Determination of Denitrification Genes Abundance in Environmental Samples

Abstract Diversity of microorganisms involved in the biogeochemical N cycle is of fundamental interest in microbial ecology. Denitrification is a key step in the cycle by which nitrate is reduced to dinitrogen gas via the soluble nitrite and the gaseous compounds nitric oxide and nitrous oxide. The process is carried out by the sequential activity of the nitrate, nitrite, nitric oxide, and nitrous oxide reductase enzyme, respectively. The fluorescence-based quantitative real-time polymerase chain reaction (qPCR) is widely used for quantification of nucleic acids in samples obtained from numerous, diverse sources. Here, we provide a well-proven methodology for isolation of DNA from environmental samples and describe relevant experimental conditions for utilization of qPCR to assay the 16S rRNA and nar/nap, nirK/nirS, c-nor/qnor, and nos denitrification genes that encode synthesis of denitrifying enzymes. The ISO 11063 standard method and MIQUE guidelines are considered with the aim to increase experimental transparency

Impact on the microbial population during biological volatile fatty acid production from olive mill solid waste

Volatile fatty acids (VFAs) revalorisation from waste products are key in achieving industrial sustainability and circular economic goals. Hence, the objective of this work was to correlate the adaptability of the microbial community in olive mill solid waste (OMSW) anaerobic fermentation processes, to the production of VFAs under different pH conditions, i.e. under acidic (pH 4 &5), neutral (pH 6 & 7) and alkaline conditions (pH 9 & 10). At neutral conditions, anaerobic digestion exhibited minimal accumulation of VFAs, as they were primarily biotransformed to methane, where no significant changes in the microbial community were observed. At acidic conditions, a diverse profile of VFAs were present in the reactors, although the VFA production was limited to around 20 % of fed OMSW. Despite the low accumulation, the VFA profile at pH 5 was more complex than those at alkaline conditions, accounting propionic acid as the main VFA compound produced at pH 5 (60 % of the total VFAs). Acidic conditions entailed a shift in the microbial composition compared to the initial inoculum, although the reactors maintained similar diversity indices. At alkaline conditions, around 50 % of the fed OMSW was accumulated as VFAs, mainly as acetic acid. Overall, a lower diversity and higher dominance corresponded to a less diverse VFAs profile, such as the preponderance of acetic acid correlated with a microbial diversity decrease and the increased dominance of TissirellaThis work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (Ref. PID2020-116698RB-100). Dr. Antonio Serrano was funded by the Consejería de Transformaci´ on Econ´ omica, Industria, Conocimiento y Universidades (Junta de Andalucía - EMERGIA20_00114). Juan Cubero-Cardoso was funded by the Recualificaci´ on del Profesorado Universitario (Next Generation European Funds and Spanish University Ministry system). The authors also wish to express their gratitude to Nieves Escolano for her technical contribution to this researchDepartamento de Química "Profesor José Carlos Vílchez Martín

Impact on the microbial population during biological volatile fatty acid production from olive mill solid waste

12 Páginas.-- 4 Figuras.-- 3 TablasVolatile fatty acids (VFAs) revalorisation from waste products are key in achieving industrial sustainability and circular economic goals. Hence, the objective of this work was to correlate the adaptability of the microbial community in olive mill solid waste (OMSW) anaerobic fermentation processes, to the production of VFAs under different pH conditions, i.e. under acidic (pH 4 &5), neutral (pH 6 & 7) and alkaline conditions (pH 9 & 10). At neutral conditions, anaerobic digestion exhibited minimal accumulation of VFAs, as they were primarily biotransformed to methane, where no significant changes in the microbial community were observed. At acidic conditions, a diverse profile of VFAs were present in the reactors, although the VFA production was limited to around 20 % of fed OMSW. Despite the low accumulation, the VFA profile at pH 5 was more complex than those at alkaline conditions, accounting propionic acid as the main VFA compound produced at pH 5 (60 % of the total VFAs). Acidic conditions entailed a shift in the microbial composition compared to the initial inoculum, although the reactors maintained similar diversity indices. At alkaline conditions, around 50 % of the fed OMSW was accumulated as VFAs, mainly as acetic acid. Overall, a lower diversity and higher dominance corresponded to a less diverse VFAs profile, such as the preponderance of acetic acid correlated with a microbial diversity decrease and the increased dominance of Tissirella.This work was funded by the Spanish Ministry of Economy, Industry and Competitiveness (Ref. PID2020-116698RB-100). Dr. Antonio Serrano was funded by the Consejería de Transformación Económica, Industria, Conocimiento y Universidades (Junta de Andalucía - EMERGIA20_00114). Juan Cubero-Cardoso was funded by the Recualificación del Profesorado Universitario (Next Generation European Funds and Spanish University Ministry system). The authors also wish to express their gratitude to Nieves Escolano for her technical contribution to this research.Peer reviewe