Development of palm-oil based growth medium for microbial production of xanthan gum in a stirred-tank bioreactor / Veluri Venkata Purna Satyanarayana Murthy, Miradatul Najwa Muhd Rodhi and Kalavathy Ramasamy

Murthy, Veluri Venkata Purna Satyanarayana and Muhd Rodhi, Miradatul Najwa and Ramasamy, Kalavathy (2010) Development of palm-oil based growth medium for microbial production of xanthan gum in a stirred-tank bioreactor / Veluri Venkata Purna Satyanarayana Murthy, Miradatul Najwa Muhd Rodhi and Kalavathy Ramasamy. Research Reports. Research Management Institute (RMI), Shah Alam. (Unpublished)

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Abstract

Xanthan gum is an important suspending, stabilizing, thickening and emulsifying agent in food and non-food industries. It is currently produced by a bioprocess using an aerobic bacterium Xanthomonas campestris. It has been found that the use of vegetable oils in the fermentation could overcome some problems in xanthan production. Therefore, this research was taken up to study the effect of supplementing the growth medium with palm-oil on xanthan production. Shake flask and bioreactor studies using Rushton and InterMIG impeller were carried out in this research. The fraction of oil used in formulating the growth medium was varied from 0.05 to 0.50 v/v oil. In shake flask studies with 0.50 v/v oil, xanthan concentration was found to increase more than two fold. It was found that the viscosity of xanthan solution could be brought down from 719.85 cP to 225.50 cP as the oil fraction was increased. The apparent viscosity of the xanthan solutions with and without addition of oil decreased as the shear rate increased. The flow behavior index (n) for different xanthan solution and at the oil fraction range of 0.05v/v and 0.15v/v was less than one, which indicated pseudoplastic behavior. There was no significant reduction in the viscosity in the bioreactor studies. Nevertheless, xanthan production could be doubled by the addition of palm-oil. The effect of reusing the oil from previous runs on xanthan production was also evaluated. Xanthan concentration obtained in the fermentation with fresh oil was higher than the fermentation with recycled oil. The utilization of palm-oil as a secondary carbon source by the cells was identified from the lipase activities and glucose consumption rates. The optimum oil fraction in the bioreactor installed with Rushton and InterMIG impellers, at which lipase activities were maximum (0.38 and 0.24 U/mL, respectively), was found to be the same i.e. 0.35 v/v. This shows that the potential of palm-oil as a secondary carbon source. In the fermentation with InterMIG impeller, the xanthan concentration increased from 17.39 g/L to 38.50 g/L in the fermentation with 0.50 v/v oil whereas in the fermentation with Rushton impeller, the maximum xanthan concentration was found to be in the fermentation with 0.25v/v of oil. Fermentation runs using InterMIG impeller were found to give a higher concentration of xanthan gum than those using Rushton impeller. It was also found that xanthan concentration was found to increase with increasing aeration and agitation. It was also observed that the oxygen transfer is higher when the InterMIG impeller is used compared to Rushton impeller. The higher range of kLa and xanthan concentration were found to be around 20 h⁻¹ and 40g/L respectively, at an optimum oil fraction of 0.35 v/v for both the impellers. However, InterMIG impeller was found to consume higher power per unit volume (3.3W/L). FTIR analysis indicated that the properties of xanthan gum produced were nearly the same standard with the food grade xanthan gum.

Item Type: Monograph (Research Reports)
Uncontrolled Keywords: Palm-oil based; Microbial production; Xanthan gum; Stirred-tank bioreactor
Subjects: T Technology > TP Chemical technology > Biotechnology
Divisions: Research Management Institute (RMI)
Depositing User: Staf Pendigitalan 5
Date Deposited: 09 May 2017 09:14
Last Modified: 09 May 2017 09:14
URI: http://ir.uitm.edu.my/id/eprint/16864

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