Production of Gellan Gum by Sphingomonas paucimobilis on Crude Sweet Whey Using Different Bioreactor Feeding Strategies

Aims: Production of gellan gum by Sphingomoas paucimobilis from whey was optimized by different fermentation techniques.

Study Design: Study the growth behavior of Sphingomoas paucimobilis was cultivated on 40% sweet whey medium in the bioreactor as a batch, fed batch and continuous culture and effect of aeration and agitation speed on gellan production.

Place and Duration of Study: Microbiology Dept., Fac. of Agriculture, Ain Shams Univ., Cairo, Egypt, 2016/ 2017.

Methodology: Using Sphingomoas paucimobilis on sweet whey in the bioreactor as a batch, fed batch (pulsed & continuous) and continuous culture. Among the four levels of air saturation and four levels of agitation speeds.

Results: Using the continuous feeding of sugar sweet whey at 1.53 gl-1h-1during 12 h was favorable than pulsed feeding for gellan production in fed-batch culture. In continuous culture addition of 40% SW at 0.055 h-1 dilution rate (110 ml h-1), the values of gellan parameters recorded by Sphingomoas paucimobilis were 24.34%, 26.54% & 0.337 gl-1h-1 for gellan yield, conversion coefficient and gellan productivity during 24 h. At 28ºC. This technique increments the gellan production (gl-1h-1) by 3.3 & 2.2-2.5 and 1.5- 1.6 fold as compared to that produced by using batch & fed- batch pulsed and fed-batch continuous techniques respectively. The emulsifying capability of the partially purified gellan was 100% whereas it was 95% for xanthan gum, as well as its high flocculating activity than xanthan. A tough worm-like gel or firm gel were formed when 10% calcium chloride solution or 0.5 g sodium chloride were added to gellan solution.

Conclusion: The maximum gellan yield and lower fermentation period were obtained with air saturation of 60% at 750 rpm agitation speed. The continuous feeding at 1.53 gl-1h-1 was favorable than pulsed feeding for gellan production in fed-batch culture, while the maximum gellan productivity was obtained by using a continuous culture technique at 0.055 h-1 dilution rate.