| Coccomyxa subellipsoidea C-169 is a small elongated non-motile unicellular green algae and eukaryotic photosynthetic organism, isolated in the Antarctic and can adapt to the particularly harsh environment, with extremely low temperatures and alternating long periods of sunlight and darkness. C-169 is considered as a good raw material of biofuels, which has thin walls easy to resolved by an enzymolysis.These features make Coccomyxa subellipsoidea C-169 used in organic waster treatment, and recycling wastewater resource and achieving C-169 biomass to produce biofuels,which is an economical, environmentally friendly, sustainable wastewater treatment. Yeast wastewater is a kind of refractory wastewater of high organic load, high color and low biodegradability, severely restricted the cleaner production of yeast industry. This paper studies nutritional growth charactoristic of Coccomyxa subellipsoidea C-169 and creates a method which can quickly harvest high-cell-density biomass to inoculate large-scale cultivation. Systematically investigated C-169 tolerance to yeast wastewater, and compared the effects of different culture conditions of pretreated yeast wastewater by activated carbon on C-169 growing in algal-bacterial symbiotic system and purification effect of pretreated yeast wastewater.The main experimental results were as follows:1. In the process of nutritional growth charactoristic of Coccomyxa subellipsoidea C-169, C-169 can use glucose and sucrose for heterotrophic and mixotrophic growth. Compared to autotrophic and heterotrophic growth(10 g/L glucose), growth rate of mixotrophic C–169(10 g/L glucose) was the fastest and achieved the highest biomass 5.65 g/L, significantly increased the biomass by 7.79 times in autotrophic growth and 1.86 times in heterotrophic growth, respectively. In the process of investigating C-169 tolerance to glucose concentration(10-60 g/L), both heterotrophic and mixotrophic C-169 has tolerance to 40 g/L glucose. High concentrations of glucose inhibited cell growth of C-169, and glucose concentration of Basal medium can’t significantly(p>0.05) affect heterotrophic growth of Coccomyxa subellipsoidea C-169. Within 10 to 40 g/L glucose, glucose concentration and cell growth of mixotrophic C-169 were positively correlated. Glucose concentration and total fatty acid content of heterotrophic and mixotrophic C-169 were positively correlated, and the highest content was 21.6%, 26.16%, respectively.2. The effects of low nitrogen and phosphorus on cell specific growth rate, biomass dry weight, content and yield of fatty acids, pigments of Coccomyxa subellipsoidea C-169 grown autotrophically divided three stages in Basal and BBM media at open raceway photo-bioreactors were investigated in this study. The results showed the maximal biomass concentration was obtained at 0.22 g/L in open raceway photo-bioreactors at 13-20 degrees. Compared with BBM medium, cell specific growth rate of Coccomyxa subellipsoidea C-169 grown in Basal media was increased 1.92 times. In the first stage, content of linolenic acid in Basal and BBM media reached 36.6%, 53.9%(Total fatty acids),respectively. In second stage, percent of linolenic acid contents of total fatty acids in BBM media with low nitrogen and phosphorus decreased by 32.4%, percent of oleic acid contents increased by 38.5% and percent of total fatty acids content of dry biomass weight increased from 3.99% to 18.18%. Percent of total fatty acids content in mix medium with 1/2 Basal and 1/2 BBM media increased to 20.2%, and growth rate of cells decreased to 0.01 d-1.Chlorophyll C and D in cells were significantly higher than chlorophyll A and B.3. In the process of effects of culture conditions(seeding density, initial concentration of pretreated yeast wastewater, initial p H value) and varies of enhancement means(CO2, acetic acid and glycerin) on C-169 growing in algal-bacterial symbiotic system and purification effect of yeast wastewater, the optimum culture conditions were determined: cell density inoculated yeast wastewater shall not be less than 1g/L; optimization dilution multiple of pretreated yeast wastewater was 2; optimum initial p H value was 5.0. Under optimal conditions, biomass yield of Coccomyxa subellipsoidea C-169 was 0.23 g/(L·d), and removal efficiencies of COD, TN and TP of pretreated yeast wastewater can reach 49.54%, 70.39%, 98.09%, respectively. Compared with the results from aeration with air, the highest biomass yield reached 0.42 g/(L·d), and 2% CO2 supplement could significantly increase the cell specific growth rate by 6.49 times, biomass yield by 10.4 times, and total fatty acid content by 3.45 times. Within 0 to 20 g/L glycerol, cell growth of C-169 and removal efficiencies of TN and TP of pretreated yeast wastewater were increase with increasing glycerol concentration. The highest dry biomass and biomass yield reached 8.80 g/L, 0.70 g/(L·d), respectively. When glycerol concentration was equal or greater than 15 g/L, removal efficiencies of TN and TP of pretreated yeast wastewater reached 85%, 95% or more, respectively. 1-4 g/L glycerin supplement could significantly decrease cell growth of C-169 and removal efficiencies of TN and TP of pretreated yeast wastewater. |
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