Open AccessCo‐inoculating ruminal content neither provides active hydrolytic microbes nor improves methanization of 13 C ‐cellulose in batch digesters
Author(s) -
Chapleur Olivier,
Bize Ariane,
Serain Thibaut,
Mazéas Laurent,
Bouchez Théodore
Publication year - 2014
Publication title -
fems microbiology ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.377
H-Index - 155
eISSN - 1574-6941
pISSN - 0168-6496
DOI - 10.1111/1574-6941.12249
Subject(s) - cellulose , biology , rumen , microbial consortium , microorganism , propionate , food science , bioreactor , anaerobic digestion , biodegradation , bacteria , microbiology and biotechnology , biochemistry , botany , fermentation , ecology , genetics , methane
Cellulose hydrolysis often limits the kinetics and efficiency of anaerobic degradation in industrial digesters. In animal digestive systems, specialized microorganisms enable cellulose biodegradation at significantly higher rates. This study aims to assess the potential of ruminal microbial communities to settle and to express their cellulolytic properties in anaerobic digesters. Cellulose‐degrading batch incubations were co‐inoculated with municipal solid waste digester sludge and ruminal content. 13 C ‐labeled cellulose degradation was described over time with G as C hromatography– C ombustion– I sotope R atio M ass S pectrometry. Results were linked to the identification of the microorganisms assimilating 13 C and to the monitoring of their relative dynamics. Cellulose degradation in co‐inoculated incubations was efficient but not significantly improved. Transient disturbances in degradation pathways occurred, as revealed by propionate accumulation. A utomated R ibosomal I ntergenic S pacer A nalysis dynamics and pyrosequencing revealed that expected classes of B acteria and A rchaea were active and degraded cellulose. However, despite the favorable co‐inoculation conditions, molecular tools also revealed that no ruminal species settled in the bioreactors. Other specific parameters were probably needed for this to happen. This study shows that exploiting the rumen's cellulolytic properties in anaerobic digesters is not straightforward. Co‐inoculation can only be successful if ruminal microorganisms manage to thrive in the anaerobic digester and outcompete native microorganisms, which requires specific nutritional and environmental parameters, and a meticulous reproduction of the selection pressure encountered in the rumen.