Fluorescence characteristics of dissolved organic matter during anaerobic digestion of oil crop straw inoculated with rumen liquid

• Published in: RSC advances Vol. 11; no. 24; pp. 14347 - 14356
• Main Authors: Su, Lianghu, Chen, Mei, Wang, Saier, Ji, Rongting, Liu, Chenwei, Lu, Xueqin, Zhen, Guangyin, Zhang, Longjiang
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 16.04.2021; The Royal Society of Chemistry
• Subjects: Anaerobic digestion; Biodegradation; Chemistry; Correlation analysis; Dissolved organic matter; Factor analysis; Fluorescence; Humidification; Microorganisms; Spectrum analysis; Straw; Tryptophan; Tyrosine
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d1ra01176f

Fluorescence excitation-emission matrix (EEM) spectroscopy is a powerful tool for characterizing dissolved organic matter (DOM), a key component of anaerobic digestion. In this study, the fluorescence characteristics of DOM during 55 days of anaerobic digestion of oil crop straw inoculated with rumen liquid were investigated. EEM spectroscopy coupled with parallel factor analysis (PARAFAC) showed that three major fluorescence components, tyrosine- (C 1 ), humic- (C 2 ) and tryptophan-like substances (C 3 ), were identified in all DOM samples. The F max values of C 1 and C 3 increased rapidly during the first 5 d, decreased dramatically from day 5 to day 35, and then remained stable, while C 2 was not biodegraded. The changes in the F max values of the fluorescence components reflected the biodegradation of lignin and/or embedded cellulose by rumen microorganisms. The changes in the Stokes shift of the fluorescence peak were readily explained by the variation in the hydrophobic/hydrophilic fraction distribution. The humidification index (HIX) and A : T ratio of the DOM decreased after 5 d and then increased gradually. Compared with the McKnight fluorescence index (MFI), the Y fluorescence index (YFI) was better able to track the evolution of the DOM. Correlation analysis of the different fluorescence indices (intensities) and absorbance indices was also carried out. The EEM-PARAFAC individual components, HIX and A : T ratio were conveniently used to characterize the degree of anaerobic conversion of the organic matter, and the peak at the Stokes shift of ∼1.0 μm −1 was used as one of the indicators showing the stabilization of anaerobic digestion. These findings may assist in developing fluorescence technology for monitoring the anaerobic digestion of crop straw. Characterizing DOM during the anaerobic digestion process of crop straw by EEM-PARAFAC, fluorescence indices and Stokes shift.