RECOVERY OF XANTHAN FROM FERMENTATION BROTHS BY PRECIPITATION IN A STIRRED-TANK

Precipitation of xanthan gum with isopropanol from dehydrated-reconsti tuted fermentation broths was carried out in a stirred tank (0.014 m3) with four impeller types (D/T approximately 0.5). The effects of xant han concentration, stirring speed and broth feeding rate on precipitat ion yields and power drawn, were evaluated The xanthan concentration i n the broth was the most important parameter in determining precipitat ion yields and power consumption. When working with a 30 kg m-3 broth, yields higher than 85% were obtained with the marine propeller and wi th minimal energy expenditure. Similar yields were reached with the Li ghtnin A-310 and Rushton turbines but at higher energy inputs. Curved blade impeller (marine propeller and Lightnin A-310) showed decreased yields as the impeller speed was higher. Flat blade impellers (Rushton and 45-degrees pitched blade turbines) showed an opposite although le ss pronounced trend