Improving the non-sterile food waste bioconversion to hydrogen by microwave pretreatment and bioaugmentation with Clostridium butyricum

Hydrogen production from acidogenic food waste fermentation using untreated inoculum: Effect of substrate concentrations

“…The rate sharply decreased to 4.2% when the substrate concentration increased to 22.5 g-VS/L and remained below 5% in reactors with more FW, which further explains the lower H 2 yield in these reactors, and might be owing to the restriction by the rapid acidification and lower pH during the fermentation process. Given the existence of indigenous microorganisms such as LAB and acetogens in the fresh FW, most of the substrates were transformed into organic acids and led to a decrease in pH, which in turn restricted the substrate degradation [5]. Additionally, in the reactors with 15 g-VS/L, the COD removal rate using fresh FW was very close to that using heat-treated FW as feedstock, but a much lower amount of hydrogen was observed.…”

“…It was found that large amounts of microorganisms exist in fresh FW [3], and different types of microorganisms in the system can synergistically degrade the substrate and promote fermentation processes [19,20]. However, the LAB and other acidogens in the FW or seed sludge adversely affect the hydrogen production processes [5]. Under certain conditions, these indigenous microorganisms can selectively accumulate in the fermenters and compete with HPBs for substrates, resulting in a lower hydrogen yield [21,22].…”

“…To alleviate these negative effects, various FW pretreatment methods such as heat shock, microwave pretreatment, alkali shock, and acid pretreatment have been reported to inactivate the hydrogen-consuming bacteria [5,19,25]. Ortigueira et al utilized microwave pretreatment to eliminate the microbial counts in FW, and successfully improved the hydrogen yield and productivity [5]. Heat-shock pretreatment was regarded as an effective method to inactivate the LAB and other non-spore-forming microorganisms.…”

Food waste biorefinery: Stability of an acidogenic fermentation system with carbon dioxide sequestration and electricity generation

“…The process start-up was performed as follows: 60.75 g of humid CIW (correspondent to approximately 10 g of total sugars and a final concentration of 20 g L À1 in the bioreactor) were subjected to microwave (MW) pretreatment, as described elsewhere (Ortigueira et al, 2019a). This mixture was suspended in minimum mineral medium as already published (MMM) (per L of phosphate buffer 100 mM: 12 g ammonium chloride, 3.28 mg ferrous sulphate heptahydrate, 0.56 g cysteine hydrochloride monohydrate), up to a total volume of 500 mL and degassed with N 2 for 1 h (Ortigueira et al, 2019a). Clostridium butyricum DSM 10702, from the German Collection of Microorganisms and Cell Cultures (DSMZ, Braunschweig, Germany) was used to inoculate the non-sterile mixture at a volumetric concentration of 5%.…”

“…(De Menna et al, 2018). Anaerobic conversion, particularly dark fermentation (DF), has been suggested as an appropriate bioconversion path for FW (Ortigueira et al, 2019a) as it is able to convert carbohydrates into hydrogen (H 2 or, when produced through the DF process, bioH 2 ), while achieving productivity values of more than 1 m 3 h ¡1 m À3 (Ren et al, 2011). Simultaneously, DF generates organic acids and sludge for which valorisation solutions such as the conversion to bioplastic precursors and the maturation to a nutrient-rich compost, respectively, are well-established (Bazyar Lakeh et al, 2019).…”