chemical_list: D062611:Solid Waste; D000431:Ethanol
keywords: Acidogenic fermentation; Ethanol; Ethanol-type fermentation; Two-phase anaerobic digestion; pH