Optimization of Total Carotenoid Production by Halorubrum Sp. TBZ126 Using Response Surface Methodology

Abstract

Carotenoids are one of the most diverse and broadly distributed classes of pigments in nature with a high number of biotechnological applications. Carotenoids have a broad range of functions, especially in relation to human health and their role as biological antioxidants. The increasing demand for consumption of natural carotenoids has raised interest in their bio-production. The objective of the present study was the analysis of environmental factors (temperature, pH and salinity) through response surface methodology (RSM) on the total carotenoid production of Halorubrum sp. TBZ126. In addition the effect of light was evaluated. Five levels of temperature, pH, and salinity were selected based on central composite design (CCD) and RSM to reach the optimum values for the cell growth and carotenoid production. Bio-production was carried out in an orbital shaker using a 10% (v/v) inoculum, and agitation at 120 rpm for 9 days in a non-illuminated environment. Dry cell weight was determined and total carotenoid was estimated by spectrophotometer. The production of biomass ranged from 0.04 to 0.84 g/l and the total carotenoid from 0.15 to 10.78 mg/l. The optimum conditions for cell growth and total carotenoid production in Halorubrum sp. TBZ126 cultures, were temperature 31oC and 32oC, pH 7.51 and 7.94 and NaCl (w/v) 18.33% and 20.55%, respectively. In conclusion, employing RSM design and under the light as an inducing factor, carotenoid production by Halorubrum sp. TBZ126 was elevated to about 145%. Additionally, TBZ126 could produce carotenoids at lower concentrations of NaCl (as low as 2.5%), in the absence of sodium acetate without elevating magnesium sulfate concentration.