Microbial Production of β-Carotene by Utilization of Agro-Industrial by-Products

Abstract

Beta-carotene, an important fat soluble pigment,is one of the most common carotenoids and the biosynthetic precursor of vitamin A. The current study aimed to produce beta-carotene by effective microorganism, utilizing agro-industrial by-products as cheap material. Three agro-industrial by-products, namely rice bran, molasses, sugar cane bagasse, were used for β-carotene production using three microorganisms: Rhodotorulaglutinis ATCC 4054, Sphingomonaspaucimobilis ATCC 10829, SerratiamarcescensATCC 27117 to choose the best microorganisms which produce high concentration of β-carotene. To optimize physical and nutritional parameters for β-carotene production by Rhodotorulaglutinis ATCC 4054 and Serratiamarcescens ATCC 27117, using statistical approach of Response Surface Methodology (RSM) Followed by scale-up of the operation under optimized conditions. Beta-carotene was optimized using two step approach. First, a quick identification of important factors, like carbon and nitrogen source by simple screening experiment, and second application of complex RSM for further optimization. The optimum conditions for β-carotene production by R.glutinis were; sucrose 18.6g/L, initial pH at 5.4, KH2PO4 1.01g/L and NaCl 0.66 g/L to achieve a β-carotene content from 1.23mg/kg rice bran to 3.20 mg/kg and by S.marcescens were Sucrose 2.5 g/L, peptone 7.8 g/L and pH at 6.7to achieve a β-carotene content from 1.1mg/Lmolasses to 2.24 mg/L. Plackett-Burmanexperimental design (PBD) was used for screening variables to elevated β-carotene production and Central Composite Design was proceeded to obtain main, quadratic and interaction effect of significant factors.

The produced β-carotene after scale-up under optimized conditions was purified and analyzed by Thin layer chromatography, High performance liquid chromatography and Gas chromatography-Mass spectroscopy. The structure of beta-carotene was determined by Fourier transform infrared spectroscopy and Proton magnetic resonance. From quantitative analysis by HPLC, β-carotene had purity 68.2084% compared with standard beta-carotene and the concentration of β-carotene equal 89.06 mg/100g yeast cell.

Keywords:β-carotene, Agro-industrial by-products, Rhodotorulaglutinis, Sphingomonaspaucimobilis, Serratiamarcescens, RSM, Plackett-Burman Design, Central Composite Design, TLC, HPLC, Gas chromatography-Mass spectroscopy, Fourier transform infrared spectroscopy, Proton magnetic resonance.