Bacterial dispersal enhances the elimination of active fecal coliforms during vermicomposting of fruit and vegetable wastes: The overlooked role of earthworm mucus

Zihao Duan; Kui Huang; Wenqi Huang; Bangchi Wang; Jiwei Shi; Hui Xia; Fusheng Li

doi:10.1016/j.jhazmat.2024.134280

Bacterial dispersal enhances the elimination of active fecal coliforms during vermicomposting of fruit and vegetable wastes: The overlooked role of earthworm mucus

J Hazard Mater. 2024 Apr 15:471:134280. doi: 10.1016/j.jhazmat.2024.134280. Online ahead of print.

Authors

Zihao Duan¹, Kui Huang², Wenqi Huang¹, Bangchi Wang¹, Jiwei Shi¹, Hui Xia³, Fusheng Li⁴

Affiliations

¹ School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China.
² School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China; River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. Electronic address: huangkui@mail.lzjtu.cn.
³ School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China; River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
⁴ River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.

PMID: 38636233
DOI: 10.1016/j.jhazmat.2024.134280

Abstract

Earthworms play a pivotal role in the elimination of fecal coliforms during vermicomposting of fruit and vegetable waste (FVWs). However, the specific mechanisms underlying the action of earthworm mucus remain unclear. This study investigated the mechanisms of fecal coliform reduction related to earthworm mucus during FVWs vermicomposting by comparing treatments with and without earthworms. The results show that the secretion of earthworm mucus decreased by 13.93 % during the startup phase, but significantly (P < 0.001) increased by 57.80 % during the degradation phase. Compared to the control without earthworms, vermicomposting led to a significant (P < 0.05) 1.22 -fold increase in the population of active bacteria, with a strong positive correlation between mucus characteristics and dominant bacterial phyla. As the dominant fecal coliforms, Escherichia coli and Klebsiella pneumoniae significantly (P < 0.05) declined by 86.20 % and 93.38 %, respectively, in the vermi-reactor relative to the control. Bacterial dispersal limitation served as a key factor constraining the elimination of E. coli (r = 0.73, P < 0.01) and K. pneumoniae (r = 0.77, P < 0.001) during vermicomposting. This study suggests that earthworm mucus increases the active bacterial abundance and cooperation by weakening the bacterial dispersal limitation, thus intensifying competition and antagonism between fecal coliforms and other bacteria.

Keywords: Active microorganisms; Dispersal limitation; Escherichia coli; Organic waste; Vermicompost.