Xanthan gum characterization and production kinetics from pomace of Vitis vinifera

Abstract

Vitis vinifera (grape) pomace is rich in soluble carbohydrates, which can be valorized as a carbon source in the fermentative production of bio-based products such as xanthan gum. The aim of the present study was to determine the potential use of grape juice by-products as a sole carbon source in the production of xanthan gum by four Xanthomonas strains and evaluate the fermentation kinetics and rheological behavior of the produced gums. In addition, the produced gum was tested in pudding as a model food. Xanthomonas isolates exhibited a higher (6.25%) xanthan gum production than standard strain from grape juice pomace and the highest production was found as high as 5.1 g/L for X. axonopodis pv. vesicatoria isolated from pepper plant. In general, all bacteria exhibited growth associated kinetics for xanthan production and substrate consumption. X. hortorum pv. pelargonii presented the best apparent viscosity at 1% and 2% concentrations with 46 and 14 Pa.s, respectively. Viscosity of pudding sample prepared by commercial gum was found the highest with 254.7 Pa.s. This work showed that grape juice pomace without any pretreatment can be an excellent alternative substrate for industrial xanthan gum production. Novelty Impact Statement Investigation of xanthan gum fementation by Xanthomonas strains from grape pomace can solve many problems in terms of environment protection and cost of raw material. Grape pomace with a high sugar content did not need enzymatic hydrolysis process before fermentation, which made it cheaper carbon source for production of bacterial products. Therefore, this research showed for the first time that xanthan gum can also be produced from grape pomace with a high yield.