Extractive detoxification of hydrolysates with simultaneous formation of deep eutectic solvents

The hydrolysis of lignocellulosic biomass results in the production of so-called fermentation inhibitors, which reduce the efficiency of biohydrogen production. To increase the efficiency of hydrogen production, inhibitors should be removed from aqueous hydrolysate solutions before the fermentation process. This paper presents a new approach to the detoxification of hydrolysates with the simultaneous formation of in-situ deep eutectic solvents (DES). In the first stage of the study, inhibitors were identified in the real hydrolysate samples using high-performance liquid chromatography (HPLC). Four monoterpenes were tested for their potential to extract furfural (FF) with simultaneous DES formation. An optimization process of the most important parameters affecting the extraction process and DES formation (Thymol:FF) was conducted using the Central Composite Design (CCD) model. A temperature of 40 degrees C, pH of 7, m(HBD) : m(HYD) ratio of 2:1, and time of 50 min were selected as the optimal conditions. These results indicate the high efficiency of FF removal from hydrolysates (92.1-94.6%) in a one-step process. Meanwhile, the structural properties of the formed DES measured by Fourier-transform infrared spectroscopy (FT-IR) and Nuclear magnetic resonance spectroscopy (NMR) differed only slightly from those of the DES composed of pure substances (Furfural and Thymol).