title: Long-term effect of the antibiotic cefalexin on methane production during waste activated sludge anaerobic digestion.
abstract: Long-term experiments herein were conducted to investigate the effect of cefalexin (CLX) on methane production during waste activated sludge (WAS) anaerobic digestion. CLX exhibited a considerable inhibition in methane production during the initial 25 days while the negative effect attenuated subsequently and methane production recovered depending on CLX doses used (600 and 1000 mg/L). The highest methane yield reached 450 mL at 1000 mg-CLX/L after 157 days of digestion, 63.8% higher than CLX-free one. Stimulated excretion of extracellular polymeric substances (EPS) by CLX served as microbial protecting layers, creating a suitable environment for microbes' growth and fermentation. Further examination via ultraviolet visible (UV-Vis) spectra also verified the elevated slime EPS, LB-EPS and TB-EPS indicated by UV-254 in the presence of CLX. Unlike the commonly accepted adverse effect, this study demonstrated the beneficial role of CLX in methane production, providing new insights into its true environmental impacts.
authors.affiliation: Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan. Electronic address: luxq@epl1.civil.tohoku.ac.jp.
authors.forename: Xueqin
authors.initials: X
authors.lastname: Lu
authors.affiliation: Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan; National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-0053, Japan. Electronic address: zhenguangyin@163.com.
authors.forename: Guangyin
authors.initials: G
authors.lastname: Zhen
authors.affiliation: Graduate School of Environmental Studies, Tohoku University, Sendai, Miyagi 980-8579, Japan.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan.
authors.forename: Toshimasa
authors.initials: T
authors.lastname: Hojo
authors.affiliation: Graduate School of Environmental Studies, Tohoku University, Sendai, Miyagi 980-8579, Japan.
authors.forename: Adriana Ledezma
authors.initials: AL
authors.lastname: Estrada
authors.affiliation: Department of Civil and Environmental Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi 980-8579, Japan; Graduate School of Environmental Studies, Tohoku University, Sendai, Miyagi 980-8579, Japan. Electronic address: yyli@epl1.civil.tohoku.ac.jp.
authors.forename: Yu-You
authors.initials: YY
authors.lastname: Li
mesh_terms: D000693:Anaerobiosis / Q000187:drug effects; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001704:Biopolymers / Q000032:analysis; D019149:Bioreactors / Q000382:microbiology; D002506:Cephalexin / Q000494:pharmacology*; D005110:Extracellular Space / Q000737:chemistry; D005232:Fatty Acids, Volatile / Q000096:biosynthesis; D008697:Methane / Q000096:biosynthesis*; D012037:Refuse Disposal / Q000379:methods*; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors; D014835:Volatilization
chemical_list: D000900:Anti-Bacterial Agents; D001704:Biopolymers; D005232:Fatty Acids, Volatile; D012722:Sewage; D002506:Cephalexin; D008697:Methane
keywords: Cefalexin; Extracellular polymeric substances (EPS); Methane production; Ultraviolet visible (UV–Vis) spectra