title: Production of citric acid using its extraction wastewater treated by anaerobic digestion and ion exchange in an integrated citric acid-methane fermentation process.
abstract: In order to solve the problem of extraction wastewater pollution in citric acid industry, an integrated citric acid-methane fermentation process is proposed in this study. Extraction wastewater was treated by mesophilic anaerobic digestion and then used to make mash for the next batch of citric acid fermentation. The recycling process was done for seven batches. Citric acid production (82.4 g/L on average) decreased by 34.1 % in the recycling batches (2nd-7th) compared with the first batch. And the residual reducing sugar exceeded 40 g/L on average in the recycling batches. Pigment substances, acetic acid, ammonium, and metal ions in anaerobic digestion effluent (ADE) were considered to be the inhibitors, and their effects on the fermentation were studied. Results indicated that ammonium, Na(+) and K(+) in the ADE significantly inhibited citric acid fermentation. Therefore, the ADE was treated by acidic cation exchange resin prior to reuse to make mash for citric acid fermentation. The recycling process was performed for ten batches, and citric acid productions in the recycling batches were 126.6 g/L on average, increasing by 1.7 % compared with the first batch. This process could eliminate extraction wastewater discharge and reduce water resource consumption.
authors: The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.
authors: Jian
authors: J
authors: Xu
authors: Yang-Qiu
authors: YQ
authors: Chen
authors: Hong-Jian
authors: HJ
authors: Zhang
authors: Lei
authors: L
authors: Tang
authors: Ke
authors: K
authors: Wang
authors: Jian-Hua
authors: JH
authors: Zhang
authors: Xu-Sheng
authors: XS
authors: Chen
authors: Zhong-Gui
authors: ZG
authors: Mao
mesh_terms: D000693:Anaerobiosis; D001234:Aspergillus niger / Q000254:growth & development*; D019343:Citric Acid / Q000378:metabolism*; D008697:Methane / Q000378:metabolism*; D062065:Wastewater / Q000737:chemistry*; D018508:Water Purification
chemical_list: D019343:Citric Acid; D008697:Methane; D062065:Wastewater