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Optimization of gellan gum production by Sphingomonas paucimobilis ATCC 31461 with nonionic surfactants using central composite design
- Arockiasamy, Santhiagu, Banik, Rathindra Mohan
- Journal of bioscience and bioengineering 2008 v.105 no.3 pp. 204-210
- Sphingomonas paucimobilis, agitation, bioengineering, fermentation, fermenters, gellan gum, mass transfer, nonionic surfactants, octoxynol, oxygen, pH, polysorbates, temperature, viscosity
- The effect of nonionic surfactants on gellan production by Sphingomonas paucimobilis was studied by the addition of 0.5, 0.75, 1.0, 1.25 and 1.5 g/l surfactants to shake flask culture. The nonionic surfactants Tween 80, Tween 40 and Triton X-100 improved gellan production by S. paucimobilis, and the maximum yield (10.44 g/l) was obtained with Triton X-100 at 0.75 g/l compared with that of the control fermentation (8.63 g/l) without surfactant. The DO profiles associated with gellan production in a 5-l laboratory fermentor showed higher oxygen and mass transfers during fermentation with surfactant than during control fermentation without surfactant. The addition of surfactant also resulted in a polymer with high viscosity as manifested by its lower acetyl content, than that obtained by control fermentation. A central composite design (CCD) was used to determine the maximum gellan production at optimum values for three process parameters (Triton X-100 concentration, pH, and temperature) each at five levels in a laboratory fermentor. The maximum gellan yield (14.62 g/l) was obtained in a 5-l laboratory fermentor with 1.0 g/l Triton X-100 and at pH 6.0 and temperature 29.6°C. Further studies on the effects of agitation and DOT level demonstrated that the surfactants enhanced oxygen transfer resulting in higher gellan production (27.86 g/l) at higher agitation speed (1000 rpm) and 100% DOT level.