Background Hydrogen peroxide (H2O2) has gained attention as cofactor of lytic polysaccharide monooxygenases (LPMOs) during lignocellulose saccharification. The action of these enzymes has been shown to significantly enhance saccharification efficiency. However, in simultaneous saccharification and fermentation (SSF) processes, H2O2 can have deleterious effects on the fermenting microorganism. In addition to oxidative stress, at certain concentration ranges, H2O2 can play a crucial role in redox biology mediating metabolic crosstalk. Indeed, some works have explored the influence of H2O2 and other stress molecules in lipid accumulation. In this study, nine strains from eight different species of Mucoromycota were grown at different sublethal concentrations of H2O2 and two carbon-nitrogen (C/N) ratios. The aim of this study was to investigate whether H2O2 could enhance lignocellulose-based SSF with oleaginous Mucoromycota fungi to produce second-generation biofuels. Therefore, effects of H2O2 concentration, beneficial or deleterious, were identified under different C/N conditions. Results In general, all the strains tolerated H2O2 at much higher concentrations than those commonly used to improve enzymatic saccharification (1-19 mM vs 1-240 µM). Vibrational spectroscopy (mid-infrared and Raman) was used to analyze the biochemical composition of the fungi. The exposure to sublethal H2O2 doses did not increase any metabolite in particular but slightly reduced biomass production at concentrations near the minimal inhibitory concentration (MIC) in some cases. For Lichtheimia corymbifera grown in standard C/N medium, an accumulation of intracellular proteins with oxidative damage was positively correlated to the H2O2 concentration. This was not observed for other strains. The biggest changes in the biochemical composition of the fungal biomass were linked to changes in medium C/N ratios. This included different carbon allocation strategies among the tested species, such as accumulation of lipids and polyphosphates, lipids and saccharides, etc. Conclusions Our results suggest that the Mucoromycota strains used in this study are compatible with H2O2 feeding in lignocellulose-based SSF to enhance efficiency while sustaining minimal risk of oxidative damage. Graphical abstract

Effect of hydrogen peroxide and carbon-to-nitrogen ratio on growth and biochemical profile in oleaginous mucoromycota

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2025年11月12日

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Cristian Bolaño-Losada,
Boris Zimmermann,
Svein Jarle Horn,
Achim Kohler,
Volha Shapaval

摘要

Background

Hydrogen peroxide (H₂O₂) has gained attention as cofactor of lytic polysaccharide monooxygenases (LPMOs) during lignocellulose saccharification. The action of these enzymes has been shown to significantly enhance saccharification efficiency. However, in simultaneous saccharification and fermentation (SSF) processes, H₂O₂ can have deleterious effects on the fermenting microorganism. In addition to oxidative stress, at certain concentration ranges, H₂O₂ can play a crucial role in redox biology mediating metabolic crosstalk. Indeed, some works have explored the influence of H₂O₂ and other stress molecules in lipid accumulation. In this study, nine strains from eight different species of Mucoromycota were grown at different sublethal concentrations of H₂O₂ and two carbon-nitrogen (C/N) ratios. The aim of this study was to investigate whether H₂O₂ could enhance lignocellulose-based SSF with oleaginous Mucoromycota fungi to produce second-generation biofuels. Therefore, effects of H₂O₂ concentration, beneficial or deleterious, were identified under different C/N conditions.

Results

In general, all the strains tolerated H₂O₂ at much higher concentrations than those commonly used to improve enzymatic saccharification (1-19 mM vs 1-240 µM). Vibrational spectroscopy (mid-infrared and Raman) was used to analyze the biochemical composition of the fungi. The exposure to sublethal H₂O₂ doses did not increase any metabolite in particular but slightly reduced biomass production at concentrations near the minimal inhibitory concentration (MIC) in some cases. For Lichtheimia corymbifera grown in standard C/N medium, an accumulation of intracellular proteins with oxidative damage was positively correlated to the H₂O₂ concentration. This was not observed for other strains. The biggest changes in the biochemical composition of the fungal biomass were linked to changes in medium C/N ratios. This included different carbon allocation strategies among the tested species, such as accumulation of lipids and polyphosphates, lipids and saccharides, etc.

Conclusions

Our results suggest that the Mucoromycota strains used in this study are compatible with H₂O₂ feeding in lignocellulose-based SSF to enhance efficiency while sustaining minimal risk of oxidative damage.

Graphical abstract