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    A DES or LTTM: Eco-friendly solvent mediums for conversion of biomass to levulinic acid as a key chemical
    (Elsevier, 2024) Nis, Berna; Ozsel, Burcak Kaya; Kaya, Yunus
    In this study, the effect of using environmentally friendly, less toxic, low cost, and easily recyclable deep eutectic solvent (DES) and low-transition temperature mixture (LTTM), which are alternatives to ionic liquids, on the conversion of biomass to levulinic acid (LA) was investigated. The reaction conditions such as temperature, the amount of feedstock, and the water ratio were optimized to ensure maximum product formation in DES (ChClEG)-water medium. The highest amount of LA (143.2 +/- 2.5 mg) under optimum reaction conditions was achieved by using glucose in a newly designed LTTM (SA:EG)-water solvent medium. Newly designed low-transition temperature mixture (SA:EG) characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and differential scanning calorimetry (DSC) analyses. A comprehensive theoretical study was also performed to provide a deep understanding of the formation mechanisms of new LTTM by density functional theory (DFT), reduced density gradient (RDG), frontier molecular orbitals (FMOs), and molecular electrostatic potential (MEP) methods. The glucose conversion ratio increased from 70.2 % to 96.1 % in SA:EG-water medium. When microcrystalline cellulose, corn straw, and sorghum were used under the same conditions, 118.9 +/- 5.4, 36.8 +/- 9.4, and 32.6 +/- 3.4 mg of LA were obtained per g of feedstock. A typical Br & oslash;nsted acid; phosphotungstic acid (H3O40PW12) showed high catalytic activity, resulting in 229.0 +/- 0.32 mg of LA per g of glucose in SA:EG-water medium. This shows that the use of SA:EG LTTM for cellulosic/lignocellulosic biomass sources can be used favorably in conversion reactions.
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    EFFICIENT PRETREATMENT OF CORN STRAW AND SORGHUM WITH LTTM FOR ENHANCED BIO-CONVERSION
    (Konya Teknik Univ, 2025) Cataloluk, Ahmet; Demirli, Harun; Nis, Berna; Ozsel, Burcak Kaya
    This study explores using a low transition temperature mixture (LTTM), containing sulfamic acid and ethylene glycol for the pretreatment of corn straw and sorghum biomass, aimed to improve the efficiency of converting biomass into platform chemicals. We first optimized the pretreatment conditions (solid-liquid ratio, temperature, and time) and assessed the conversion of pretreated biomass into 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) using the catalyst Amberlyst-15. Optimal pretreatment conditions were found to be a solid-liquid ratio of 1:5 (w/w), a temperature of 40 degrees C, and a duration of 4 hours, which resulted in the highest yields of sugars; xylose, glucose, and sucrose. In the catalytic conversion of sorghum and corn straw pretreated with LTTM at 200 degrees C in the presence of Amberlyst-15, 801.2 ppm glucose and 1967.3 ppm levulinic acid were obtained from sorghum, while 663.9 ppm glucose and 1936.3 ppm levulinic acid were produced from corn straw. The study demonstrates that LTTMs offer effective and sustainable biomass pretreatment, improving the accessibility of lignocellulosic structure to catalysts, leading to higher yields of desired products like glucose and levulinic acid.
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    Organic acids production from low-cost cellulosic substrates by fermentation
    (Springer Science and Business Media Deutschland GmbH, 2024) Meryemo?lu, Bahar; Nis, Berna; Ozsel, Burcak Kaya
    Lignocellulosics have potential to be used as raw materials in the production of a wide range of chemicals. It is important to develop a sustainable bioprocess for organic acids derived from these sources. The present study aimed to produce organic acids from wheat straw and cotton linter biomass materials by fermentation. As an initial step, the fermentation conditions (sugar, yeast concentration, and time) were optimized for the production of organic acids in a higher yield using cellulose as a feed material. Organic acids were quantified with different liquid chromatography techniques. Many organic acids were identified in biomass hydrolysates after fermentation, lactic and butyric acid were the main acids found to be in 122.6–478.9 and 121.0–482.2 mg/g biomass range, respectively. The elution profiles of organic acids were performed with an LC-TOF/MS system by using three different columns for a comparison of the results obtained with HPLC-RID. Furthermore, the use of various methods and perspectives on difficulties and opportunities in organic acid analysis was discussed. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023.