Temperature is crucial for the performance of anaerobic digestion process. In this study of anaerobic digestion of swine manure, the relationship between the microbial gene expression and methane production at different temperatures (25-55 degrees C) was revealed through metatranscriptomic analysis. Daily methane production and total biogas production increased with temperature up to 50 degrees C, but decreased at 55 degrees C. The functional gene expression showed great variation at different temperatures. The function centralization (opposite to alpha-diversity), assessed by the least proportions of functional pathways contributing for at least 50% of total reads positively correlated to methane production. Temperature regulated methane production probably through reducing the diversity of functional pathways, but enhancing central functional pathways, so that most of cellular activities and resource were invested in methanogenesis and related pathways, enhancing the efficiency of conversion of substrates to methane. This research demonstrated the importance of function centralization for efficient system functioning. (C) 2016 Elsevier Ltd. All rights reserved.