Tag Archives: β-galactosidase

Production and physicochemical characterization of xanthan gum by native lactose consuming isolates of Xanthomonas citri subsp. citri

R. Moravej1, S. M. Alavi2, M. Azin3, A. H. Salmanian2

1Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran;
2Department of Plant Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB), Tehran, Iran;
3Department of Biotechnology, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran;
e-mail: mealavi@nigeb.ac.ir

Received: 30 September 2019; Accepted: 29 November 2019

Xanthan is a biopolymer produced by Xanthomonas bacteria which is widely used in many industries such as food and oil. In this work, three Xanthomonas strains (X. citri/NIGEB-88, X. citri/NIGEB-386 and X. citri/NIGEB-K37) were used to evaluate their industrial potential to produce xanthan gum in whey medium. Bacteria growth rate, viscosity, biomass, dry weigh of produced xanthan and β-galactosidase activity were studied during the fermentation process and the presence of β-galactosidase genes was assessed by PCR technique. Strain NIGEB-386 had the best ability to utilize lactose in the whey medium. The highest amount of xanthan production and viscosity were 22.7 g/l and 2066.6 mPa·s, respectively. The presence of six β-galactosidase genes in strains NIGEB-386 and NIGEB-K37 was confirmed. The pyruvate and acetyl contents in xanthan gum were 2.1 and 0.29 %, respectively. Fourier-transform infrared spectroscopy analysis determined the position of the functional groups in the structure of the fermentation product. In whey medium, the performance of both NIGEB-386 and NIGEB-K37 strains were better than the X. campestris. The findings showed that Xanthomonas citri/NIGEB-386 is suitable for industrial production of xanthan using cheese whey as a low-cost medium.