Detoxification of model phenolic compounds in lignocellulosic hydrolysates with peroxidase for butanol production from Clostridium beijerinckii

Abstract

In the present study, we investigated the peroxidase-catalyzed detoxification of model phenolic compounds and evaluated the inhibitory effects of the detoxified solution on butanol production by Clostridium beijerinckii National Collection of Industrial and Marine Bacteria Ltd. 8052. The six phenolic compounds, p-coumaric acid, ferulic acid, 4-hydroxybenzoic acid, vanillic acid, syringaldehyde, and vanillin, were selected as model fermentation inhibitors generated during pretreatment and hydrolysis of lignocellulose. The enzyme reaction was optimized as a function of the reaction conditions of pH, peroxidase concentration, and hydrogen peroxide to substrate ratio. Most of the tested phenolics have a broad optimum pH range of 6.0 to 9. Removal efficiency increased with the molar ratio of H(2)O(2) to each compound up to 0.5-1.25. In the case of p-coumaric acid, ferulic acid, vanillic acid, and vanillin, the removal efficiency was almost 100% with only 0.01 microM of enzyme. The tested phenolic compounds (1 g/L) inhibited cell growth by 64-74%, while completely inhibiting the production of butanol. Although syringaldehyde and vanillin were less toxic on cell growth, the level of inhibition on the butanol production was quite different. The detoxified solution remarkably improved cell growth and surprisingly increased butanol production to the level of the control. Hence, our present study, using peroxidase for the removal of model phenolic compounds, could be applied towards the detoxification of lignocellulosic hydrolysates for butanol fermentation.

Production of Biofuels from Cellulose of Woody Biomass

“…It was reported that, during the initial growth phase of cells, other by-products were also produced such as acetic acid and butyric acid, which inhibited the butanol production [84]. In one study, the presence of 1 g/l ferulic acid and vanillin acid reduced the cell growth by 70% and 56%, respectively [84]. The choice of detoxification method would depend on the compositions of hydrolysates and the species of fermenting microorganism [84].…”

“…In one study, the majority of inhibitory compounds were phenolic compounds, while furfural and hydroxymethyl furfural (HMF) did not affect the cell growth and ABE fermentation [84]. It was reported that, during the initial growth phase of cells, other by-products were also produced such as acetic acid and butyric acid, which inhibited the butanol production [84]. In one study, the presence of 1 g/l ferulic acid and vanillin acid reduced the cell growth by 70% and 56%, respectively [84].…”

“…In one study, the presence of 1 g/l ferulic acid and vanillin acid reduced the cell growth by 70% and 56%, respectively [84]. The choice of detoxification method would depend on the compositions of hydrolysates and the species of fermenting microorganism [84]. Previously, lime treatment [85], evaporation, adsorption using ion exchange resins and activated carbon were used prior to fermentation…”

“…as detoxification methods for butanol production [84]. However, the detoxification efficiency depends on the chemical structure of inhibitors [84].…”

Biodetoxification of Lignocellulosic Hydrolysates by Specially Adapted Activated Sludge

“…Physicochemical detoxification methods are carried out by lime treatment (Njoku et al, 2013;Martínez et al, 2000), activated charcoal Berson et al, 2005), evaporation (Palmqvist, & Hahn-Hagerdal, 2000), ion exchange resins (Cho et al, 2009) or nano-filtration (Sun, & Liu, 2010). The general disadvantage of known methods of physicochemical detoxification is their high cost and/or the formation of large amounts of waste, which increases the burden on the environment.…”