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Domenii publicaţii > Stiinte ingineresti + Tipuri publicaţii > Tezã de masterat (nepublicatã)
Autori: Camelia Ungureanu
Facing the growing economic significance of carotenoids, much interest has been devoted to new supplies of this type of pigment. In particular, the development of carotenoid-producing microorganisms is new regarded as a competitive pathway since they can provide natural and original pigments such as torularhodin and β-carotene produced by Rhodotorula glutinis (Sakaki et al. 2000, Bhosale & Gadre 2001) or astaxanthin from Phaffia rhodozyma (Yamane et al. 1997, Reynders et al. 1997).
Recently, raw material and by-products of agro industrial origin have been proposed as low cost alternative carbohydrate sources for microbial metabolite production. To improve the carotenoid production from Phaffia rhodozyma , the use of inexpensive substrates such as corn wet-milling co-product (Hayman et al. 1995), and peat hydrolysates (Martin et al. 1993) have been studied. Also, there were several reports on cultivation of yeasts favourable carbon source when present in a rich medium (containing peptone and yeast extract) to produce pigments. To our knowledge, only few microorganism are able to groe on technical glycerol. The salts released from the oil transesterification, diluted in technical glycerol, exert significant inhibitory effects on many microorganism. Technical glycerol is a by-product and can become an important feed stock when bio-diesel is applied on a large commercial scale.
Many microorganisms are able to synthesize carotenoids for industrial using. The aim of the present work is to study the production of an uncommon red pigment by a quasi-unknown yeast growing in an inexpensive liquid medium. This study is divided mainly into three parts: the first one describes how a new strain of Sporobolomyces, SP. ruberrimus H110, was isolated and identified. The second part contains used methods and materials and especially is dealing with the breaking of the cell wall when using different chemical and physical methods. Among the methods tested, the crushing of the cells was the most efficient to recover the pigment by further ethanol extraction.
In the last part, after the carbon source choice done, the kinetic parameters of the yeast growth and pigment production were determined when varying nature and concentration of fatty acids (carbon source) notably. Thus, technical glycerol is uptaken by the new strain to produce about 35 g dry cells L-1 and 3.7 mg torularhodin g-1 of cells that is to say 130 mg.L-1 in non-optimal culture conditions. One of the interests of this strain use is that torularhodin represents about 95% of total carotenoids.
Cuvinte cheie: Torularhodin, Sporobolomyces ruberrimus, glycerol, fatty acids // Torularhodin, Sporobolomyces ruberrimus, glycerol, fatty acids