Optimization of Alkaline Extraction of Xylan-Based Hemicelluloses from Wheat Straws: Effects of Microwave, Ultrasound, and Freeze–Thaw Cycles

Abstract

The alkaline extraction of hemicelluloses from a mixture of three varieties of wheat straw (containing 40.1% cellulose, 20.23% xylan, and 26.2% hemicellulose) was analyzed considering the following complementary pre-treatments: freeze–thaw cycles, microwaves, and ultrasounds. The two cycles freeze–thaw approach was selected based on simplicity and energy savings for further analysis and optimization. Experiments planned with Design Expert were performed. The regression model determined through the response surface methodology based on the severity factor (defined as a function of time and temperature) and alkali concentration as variables was then used to optimize the process in a multi-objective case considering the possibility of further use for pulping. To show the properties and chemical structure of the separated hemicelluloses, several analytical methods were used: high-performance chromatography (HPLC), Fourier-transformed infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (1H-NMR), thermogravimetry and derivative thermogravimetry analysis (TG, DTG), and scanning electron microscopy (SEM). The verified experimental optimization result indicated the possibility of obtaining hemicelluloses material containing 3.40% glucan, 85.51% xylan, and 7.89% arabinan. The association of hot alkaline extraction with two freeze–thaw cycles allows the partial preservation of the hemicellulose polymeric structure.

Reinforcement Fiber Production from Wheat Straw for Wastepaper-Based Packaging Using Steam Refining with Sodium Carbonate

“…Consequently, the diminished fiber yield at higher treatment intensities may be be partially compensated by the heightened biogas potential. Another approach to a more holistic utilization of the raw material involves an integrated processing strategy, wherein hemicelluloses are extracted before pulping-either through hot water or alkaline extraction methods [47,48].…”

Sunflower meal valorization through enzyme-aided fractionation and production of emerging prebiotics

“…In the preliminary experiment, extraction of xylan was performed using most frequently utilized method of alkaline treatment, based on previously published literature data on xylan extraction (22). However, this method proved to be unsuccessful since product with low purity of the isolated xylan was obtained (with 61.5% of DM being proteins), most probably due to complex composition of SFM that includes proteins and other carbohydrates.…”

“…Conventional extraction methods to valorize carbohydrate fraction in different by-products and waste materials, based on multi-step extractions using acids and alkalis, come with many limitations such as loss in ber functionality and laborious operation with low extraction e cacy and, more importantly, environmental unacceptability, since the rigid lignocellulose structure requires severe pretreatments to facilitate e cient extraction of mentioned fractions (17). Pectic compounds are usually extracted using mineral or organic acids (18, 19), while traditional hemicellulose extraction methods are mostly based on alkaline extraction (sodium or potassium hydroxides) of xylan, with or without deligni cation step (20)(21)(22). Deligni cation is usually provided with sodium chlorite, hydrogen peroxide or peroxyacetic acid, with the aim of obtaining purer xylan fractions, since alkaline treatment also partially solubilizes present lignin (23).…”

Ultrasound-Assisted Cold Alkaline Extraction: Increasing Hemicellulose Extraction and Energy Production from Populus Wood

“…There are numerous scientific investigations on the extraction of hemicellulosic derivatives using various alkaline processes, both with and without ultrasound assistance [32,33]. In this work, we combined a cold alkaline treatment with ultrasound technology.…”