title: Production of high optical purity l-lactic acid from waste activated sludge by supplementing carbohydrate: effect of temperature and pretreatment time.
abstract: It has been widely accepted that the most environmentally beneficial way to treat waste activated sludge (WAS), the byproduct of municipal wastewater treatment plant, is to recover the valuable organic acid. However, the bio-conversion of lactic acid, one of the high added-value chemical, is seldom reported from WAS fermentation. In this paper, l-lactic acid was observed dominant in the WAS fermentation liquid with carbohydrate addition at ambient temperature. Furthermore, the effect of temperature on l-lactic acid and d-lactic acid production was fully discussed: two isomers were rapidly produced and consumed up in one day at mesophilic condition; and almost optically pure l-lactic acid was generated at thermophilic condition, yet time-consuming with yield of l-lactic acid enhancing by 52.9% compared to that at ambient temperature. The study mechanism showed that mesophilic condition was optimal for both production and consumption of l-lactic acid and d-lactic acid, while consumption of l-lactic acid and production of d-lactic acid were severely inhibited at thermophilic condition. Therefore, by maintaining thermophilic for 4 h in advance and subsequently fermenting mesophilic for 34 h, the concentration of l-lactic acid with optical activity of 98.3% was improved to 16.6 ± 0.5 g COD/L at a high specific efficiency of 0.6097/d.
authors.affiliation: a College of Mechanical Engineering , Shanghai University of Engineering Science , Shanghai , People's Republic of China.
authors.forename: Qiwei
authors.initials: Q
authors.lastname: Jian
authors.affiliation: b College of Environmental Science and Engineering , Donghua University , Shanghai , People's Republic of China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: c State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering , Tongji University , Shanghai , People's Republic of China.
authors.forename: Yinguang
authors.initials: Y
authors.lastname: Chen
authors.affiliation: b College of Environmental Science and Engineering , Donghua University , Shanghai , People's Republic of China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: a College of Mechanical Engineering , Shanghai University of Engineering Science , Shanghai , People's Republic of China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Pan
mesh_terms: D002241:Carbohydrates / Q000737:chemistry; D005285:Fermentation; D019344:Lactic Acid / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D002241:Carbohydrates; D012722:Sewage; D019344:Lactic Acid
keywords: Waste activated sludge; carbohydrate; fermentation; l-lactic acid; temperature