DETERGENTS IMPROVE XANTHAN YIELD AND POLYMER QUALITY IN CULTURES OF XANTHOMONAS-CAMPESTRIS

The effect of the addition of detergents Tween 40, Tween 80, Chaps, an d Triton X-100 on xanthan fermentation was evaluated in shake flasks. All assessed surfactants, when added after 24 h of culture, improved f inal xanthan gum concentration compared with the control which contain ed no detergent Triton had the most important effect, producing 1.45-f old the gum produced in the absence of detergent. detergent. A time co urse of cultures developed in a 2-l fermentor revealed that the use of Triton led to higher oxygen concentrations during fermentation compar ed with the culture with no detergent. Observations under the microsco pe revealed that the bacterial cells were smaller than those seen in t he absence of the detergent. Compared at the same xanthan concentratio n and ionic strength, the diluted broths of fermentations containing T riton were more viscous than those of a control fermentation. This sug gested that the use of Triton affected factors determining the rheolog ical quality of the polymer such as the molecular weight. The detergen t, when added a posteriori to xanthan broths, did not significantly af fect the viscosity profiles. Since no severe foaming was observed as a result of detergent addition, the use of small amounts of this surfac tant is a promising way for improving xanthan fermentation, thereby al lowing higher xanthan titers and a high quality xanthan gum to be obta ined.