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Communication Dans Un Congrès Année : 2022

Pretreatment for dark fermentation : impact on indigenous bacteria

Résumé

Few recent studies have shown that fermentation for biohydrogen production can be effectively performed without any inoculation, using indigenous bacteria. In parallel, some pretreatments can be applied either to the inoculum to select some hydrogen-producing microorganisms and remove methanogens, or to the solid substrates to increase the concentration of soluble sugars and increase the biohydrogen yield. Pretreatments commonly applied to the inoculum are thermal treatments whereas pretreatments used to solubilize sugars include acid pretreatment and sonication. The objective of this study was to investigate, at the same time, the impact of thermal, acid and sonication pretreatments on both waste indigenous bacteria and on waste solubilisation in order to increase the biohydrogen potential. Firstly, Biochemical Hydrogen Potential (BHP) tests were carried out in 4 different conditions for 7 substrates (dates, corn silage, sorghum, microalgae, sewage sludge, organic fraction of municipal solid waste (OFMSW) and food waste): 1) with untreated-substrate without inoculum, 2) thermal pretreated (90°C for 15 min) substrate without inoculum, 3) with inoculum and without pretreatment, and 4) substrate and inoculum were thermally pretreated simultaneously. Secondly, thermal-acid (90°C-30 min, 10% TS with [HCl ]= 11.0 mmol/gVSini or [H2SO4 ]= 22.8 mmol/gVSini) and ultrasound (59.4 kJ/gTS) pretreatments were carried on OFMSW. BHP were carried out with raw and pretreated waste and with inoculum. In addition, some tests were run with irradiated OFMSW (45 kGy, to remove endogenous bacteria) and others without inoculum. Except for protein-rich substrates (sewage sludge and microalgae),: similar hydrogen yields, total metabolite productions and metabolic pathways were for achieved for indigenous bacteria (both thermally pretreated and nonpretreated) and pretreated exogenous bacteria. According the substrates, bacterial compositions at the end of fermentation, showed different patterns after thermal treatment in comparison to untreated ones. They were similar for corn silage, sorghum, OFMSW and non-inoculated food waste. Clostridiales orders proportion increased for dates, algae, sludge and inoculated food waste. Thermal-acid pretreatments are particularly efficient to improve sugar solubilization. Sonication and acid pretreatments were inefficient to improve H2 yield. Nevertheless, they induced metabolic changes from acetate toward butyrate or ethanol. Pretreatments led to a decrease in Enterobacter cloacae and an enrichment in Clostridium sp. After indigenous bacteria inactivated by gamma irradiation, metabolic and bacterial composition did not change.
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Dates et versions

hal-04124358 , version 1 (09-06-2023)

Identifiants

  • HAL Id : hal-04124358 , version 1

Citer

K Dauptain, E Trably, H Carrere. Pretreatment for dark fermentation : impact on indigenous bacteria. 42nd Frontier Scientists Workshop, Environmental Bio-Technology workshop for reducing GHGs emissions, Nov 2022, Narbonne, France. ⟨hal-04124358⟩

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