Abstract:Aims:The objective of this study was to evaluate the inhibitory activity of compounds secreted by bacteria isolated from a hydrogen-producing bioreactor to understand how these microorganisms interact in this community.
Methods and Results:In vitro inhibitory assays were performed using samples secreted by bacteria subject to different treatments to determine if their inhibitory effect was due to organic acids, non-proteinaceous compounds or bacteriocin-like inhibitory substances (BLIS). Bacterial isolated wer… Show more
“…On the other hand, the lactic acid bacterium Lactobacillus has also been reported in hydrogen-producing reactors via CBP (Ayala-Campos et al 2022 ; Pérez-Rangel et al 2023 ). These two LAB seem to establish different interactions with hydrogen producers; for example, Pérez-Rangel et al ( 2022 ) reported antagonism between Lactobacillus – Enterococcus and Enterococcus – Clostridium , but not between Lactobacillus – Clostridium . Notably, in those processes where Lactobacillus and Clostridium thieved together, there was no accumulation of lactic acid, which strongly suggests the occurrence of the lactic acid-based pathway.…”
Lactic acid bacteria (LAB) coexist with Clostridium spp. in hydrogen production processes from complex substrates; however, the role of LAB is still unclear. This study analyzed the fermentation products in a wide range of initial pH (pHi, 5.5–6.9) and total solids (TS%, 8–22%) to determine the activity of these two microbial groups over time (from 24 to 120 h). Agave bagasse served as the feedstock for hydrogen production via consolidated bioprocess (CBP), while the inoculum source was the indigenous mature microbiota. In the early stage of the CBP, hydrogen production from lactic acid occurred only at pHi ≥ 6.0 (ρ = 0.0004) with no effect of TS%; lactic acid accumulated below this pHi value. In this stage, lactic acid production positively correlated with a first cluster of LAB represented by Paucilactobacillus (r = 0.64) and Bacillus (r = 0.81). After 72 h, hydrogen production positively correlated with a second group of LAB led by Enterococcus (r = 0.71) together with the hydrogen producer Clostridium sensu stricto 1 (r = 0.8) and the acetogen Syntrophococcus (r = 0.52) with the influence of TS% (ρ < 0.0001). A further experiment showed that buffering the pH to 6.5 increased and lengthened the lactic acid production, doubling the hydrogen production from 20 to 41 mL H2/gTSadded. This study confirmed the prevalence of distinct groups of LAB over time, whose microbial activity promoted different routes of hydrogen production.
“…On the other hand, the lactic acid bacterium Lactobacillus has also been reported in hydrogen-producing reactors via CBP (Ayala-Campos et al 2022 ; Pérez-Rangel et al 2023 ). These two LAB seem to establish different interactions with hydrogen producers; for example, Pérez-Rangel et al ( 2022 ) reported antagonism between Lactobacillus – Enterococcus and Enterococcus – Clostridium , but not between Lactobacillus – Clostridium . Notably, in those processes where Lactobacillus and Clostridium thieved together, there was no accumulation of lactic acid, which strongly suggests the occurrence of the lactic acid-based pathway.…”
Lactic acid bacteria (LAB) coexist with Clostridium spp. in hydrogen production processes from complex substrates; however, the role of LAB is still unclear. This study analyzed the fermentation products in a wide range of initial pH (pHi, 5.5–6.9) and total solids (TS%, 8–22%) to determine the activity of these two microbial groups over time (from 24 to 120 h). Agave bagasse served as the feedstock for hydrogen production via consolidated bioprocess (CBP), while the inoculum source was the indigenous mature microbiota. In the early stage of the CBP, hydrogen production from lactic acid occurred only at pHi ≥ 6.0 (ρ = 0.0004) with no effect of TS%; lactic acid accumulated below this pHi value. In this stage, lactic acid production positively correlated with a first cluster of LAB represented by Paucilactobacillus (r = 0.64) and Bacillus (r = 0.81). After 72 h, hydrogen production positively correlated with a second group of LAB led by Enterococcus (r = 0.71) together with the hydrogen producer Clostridium sensu stricto 1 (r = 0.8) and the acetogen Syntrophococcus (r = 0.52) with the influence of TS% (ρ < 0.0001). A further experiment showed that buffering the pH to 6.5 increased and lengthened the lactic acid production, doubling the hydrogen production from 20 to 41 mL H2/gTSadded. This study confirmed the prevalence of distinct groups of LAB over time, whose microbial activity promoted different routes of hydrogen production.
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