| In the present thesis, physical and nutrient factors that affect the growth of S.platensis Ag were studied systematically for the purpose of increasing the biomass of strain A9 in liquid culture. Effects of physical factors on the growth of strain Ag were of light intensity , temperature, inoculum volume, initial pH, effects of nutrient factors on the growth of strain Ag included organic carbon sources, organic nitrogen sources , growth factors, hormone etc., and the correlation among nutrient factors being considered. The growth condition of single filament on the plate was also studied.Effects of physical factors on the growth of strain Ag were investigated, and suitable growth condition for strain Ag were as follows: light intensity, 25001ux; temperature,30℃; inoculum volume,10%(v/v); pH, about 9.0.In searching for nutrient factors that could increase the growth of strain Ag, experiment were made and conclusion were as follows.Among the organic carbon sources, 2.0g.L~ glucose obviously stimulated the growth of strain A9. Compared with Zarrouk medium without organic carbon sources, average growth ratio increased by 19.1% and average time for one generation shortened almost 16.1% with 2.0g.L-1glucose. Addition of 2.0g.L-1 maltose to Zarrouk medium could also promote the growth of strain A9, especially at the primary and the mid stage of cultivation. Strain Ag also grew better with 1.0g.L-1 sodium hyroxysuccinic. But the growth of strain Ag was intensitively inhabited by sodium startrate.Effects of added organic nitrogen sources in Zarrouk medium were not so obviously as that of organic carbon sources, only 0.6g.L-1 peptone or 0.1g.L-1 urea could advance the growth of strain Ag slightly.Organic carbon and nitrogen sources could not only promote the growth of strain Ag, but also changed the content of phycobioprotein and chlorophyll-a. In the experiment, the content of phycobioprotein in strain Agwas improved with urea addition, and the content of chl-a increased in the condition of adding sodium hydroxysuccinic.Effects of nine growth factors as Biotin, Calcium pantothenate, VB12, Folic acid, Inositol, Nicotinic acid, VBI, Thymine, VB6on the growth of strain Agwere investigated. Biotin, VB12, VB1, Nicotinic acid had comparatively distinct improvement . Orthogonal test with these four growth factors indicated that Biotin, VB12, VB1, Nicotinic acid had significant effects on biomass at 95%level, and the optimum combination of growth factors was VB1 0.5mg.L-1, VB12 20ug.L-1. Further experiment for sieving suitable concentration of every single factors, the most suitable concentration for Biotin, VB12, VB1, Nicotinic acid were 5ug.L-1, 20ug.L-1, 25ug.L-1, 70ug.L-1 respectively. It was also found that adding 4mg.L-1 Vcto Zarrouk medium could promote the growth of strain A9.Hormone could advance the growth of strain Ay too, especially at the early six day of cultivation. Results showed NAA , 2,4-D, IBA, IAA, 6-BA and GA stimulated the growth of strain A9 and suitable concentration were 5mg.L-1, 0.5mg.L-1, 1 mg.L-1, 0.5mg.L-1, 1.0 mg.L-1, and 0.5 mg.L-1 respectively. Amidst the six kinds of hormone, NAA, 6-BA, GA, 2,4-D had comparatively satisfied stimulating effect. Intersection experiment with them were made, but only combination of NAA and 6-BA slightly promoted the growth of strain A9. The content of intrinsic hormone GA within strain A9. cultivated for 5 days was 0. 758mg.g-1, while the content of intrinsic hormone GA within strain A9. cultivated for 10 days was 0.542mg.g-1. Determination of intrinsic hormone offered theoretic basis for the effect of hormones on the growth of strain A9.The major affecting factors such as glucose, optimized growth factors , Vcand growth hormone were further combined by means of orthogonal test and the optimum medium for mixotrophic growth was: with glucose 1.5g.L-1, VB1 250ug.L-1, VB12 10ug.L-1 , NAA 0.5mg.L-1 .in Zarrouk medium. Compared with strain A9 cultivated in Zarrouk, the biomass of strain A9 grew under optimum chemically defined medium increas... |
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