Effect of high concentration of ammonium on production of n-caproate: Recovery of a high-value biochemical from food waste via lactate-driven chain elongation. (1st June 2021)

• Record Type: Journal Article
• Authors: Wei, Yong; Ren, Bing; Zheng, Shaorui; Feng, Xin; He, Yong; Zhu, Xiaoyu; Zhou, Lixiang; Li, Dong
• Is Part Of: Waste management. Volume 128(2021)
• Page Start: 25
• Page End: 35
• Publication Date: 2021-06-01
• Subjects: Ammonium -- n-caproate -- Lactate -- Chain elongation -- Food waste; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2021.04.015
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: Highlights: Chain elongation was inhibited when ammonium concentration reached 2.0 g L −1 . High levels of ammonium led to propionate accumulation. Ammonium inhibited Clostridium IV, providing opportunity to Propionibacterium . n -Caproate was recovered from undiluted food waste (FW) for the first time. Abstract: Ammonium accumulation is inevitable during the fermentation of food waste (FW), challenging the application of chain elongation process upgrading FW into the high-value biochemical n -caproate, which is a medium chain carboxylate. This study is the first to investigate ammonium inhibition of lactate-driven chain elongation process. The short-term exposure of a Clostridium IV-dominated chain elongating reactor microbiome at an ammonium concentration of 1–4 g L −1 linearly decreased n -caproate production by 25–80%. High levels of ammonium ( ≥ 5 g L −1 ) could cause failure of chain elongation, shifting the product from n -caproate to propionate. The involved mechanisms revealed that ammonium reshaped the microbial community from Clostridium IV domination to Clostridium IV and Propionibacterium co-domination (based on 16S rRNA sequencing) and reduced the activities of key enzymes involved in the reversed β-oxidization pathway. We propose an effective strategy from our study, which is the first one to do in our knowledge, to upgrade raw FW without dilution to n -caproate: lowering the ammonium accumulation to 1.0 g L −1 at the setup phase for adaptation and prolonging the hydraulic retention time (10 days) during the operation phase for the colonization of chain-elongation bacteria. These findings lay a foundation for the implementation of the LCE process on FW, providing an alternative way to alleviate the global FW crisis.