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In this work, we studied the possibility to use date juice for xanthan gum production by Xanthomonas campestris NRRL B‐1459. The results showed that this strain has a high ability to metabolize date juice. The data on optimization of physiological conditions of fermentation, pH, temperature, inoculum's size, glucose and nitrogen concentration showed that the maximum xanthan yield of 24.5 g/L was obtained from 60 g/L glucose, 3 g/L ammonium sulphate when batch fermentation was carried with 5% inoculum's size at pH 7, 28C, 48 h, on a rotary orbital shaker at 180 rpm. The polysaccharide purified by high performance liquid chromatography and analyzed by thin layer chromatography contained glucose, glucoronic acid and mannose. PRACTICAL APPLICATIONS Agri‐food by‐products rich in sugars may be used to produce high added value food ingredients such as xanthan gum. No work has studied the production of this polysaccharide from date. This study is focused on given value addition to date by‐product (hard texture) by production of xanthan gum. The effect of several parameters (pH, temperature, inoculum's size, agitation speed, nitrogen source and carbon concentration) on production yield was investigated.

Rheological and thermal properties of xanthan produced by Xanthomonas campestris from date by‐products (DBP‐xanthan) and commercial xanthan were determined. DBP‐xanthan gave solutions with lower apparent viscosity than commercial xanthan. However, DBP‐xanthan solutions were more stable to temperature changes and ionic strength than commercial xanthan. Gradual increase of storage modulus (G′) as function of frequency was observed for the two polysaccharides. On the other hand, loss modulus (G″) remained constant for DBP‐xanthan and an increase was observed for commercial xanthan. Granulometric profile indicates that DPB‐xanthan particle size was lower than commercial xanthan. Differential scanning calorimetry showed that the melting temperatures (Tm) and enthalpy (ΔHm) of DBP‐xanthan were higher than those of commercial xanthan. These properties of DBP‐xanthan are quite rare among xanthan described in the literature and give this new gum great potential for use in the field of bioindustries as thickening and stabilizing agents. PRACTICAL APPLICATIONS Xanthan gum from date by‐products (DBP‐xanthan) was recently produced in our laboratory. No work has been undertaken to study the rheological properties of this polysaccharide to date. Rheological and some physicals properties were compared to those of commercial xanthan. This could promote industrial use of DBPs as low‐cost natural source for xanthan gum production.