The Assimilation Of Phosphorus And The Utilization Of Beer Wastewater In Chlorella Cultures

In Basal medium, phosphorus is the major nutrients for the cultivation of Chlorella. Phosphorus concentration and the ratio of C/P in this medium have direct effects on the growth of Chlorella and the synthesis of metabolites The phosphorus contents will become a limiting factor for the growth of Chlorella if they are less than that needed, while eutrophication will be caused if their contents excess. Beer wastewater generally contains nontoxic materials such as N, P, and they can cause eutrophication if it was discharged directly. On the other hand, the cultivation of Chlorella consumes a large amount of pure water. Therefore, the combination of these two processes was proposed, and the main results are shown as follows.(1) Five Chlorella strains were screened on Basal medium containing 10 g/l glucose, it was shown that Chlorella pyrenoidosa 15-2070 and Chlorella vulgaris 15-2075 were suitable for heterotrophic mass cultivation according to the growth parameters. The maximum biomass was 5.3 g/l and 5.2 g/l, their maximum biomass appeared at the 3rd day, the specific growth rate was 0.98 /d and 0.96 /d, the cell growth yield on glucose was 0.54 g/g and 0.52 g/g for C. pyrenoidosa and C. vulgaris, respectively.(2) Beer wastewater was used for the cultivation of C. pyrenoidosa. The mixed beer wastewater was used to completely replace distilled water for the preparation of Basal medium containing 10 g/l glucose, on which Chlorella growth had not been restrained and 5.3 g/l biomass was achieved in this medium. It was shown that the mixed beer wastewater could be used as a major component for the heterotrophic of Chlorella. In addition, with appropriate preprocessing to the mixed wastewater, it was shown that the highest removal efficiencies were CODcr, 92.2 %; BOD5, 95.1 %; NO3--N, 98.5 %; NH4+-N, 92.3 % were achieved during the process. For the saccharifying process of wastewater, with appropriate preprocessing to the saccharifying process of wastewater, the increased biomass were 0.3 - 0.6 g/l, and it was shown that the highest removal efficiencies were CODcr,52.4 %;BOD5,24.7 %;total-N,30.0 %;total-P,9.8 %, during the growth of Chlorella, it can deplete some nutriment, but culture and treatment processing need to be optimized further。(3) The effects of various initial PO₄^3--P concentrations from 0 to 284.5 mg/l were investigated on the growth of Chlorella. The results indicated that optimal ratios of carbon-to-phosphorous (C/P) were 206/1 - 2060/1, the cellular assimilation of phosphorus per Biomass Unit (P/B) were 0.8 - 8.1 mg/g for heterotrophic cultivation, and C/P were 103/1 - 2060/1, P/B were 0.8 - 16.1 mg/g for mixotrophic cultivation of C. pyrenoidosa with initial 10 g/l glucose; while C/P were 206/1 - 2060/1, P/B were 0.8 - 8.1 mg/g for both heterotrophic and mixotrophic cultivation with initial 40 g/l glucose; and P/B were 0.8 - 30.0 mg/g for autotrophic cultivation. Temperature, dissolved oxygen, pH and inocula have only effects on the growth of Chlorella, whereas no effects on P/B. Chlorella could be tolerant to high concentrations of phosphate and grows well. The PO₄^3--P concentration in Basal medium was 284.5 mg/l, and this value was in excess of the maximum phosphorus concentration that C. pyrenoidosa absorbed under heterotrophic, mixotrophic and autotrophic cultivation. Thus, the concentration of phosphorus was 62.5-fold higher than that of required for the heterotrophic cultivation with 10 g/l glucose, and there were at least 84.0 % phosphate remained at the end of cultivation.(4) The total cellular phosphorus (TP) was determined using Ion Chromatography when the medium containing various initial PO₄^3--P concentrations from 0 to 284.5 mg/l. TP were at the range of from 1.0 to 10.0 mg/g, the maximum absorbed phosphorus was 10-fold higher than the lowest concentration phosphorus of that required for growth under heterotrophic cultivation; and TP were at the range from 1.0 to 20.0 mg/g, the maximum absorbed phosphorus was 20-fold higher than the lowest concentration phosphorus of that required for growth under mixotrophic cultivation with initial 10 g/l glucose. The excessive phosphorus beyond the required of growth were commonly stored in the cells in the form of polyphosphate. The distribution and accumulation of polyphosphate were investigated by fluorescent microscopy and transmission electron microscope(TEM). The polyphosphate granules were observed in vacuole, and the clearance between cell wall and cell membrane. Chlorella cells containing polyphosphate grew in phosphate-free Basal medium, and the total cellular phosphorus content was 1.0 mg/g at the end of the cultivation.(5) The effects of various initial NO3--N concentrations from 0 to 311.9 mg/l on Chlorella growth were investigated. The results showed that the optimal ratios of carbon-to-nitrogen (C/N) were 20/1 - 44/1, the cellular assimilation of nitrogen (N/B) were 17.6 - 37.1 mg/g for heterotrophic cultivation; and C/N were 18/1 - 44/1, N/B were 17.6 - 43.3 mg/g for mixotrophic cultivation of C. pyrenoidosa with initial 10 g/l glucose; while N/B were 17.6 - 75.0 mg/g for autotrophic cultivation. When the NO3--N concentration of Basal medium was 173.3 mg/l, the reduction on 44.0 % NO3--N amount was able to obtain the same biomass for heterotrophic and mixotrophic cultivation, meanwhile 173.3 mg/l was 2.3-fold higher than the maximum nitrogen concentration that C. pyrenoidosa absorbed for the autotrophic cultivation. When nitrogen concentration was in the range that Chlorella absorbed, chlorophyll (including a and b) content increased with more NO3--N concentration in the medium. Chlorophyll content did not increase if nitrogen concentration was above the maximum absorbed amounts. Phosphorus concentration in the range enough for Chlorella growth had no effect on the chlorophyll content.