Metagenomic analysis of an industrial-scale biogas plant fed with contaminated maize silage

Abstract

Biogas production represents one of the most economically attractive alternative technology for biofuel production from renewable resources. Generally, biogas plants are fed with agricultural residual products and food wastes, but the rising up of agricultural products contaminated by mycotoxins, such as maize silage not suitable for animal feeding, has pointed the question on the possibility to use this agricultural productfor biogas production. In this regards, a preliminary metagenomic analysis of microbial community residing in a mesophilic industrial-scale biogas fermenter, daily fed with contaminated maize silage, has been carried out to characterize the evolution of microbial community under the operating conditions and the mycotoxin content. Sample were collected from a biogas plant consisting of a three steps production taking place in a bioreactor, post-reactor and a storage tank. Total DNA was extracted from samples belonging to each steps of biogas production. Metagenomic analysis was carried out by analyzing the V4 variable region of bacterial and archaeal 16S rRNA gene. Mycotoxin content was analyzed in maize silage feeding the biogas plant and in the digestate from bioreactor, post-reactor and storage tank by immunoaffinity column clean-up (Myco6in1+®) and detected with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Over 3million high quality reads (about 1Gb) were generated on the Ion Torrent S5 Sequencing System. About 2.4 million reads were assigned for 16S analysis. In detail, metagenomic analysis revealed that Bacteria superkingdom was dominant (~96%) along the production steps, whereas Archaea were less represented (~4%). Within Bacteria the most abundant phylum was Firmicutes, mostly represented by Clostridia, followed by Bacteroidetes and Synergistetes. Within the superkingdom of Archaea, only microorganisms belonging to the phylum of Euryarchaeota were detected. Within Euryarchaeota the dominant genera were Methanosarcina and Methanoculleus. Chemical analysis on maize silage feeding the plants showed an initial mycotoxin contamination by DON (410 µg/kg), FB1 (3570 µg/kg), FB2 (810 µg/kg) and T-2 toxin (20 µg/kg), while AfB1, HT-2 Toxin, NIV, OTA and ZEA were not detected. After the first step of biogas production, a complete reduction of DON and T-2 content was achieved. These preliminary results suggest a possible absorption/degradation of mycotoxins in bioreactor tank and therefore further studies are needed to better elucidate the possible involvement of specific microbial taxa capable of mycotoxins reduction and the enzymatic pathways potentially involved in mycotoxin degradation.


Tutti gli autori

  • M. Ferrara; V. C. Liuzzi; F. Fanelli; M. Haidukowski; M. T. Cimmarusti; E. Casaletta; A. F. Logrieco; D. H. Huson; G. Mulè

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Anno di pubblicazione

2017

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