Xanthan gum production from waste bread using different Xanthomonas species and determination of quality

In this study, in order to economically utilize from waste breads constituting a significant part of food waste, xanthan gums were produced under optimum conditions with different Xanthomonas isolates and standard producer strain from waste breads, and the rheological, technological properties, chemical composition and utilization possibilities of the obtained gums were investigated. Bread hydrolyzate was diluted and used as the sole carbon source in the xanthan gum fermentation. By using waste bread as a substrate, high efficiency xanthan gum production has been achieved. During fermentation, biomass and polymer production were increased as glucose was decreased in the medium. Xanthan gum production reached maximum levels at 72 hours and remained at the same levels until the end of fermentation. Optimum yields were detected as 12.5 gL-1, 10.3 gL-1, 14.3 gL-1 and 12.9 gL-1 for X. hortorum pv. pelargonii, X. axonoopodis pv. begoniae, X. axonopodis pv. vesicatoria, X. campestris DSM 19000, respectively. While the aqueous solutions of the gums produced by X. campestris DSM 19000 showed the highest viscosity, it was determined that the gums produced by the isolates gave better consistency to the model foods. The highest consistency of aqueous solutions was obtained by gum from standard bacteria with 10.57 Pa.sn at 2% concentration. For instance X. hortorum pv. pelargonii and X. axonopodis pv. begoniae in pudding sample provide better viscosities. It was determined that all the produced gums contain glucose, mannose and glucuronic acid, which are typical monomers of xanthan gum, and show similarity with commercial xanthan gum in this respect. Glucose contents of the gums were changed between 19.88 and 33.60%, while mannose ranged from 2.90 to 6.71%. The pyruvate contents of the gums ranged from 2.17% to 4.82%, the acetic acid contents varied from 3.45% to 7.61% and the average molecular weights ranged from 1.41x106 to 1.76x106 g/mol, with the pyruvate content and molecular weight increase being related to the development of viscosity. As a result; among the isolates used in the study, the best bacteria in terms of amount of gum production from waste breads was X. axonopodis pv. vesicatoria, however, in terms of gum rheological properties X. axonopodis pv. begonia is in the foreground. In addition, the results obtained in our study show that waste breads are potent and promising properties for low cost and efficient xanthan production. Therefore, it can be regarded as a strong candidate for industrial and commercial applications.