Adsorption of Fermentation Inhibitors by Layered Double Hydroxides in Synthetic Hemicellulose Hydrolysate: A Batch Multicomponent Analysis

Abstract

Studies have been conducted on detoxification of hemicellulose hydrolysates, but an effective detoxification method remains to be developed. The use of layered double hydroxides (LDHs) as adsorbents may be a solution to this problem. In this study, LDHs composed of 30, 63, or 70% MgO were used in their uncalcined and calcined states to adsorb acetic acid, formic acid, hydroxymethylfurfural, and furfural from a synthetic hemicellulose hydrolysate. Kinetic studies revealed that calcined LDH composed of 70% MgO (MG70c) had the best performance: it was able to remove 73% of acetic acid and 90% of formic acid in 6 h of incubation at 50 °C. Hydroxymethylfurfural and furfural were not adsorbed (C/C 0 ≈ 1) by calcined or uncalcined LDHs under the studied conditions. The adsorption equilibrium was determined at different temperatures. Adsorption isotherms were best described by the Langmuir−Freundlich model. These results show the potential of MG70c to remove acetic and formic acids from hemicellulose hydrolysates, thereby increasing their suitability as fermentation substrates.

New Proposal in a Biorefinery Context: Recovery of Acetic and Formic Acids by Adsorption on Hydrotalcites

“…Previous studies reported that adsorption increases with increasing availability of active sites. 50,51,57 MG30c had fewer negative sites (1.677 mmol negative charge g −1 ) than MG63c and MG70c (3.636 and 2.924 mmol negative charge g −1 , respectively). A greater number of negative sites allows higher adsorption of compounds, which explains why MG63c adsorbed more AA and FA than the other hydrotalcites.…”

“…AA and FA concentrations were chosen on the basis of a preliminary experiment, indicating the average composition of hemicellulosic hydrolysates obtained by acid hydrolysis of sugarcane bagasse. 50 Kinetic adsorption experiments were performed in duplicate. Briefly, hydrotalcite (0.036 g) and synthetic hemicellulosic hydrolysate (1.2 mL, solid fraction = 30 mg mL −1 ) were mixed, and samples were incubated in a thermoblock at 30 °C and 1500 rpm.…”

“…Adsorbents were previously characterized by our research group. , MG30c, MG63c, and MG70c contain 28.8, 62.9, and 70.7% MgO, respectively. MG63c exhibits the largest number of active sites, followed by MG70c and MG30c (3.636, 2.924, and 1.677 mmol negative charge g –1 , respectively).…”

Enzymatic removal of inhibitory compounds from lignocellulosic hydrolysates for biomass to bioproducts applications

“…Combining other detoxification treatments with enzymatic detoxification is recommended for overall process improvements (Geddes et al 2015). For instance, to include the application of adsorbents, redox mediators, media alkalinization, and others, for the removal of all types of ICs (Moreno et al 2015;Geddes et al 2015;Travália et al 2019).…”

“…The cell-inhibitory effects of weak acid ICs are related to the reduction of the intracellular pH, accumulating anions in the cell and causing the reduction of ATP production (Jönsson et al 2013). The weak acids can be removed from hydrolysates through layered double hydroxides (LDHs) as adsorbents, amongst other techniques (Jönsson and Martín 2015;Travália et al 2019).…”