Anaerobic digestion of sludge by different pretreatments: Changes of amino acids and microbial community

Keke Xiao, Zecong Yu, Kangyue Pei, Mei Sun, Yuwei Zhu, Sha Liang, Huijie Hou, Bingchuan Liu, Jingping Hu, Jiakuan Yang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Many studies have investigated the effects of different pretreatments on the performance of anaerobic digestion of sludge. However, the detailed changes of dissolved organic nitrogen, particularly the release behavior of proteins and the byproducts of protein hydrolysis-amino acids, are rarely known during anaerobic digestion of sludge by different pretreatments. Here we quantified the changes of three types of proteins and 17 types of amino acids in sludge samples solubilized by ultrasonic, thermal, and acid/alkaline pretreatments and their transformation during anaerobic digestion of sludge. Tryptophan protein, aromatic protein I, aromatic protein II, and cysteine were identified as the key dissolved organic nitrogen responsible for methane production during anaerobic digestion of sludge, regardless of the different pretreatment methods. Different from the depletion of other amino acids, cysteine was resistant to degradation after an incubation period of 30 days in all sludge samples. Meanwhile, the “cysteine and methionine metabolism (K00270)” was absent in all sludge samples by identifying 6755 Kyoto Encyclopedia of Genes and Genomes assignments of genes hits. Cysteine contributed to the generation of methane and the degradation of acetic, propionic, and n-butyric acids through decreasing oxidation-reduction potential and enhancing biomass activity. This study provided an alternative strategy to enhance anaerobic digestion of sludge through in situ production of cysteine. [Figure not available: see fulltext.]

Original languageEnglish
Article number23
JournalFrontiers of Environmental Science and Engineering
Issue number2
StatePublished - Feb 2022
Externally publishedYes


  • Amino acids
  • Dissolved organic nitrogen
  • Metagenomic sequencing analysis
  • Proteins
  • Sludge pretreatments
  • Structural equation model


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