Xanthan gum production by the wild strain of Xanthomonas spp. using whey as fermentation substrate

Abstract

Xanthan gum is a microbial biopolymer of great importance in the food industry. The production of this polysaccharide is directly influenced by the cultivation conditions, strains and substrates used as sucrose and glucose, which make the process onerous. The search for strains that present a good quantity/quality ratio and for substrates that reduce the cost of production, such as agro-industrial residues, has been the focus of recent research. The present study aimed to produce xanthan gum using whey in partial replacement of sucrose in the fermentation medium, in a ratio of 1:1. The wild strain of Xanthomonas sp. MN37.2, isolated from mango leaf tissue. Control fermentation was carried out with medium containing 50g/L of sucrose. Fermentations were carried out at 28°C, at 180 rpm for 96 hours. The pH dropped from 6.54 to 5.18 during the fermentation process of the strain and the viable cell population increased from 10.15 log CFU/mL to 11.69 log CFU/mL. The gum production yield in the fermentation with the addition of whey was 62.13% when compared to the fermentation with sucrose as the only carbon source, being 30.35 g/L and 48.85 g/L, respectively. Therefore, whey demonstrates potential to be used as a low-cost substrate for obtaining xanthan gum by bacteria of the genus Xanthomonas. However, studies to optimize the formulation of the fermentation medium, as well as control the stages of gum recovery, must be carried out in order to enable the use of this by-product on an industrial scale.