Enhanced hydrogen production from food waste via bioaugmentation with Clostridium and Lactobacillus

Abstract Dark fermentation (DF) of food waste (FW) is a promising and sustainable alternative for valorization, where a carbohydrate-rich substrate is converted into value-added products such as hydrogen (H 2 ) and volatile fatty acids (VFA). In this work, several combinations of hydrogen-producing bacteria ( Clostridium butyricum and Clostridium beijerinckii ) along with lactic acid bacteria ( Lactobacillus plantarum and Lactobacillus pentosus ) were evaluated for H 2 production using sterile FW as a substrate in DF batch tests as follows: 10% v/v inoculum ratio, 10 g VS L −1 of FW, phosphate buffer pH 7.4 (0.005 M), 37 °C, and 150 rpm. The highest H 2 production of 46.0 ± 0.7 mL H 2 g VS −1 was obtained by the combination of C. butyricum (61%), C. beijerinckii (13%), L. plantarum (13%), and L. pentosus (13%), showing a synergistic activity between those strains. Subsequently, this combination was tested to carry on a bioaugmentation strategy using sterile and non-sterile FW as substrate, achieving an H 2 production of 89.6 ± 1.0 mL H 2 g VS –1 and 76.7 ± 2.6 mL H 2 g VS –1 with sterile and non-sterile FW, respectively. According to the microbial analysis, Lactobacillus species were displaced in the microbial community, and Clostridium sensu stricto 1_butyricum led the H 2 production in both sterile and non-sterile FW tests. The results suggest that a negative interaction was established between C. butyricum and Enterobacter , generating low H 2 production during fermentation with non-sterile FW. This study confirms that bioaugmentation with hydrogen-producing microorganisms is a promising alternative for valorizing feedstocks, such as FW, which tend to be predominated by lactic acid bacteria.