Abstract
This study evaluated the individual and combined effects of inhibitory compounds formed during pretreatment of lignocellulosic biomass on the growth of Bacillus subtilis. Ten inhibitory compounds commonly present in lignocellulosic hydrolysates were evaluated, which included sugar degradation products (furfural and 5-hydroxymethylfurfural), acetic acid, and seven phenolic compounds derived from lignin (benzoic acid, vanillin, vanillic acid, ferulic acid, p-coumaric acid, 4-hydroxybenzoic acid, and syringaldehyde). For the individual inhibitors, syringaldehyde showed the most toxic effect, completely inhibiting the strain growth at 0.1 g/L. In the sequence, assays using mixtures of the inhibitory compounds at a concentration of 12.5% of their IC50 value were performed to evaluate the combined effect of the inhibitors on the strain growth. These experiments were planned according to a Plackett–Burman experimental design. Statistical analysis of the results revealed that in a mixture, benzoic acid and furfural were the most potent inhibitors affecting the growth of B. subtilis. These results contribute to a better understanding of the individual and combined effects of inhibitory compounds present in biomass hydrolysates on the microbial performance of B. subtilis. Such knowledge is important to advance the development of sustainable biomanufacturing processes using this strain cultivated in complex media produced from lignocellulosic biomass, supporting the development of efficient bio-based processes using B. subtilis.
Highlights
Due to its low cost, large availability (181.5 billion tons/year) [1], and sugar-rich composition, lignocellulosic biomass has attracted great interest to be used as a feedstock for the production of a wide range of bio-based products
The aim of this study was to elucidate the individual and combined effects of the inhibitory compounds present in lignocellulosic biomass hydrolysates on the growth performance of B. subtilis
Experimental growth curves and lag phases of B. subtilis grown in varying concentrations of the 10 different inhibitory compounds are shown in Figures 1 and 2
Summary
Due to its low cost, large availability (181.5 billion tons/year) [1], and sugar-rich composition, lignocellulosic biomass has attracted great interest to be used as a feedstock for the production of a wide range of bio-based products. In spite of the potential of lignocellulosic biomass as a source of sugars for bioprocesses, some key problems related to their utilization still must be overcome to accelerate the transition towards a society less dependent on fossil fuels. One of these main problems is due to the fact that sugars present in lignocellulosic biomass are not freely available for biochemical conversion by microorganisms. Pretreatment is not a selective reaction, and besides solubilizing hemicellulose sugars, it promotes the formation and release of several other compounds from the lignocellulose structure, which have negative effects on fermentation, affecting the microbial metabolism and reducing the efficiency of the strain to convert sugars into products
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