Biohydrogen production with a degenerated strain of Clostridium acetobutylicum ATCC824 from Eichhornia crassipes biomass

Abstract

Degenerate strains of Clostridium acetobutylicum lack the ability to produce solvents and sporulate and remain in a permanent acidogenic state, allowing continuous hydrogen and organic acid production through anaerobic fermentation. Eichhornia crassipes, an invasive aquatic plant, emerges as a promising source of fermentable sugars for hydrogen production via anaerobic fermentation. In this study, a degenerated strain of Clostridium acetobutylicum was isolated and subsequently cultivated in the presence of a hydrolysate solution obtained from the alkaline pre-treatment and enzymatic hydrolysis of Eichhornia crassipes. The hydrolysate was mixed with a defined medium and served the dual purpose of providing essential nutrients and mitigating inhibitors, eliminating the need for an additional detoxification step. A pure defined culture medium served as a control. The extraction methods employed led to the release of low concentrations of inhibitors, reaching 0.1 g/L of furfural and 0.18 g/L of HMF. Kinetic characterization revealed that in the presence of Eichhornia crassipes hydrolysate, the degenerate strain exhibited lower specific growth rates ranging from 0.114 to 0.156 h⁻¹, compared with the control medium which ranged from 0.131 to 0.179 h⁻¹. This was accompanied by lower yields, ranging from 0.115 to 0.167 gDCW/g in the presence of hydrolysate versus 0.178 to 0.190 gDCW/g in the control medium, and diminished butyric acid production of 1.318 to 2.932 g/L in the presence of hydrolysate versus 1.749 to 3.471 g/L in control cultures. Despite reduced growth, high biohydrogen volumetric productivity was achieved, reaching 7.3 L/L·d, along with a significant yield of 2.642 mol of hydrogen per mole of glucose consumed. This represents 66.05% of the maximum stoichiometric yield calculated when acetic acid is the sole byproduct. Apparently, the presence of low concentrations of furfural and HMF released during the pre-treatment of Eichhornia crassipes not only negatively affects growth capacity but also diminishes butyric acid production, favoring biohydrogen production.

Full text

https://doi.org/10.1007/s12155-024-10723-w
Biohydrogen production withadegenerated strain ofClostridium
acetobutylicum ATCC824 fromEichhornia crassipes biomass
PaulinaAguirre1 · PaolaGerman1· KarloGuerrero2
Received: 7 November 2023 / Accepted: 23 January 2024
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024
Abstract
Degenerate strains of Clostridium acetobutylicum lack the ability to produce solvents and sporulate and remain in a per-
manent acidogenic state, allowing continuous hydrogen and organic acid production through anaerobic fermentation. Eich-
hornia crassipes, an invasive aquatic plant, emerges as a promising source of fermentable sugars for hydrogen production
via anaerobic fermentation. In this study, a degenerated strain of Clostridium acetobutylicum was isolated and subsequently
cultivated in the presence of a hydrolysate solution obtained from the alkaline pre-treatment and enzymatic hydrolysis of
Eichhornia crassipes. The hydrolysate was mixed with a defined medium and served the dual purpose of providing essential
nutrients and mitigating inhibitors, eliminating the need for an additional detoxification step. A pure defined culture medium
served as a control. The extraction methods employed led to the release of low concentrations of inhibitors, reaching 0.1 g/L
of furfural and 0.18 g/L of HMF. Kinetic characterization revealed that in the presence of Eichhornia crassipes hydrolysate,
the degenerate strain exhibited lower specific growth rates ranging from 0.114 to 0.156 h−1, compared with the control
medium which ranged from 0.131 to 0.179 h−1. This was accompanied by lower yields, ranging from 0.115 to 0.167 gDCW/g
in the presence of hydrolysate versus 0.178 to 0.190 gDCW/g in the control medium, and diminished butyric acid production
of 1.318 to 2.932 g/L in the presence of hydrolysate versus 1.749 to 3.471 g/L in control cultures. Despite reduced growth,
high biohydrogen volumetric productivity was achieved, reaching 7.3 L/L·d, along with a significant yield of 2.642 mol of
hydrogen per mole of glucose consumed. This represents 66.05% of the maximum stoichiometric yield calculated when
acetic acid is the sole byproduct. Apparently, the presence of low concentrations of furfural and HMF released during the
pre-treatment of Eichhornia crassipes not only negatively affects growth capacity but also diminishes butyric acid produc-
tion, favoring biohydrogen production.
Keywords Anaerobic fermentation· Hydrogen production· Bioenergy· Water hyacinth· Lignocellulosic waste· Plant
valorization· Fermentation inhibitors
Introduction
Molecular hydrogen (H2) has emerged as a promising energy
source due to its exceptional energy density of 122 kJ/g and
its unique property of producing only water vapor upon oxi-
dation [1]. Hydrogen production from non-renewable fossil
fuels is a traditional and widely used method, and about 96%
of hydrogen is produced through natural gas steam reform-
ing, coal gasification, and light oil conversion [2]. The main
advantages of hydrogen production from fossil fuels lie in
high production efficiency and well-developed industrial pro-
cedures. However, adverse factors, including high cost, low
energy conversion, and significant environmental pollution,
are increasingly raising concerns in society [3]. To expedite
the shift toward sustainable energy, there is a growing call to
increase hydrogen production from renewable sources [4].
An interesting alternative for hydrogen production is a
biological approach, which has the potential to utilize renew-
able biomass and even revalorize plant residues [5]. Hydro-
gen obtained through biological means, commonly known as
biohydrogen, is considered a more environmentally friendly
* Paulina Aguirre
piaguirre@utpl.edu.ec
Karlo Guerrero
kguerrerom@utem.cl
1 Departamento de Química, Universidad Técnica Particular
de Loja, Loja, Ecuador
2 Departamento de Biotecnología, Universidad Tecnológica
Metropolitana, Santiago, Chile
/ Published online: 3 February 2024
BioEnergy Research (2024) 17:1770–1783
Content courtesy of Springer Nature, terms of use apply. Rights reserved.