الفهرس 
Nutritional factors.Only 14 pages are availabe for public view
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Abstract
Growing interest in fatty acids and oil was resulted in the development of fermentation technologies to produce microbial oils. The main objectives of this research were to investigate the nutrient requirements including media composition and cultivation requirements for Candida lipolytica NRRL Y-1095 and Rhodotorula glutinis ARC Y-54 on some agro-industrial by-products for single cell oil (SCO) production in a low cost medium.
Obtained results can be summarized as follow :
I. Selection of productive medium and yeast strains :
Five cultivation medium were used together with ten yeast strains. The programme used in this part proved that cultivation medium No.3 was the favourable medium for microbial production after replacing both C- source and N- source by some agro-industrial by-product.
Results showed also that Candida lipolytica NRRLY-1095 and Rhodotorula glutinis ARC Y-54 were the most productive strains for microbial oil in agro-industrial by-product containing cultivation medium.
II. Optimization for microbial oil production :
Optimization for single cell oil (SCO) was carried out on the level of nutritional and cultivation factors. For the nutritional factors, the carbon source, carbon concentration, nitrogen source, nitrogen concentration, and addition of NaCl were individually examined. Concerning the cultivation parameters, the growth temperature, incubation period, cultivation medium pH, agitation speed and cell immobilization were also individually tested.
Six agro-industrial wastes namely, glucose syrup, sugar cane molasses, beet molasses, potatoes peel, squash peel, and tomatoes peel were individually examined as carbon sources. Six concentrations of carbon sources were tested, these concentrations were 80.0, 100.0, 120.0, 140.0, 160.0, and 180.0gl-1 compared to glucose in 100 gL-1 as control for each tested yeast strain.
Four agro-industrial by-products called corn gluten meal, corn steep liquor, protelan and rice bran were individually tested as nitrogen source, nine concentrations of nitrogen sources were examined. These concentrations were 0.032, 0.065, 0.130, 0.195, 0.260, 0.320, 0.390, 0.455 and 0.520 gl-1 compared to NH4cl in 0.260 gL-1 as control. Seven levels of pHs as initial values of cultivation medium were also performed. These levels were 4.0, 4.5, 5.0, 5.5, 6.0, 6.5 and 7.0 compared to pH 6 as control In addition, six concentrations of NaCl were also tested; 1.0, 3.0, 5.0, 7.0, 10.0 and 15.0% Nacl compared to control without NaCl.
Obtained results showed that among six agro-industrial by-product, sugar cane molasses was the most favorable carbon source for the two tested yeast strain. For N-source, obtained results exhibited that corn gluten and protelan were the favourable sources for Candida lipolytica NRRLY-1095 and Rhodotorula glutinis ARC Y-54, respectively.
Obtained results showed also that 72h, 20ºC, 5.5 and 200 rpm the best conditions for microbial oil production by Candida lipolytica NRRL Y-1095. These results were 48 hr, 20 ºC, 5.5, and 200 rpm the favourable conditions for Rhodotorula glutinis ARC Y-54.
III. Fatty acid composition of obtained microbial oil :
Obtained microbial oil samples were analyzed by GC and obtained data showed that all samples contained number of saturated fatty acids (C:0), monounsaturated fatty acids (C:1), polyunsaturated fatty acids (C:2).
The predominant saturated fatty acid was Palmitic acid C16H32O2 (C16: 0) in all tested oil samples. Oleic acid C18H34O2 (C18:1) was the major one of the monounsaturated fatty acid. Besides, linoleic acid C18H30O2 (C18:2) was the highest incidence fatty acid of polyunsaturated fatty acid. This data proved that obtained microbial oil is closely near to both canola oil and palm oil, too.