Metataxonomic characterization of bacterial and archaeal community involved in hydrogen and methane production from citrus peel waste (Citrus sinensis L. Osbeck) in batch reactors

Abstract

In order to obtain enhanced value-added products, Citrus Peel Waste (CPW) was used as a lignocellulosic substrate for H2 and Volatile Fatty Acids (VFA) production (Stage I), combined with the CH4 production using these metabolites as substrate (Stage II). Stage I used 15 gCPW.L−1, 2.25 gTVS.L−1 of autochthonous inoculum, 3 gTVS.L−1 of allochthonous inoculum (UASB sludge applied to sugarcane vinasse treatment) in batch reactors operated with 40% of headspace, at 30 °C and under static conditions and pH adjusted to 8.5. These conditions allowed obtaining 13.29 mmolH2. L−1 and 1340 mg L−1 of acetic acid in Stage I. Using 125 mL of the acidified effluent (filtered liquid fraction), in Stage I, as substrate in 250 Duhran flasks, with pH adjusted to 7.0, 3 gTVS.L−1 of the same allochthonous inoculum and Zinder medium, 50.2 mmolCH4. L−1 was obtained in Stage II. The metataxonomic and metabolic potential were inferred by means of high throughput amplicon sequencing of the 16S rRNA gene on the Illumina HiSeq platform. It can be stated that the cellulolytic enzymes producers Escherichia and Clostridium were the main bacteria genera involved in CPW fermentation in Stage I, while Methanoplasma and Methanosarcina were the main archaea genera involved in CH4 production in Stage II. Besides that, it was possible to infer that Acetyl-CoA synthetase was the enzyme inferred in higher proportions in Stage II, probably due to the predominance of acetoclastic methanogenesis at this stage.