Microbial Responses to the Physicochemical Properties and Reactor’s Operational Parameters in Vinasse Digestion in a Pilot-Scale Hybrid Anaerobic Reactor

Abstract Physicochemical and operational parameters affect microbial communities, impacting anaerobic digestion (AD) systems. Microbial dynamics in response to these parameters were temporally investigated by DNA and cDNA of the 16 S rrna gene in a pilot-scale hybrid anaerobic reactor (HAnR) fed with sugarcane vinasse. Key microbes for biogas production, including Bacteroidetes -vadinHA17, Paludibacteraceae -H1, Prolixibacteraceae , Desulfovibrio , Syntrophobacter and Methanospirillum , were favored by the maintenance of volatile fatty acids (VFA) < 3700 mg.L − 1 , pH ≥ 5.6, temperature ≥ 29.8 °C, chemical oxygen demand (COD) < 31.4 g.L − 1 and organic loading rate (OLR) < 9.7 kg.COD.m − 3 .d − 1 . Temperature and pH also favored the redundancy of fermentation and H 2 -mediated methanogenesis and the evenness and diversity indexes, all related to biogas quality. Concentrations up to 2,050 mg.SO 4 2− .L − 1 , 3,270 mg.K.L − 1 , 367 mg.Mg.L − 1 , 0.4 mg.Cu.L − 1 and 1.1 mg.Zn.L − 1 led to adverse effects over microbial abundance, functional redundancy and ecology, but tolerant microorganisms, like Paludibacteraceae , Anaerolineaceae and Methanosaeta , kept fermentation and methanogenesis ongoing, although less efficiently. Microbial interactions were also affected by evaluated parameters beyond metabolic dependence. This study highlights the importance of parameter monitoring in scaled-up AD reactors to promote the adequate establishment of microbial communities and therefore contribute to system stability.