Xylanase Production by Solid-State Fermentation for the Extraction of Xylooligosaccharides from Soybean Hulls§
Nataša Šekuljica1, Sonja Jakovetić Tanasković2, Jelena Mijalković2, Milica Simović2, Neda Pavlović1, Nikola Đorđević2, Alina Culetu3, Ivana Gazikalović1, Nevena Luković2, Jelena Bakrač1 and Zorica Knežević-Jugović2*
1Innovation Center of Faculty of Technology and Metallurgy, Karnegijeva 4, 11000 Belgrade, Serbia
2University of Belgrade, Faculty of Technology and Metallurgy, Karnegijeva 4, 11000 Belgrade, Serbia
3National Institute of Research & Development for Food Bioresources-IBA, Ancuţa Băneasa 5, 021102 Bucharest, Romania
Received: 2 January 2023
Accepted: 26 July 2023
soybean hulls; xylanase; Penicillium rubens; xylooligosaccharides; renewable materials; solid-state fermentation
Research background. The development of a novel process for the production of xylooligosaccharides based on the 4R concept is made possible by the integration of numerous techniques, especially enzymatic modification, together with the physical pretreatment of renewable materials. This study aims to integrate the use of agricultural wastes for the production of xylanase by a new strain of Penicillium sp. and value-added products, xylooligosaccharides.
Experimental approach. To produce xylanase, a solid-state fermentation was performed using wheat bran as substrate. In order to obtain the most active xylanase crude extract, the time frame of the cultivation process was first adjusted. Then, the downstream process for xylanase purification was developed by combining different membrane separation units with size exclusion chromatography. Further characterization included determination of the optimal pH and temperature, determination of the molecular mass of the purified xylanase and analysis of kinetic parameters. Subsequently, the hydrolytic ability of the partially purified xylanase in the hydrolysis of alkali-extracted hemicellulose from soybean hulls was investigated.
Results and conclusions. Our results show that Penicillium rubens produced extracellular xylanase at a yield of 21 U/g during solid-state fermentation. Using two ultrafiltration membranes of 10 and 3 kDa in combination with size exclusion chromatography, a 49 % yield and 13-fold xylanase purification was achieved. The purified xylanase (35 kDa) cleaved linear bonds β-(1→4) in beechwood xylan at a maximum rate of 0.64 μmol/(min·mg) and a Michaelis constant of 44 mg/mL. At pH=6 and 45 °C, the purified xylanase showed its maximum activity. The xylanase produced showed a high ability to hydrolyze the hemicellulose fraction isolated from soybean hulls, as confirmed by thin-layer chromatography. In the hydrothermally pretreated hemicellulose hydrolysate, the content of XOS with different degrees of polymerization was detected, while in the non-pretreated hemicellulose hydrolysate, the content of xylotriose and glucose was confirmed.
Novelty and scientific contribution. Future research focused on creating new enzymatic pathways for use in processes to convert renewable materials into value-added products can draw on our findings.
§Paper was presented at the 10th International Congress of Food Technologists, Biotechnologists and Nutritionists, 30 November-2 December 2022, Zagreb, Croatia