Structure of xanthan gum and cell ultrastructure at different times of alkali stress

Abstract

The effect of alkali stress on the yield, viscosity, gum structure, and cell ultrastructure of xanthan gum was evaluated at the end of fermentation process of xanthan production by Xanthomonas campestris pv. manihotis 280-95. Although greater xanthan production was observed after a 24 h-alkali stress process, a lower viscosity was observed when compared to the alkali stress-free gum, regardless of the alkali stress time. However, this outcome is not conclusive as further studies on gum purification are required to remove excess sodium, verify the efficiency loss and the consequent increase in the polymer viscosity. Alkali stress altered the structure of xanthan gum from a polygon-like shape to a star-like form. At the end of the fermentation, early structural changes in the bacterium were observed. After alkali stress, marked structural differences were observed in the cells. A more vacuolated cytoplasm and discontinuities in the membrane cells evidenced the cell lysis. Xanthan was observed in the form of concentric circles instead of agglomerates as observed prior to the alkali stress.

Evaluating comparative β-glucan production aptitude of Saccharomyces cerevisiae, Aspergillus oryzae, Xanthomonas campestris, and Bacillus natto

“…X. campestris showed the largest decrease in pH compared with other microorganisms; the lowest pH of 3.61 was obtained at 72 h. de Mello Luvielmo et al (2016) stated that X. campestris can use glucose and produce carboxylic acids such as tiglic acid, phenylacetic acid, isovaleric acid, 3-methylthiopropionic acid and trans -3-methylthiacrylic acid for up to 72 h. The production of these acids is characterized by a decrease in glucose level in the medium, which continues to decrease until 96 h till the remaining glucose residue reaches 263 ppm.…”

Farmer Friendly Options for Sterilizing Farm Tools for the Control of Xanthomonas Wilt Disease of Banana

“…Reduction in Xvm population on farm tools after insertion into ash could be due the high pH of ash and a possible dehydrating effect from the ash. Structural changes, more vacuolated cytoplasm and discontinuities in the membrane cells that is a sign of cell lysis has been reported in the bacterium cells after alkali stress (Luvielmo et al, 2016). Alkali stress has also been observed to lower the viscosity and weaken the gum structure of Xanthan, a polysaccharide that protects Xanthomonas campestris (Luvielmo et al, 2016).…”

“…Structural changes, more vacuolated cytoplasm and discontinuities in the membrane cells that is a sign of cell lysis has been reported in the bacterium cells after alkali stress (Luvielmo et al, 2016). Alkali stress has also been observed to lower the viscosity and weaken the gum structure of Xanthan, a polysaccharide that protects Xanthomonas campestris (Luvielmo et al, 2016). In soils, wood ash has been reported to increase pH and pore water electrical conductivity, strongly impacting soil bacterial population and community composition (Augusto et al, 2008;Merghache et al, 2018).…”