| Microalgae are being researched for its potential as an attractive biofuel feedstock, particularly for their lipid production. For maximizing the biofuel production, it is necessary to explore the effects of exogenous substances and cultivation strategies on algae. In this study, the effects of nitrogen (N) sources, carbon to nitrogen ratios, metal ions, cultivation strategies and carbon dioxide concentrationon algal growth, lipid-producing potential and in-depeth water purifying capability of Chlorella sp. HQ were investigated.The study to investigate the effects of nitrogen sources (NO2-N, NO3-N, urea-N, NH4-N and N-deficiency) and C/N ratios(C/N=0,1.0,3.0 and 5.0) on synchronous water purification and lipid production of Chlorella showed that the combination of NO2-N treatment under C/N=1.0 is the best combination of Chlorella sp. HQ for its further application of this coupling technique (NO2-N removal: 91.22±1.38%; TP removal:91.83±0.09%; TAG productivity:0.64±0.10 mg·L-1·d-1). The results indicated that Chlorella sp. HQ might be considered as a new candidate for further application of the coupling technique of microalgae-based biofuel production and wastewater purification.The effects of metal ions(Cr6+, Cu2+, Mn2+, Zn2+, Fe3+, Na+and K+) on algae lipid production combined with water purification showed that Chlorella sp. HQ had strong resistance to metal ions and could efficiently remove metal ions, nitrogen and phosphorus(Fe3+:85.40～98.73%; Mn2+:45.63-97.24%; Zn2+:81.93-100.00%; Cu2+:81.71-95.19%; Cr6+:45.60%; TN:78.15-94.77%; TP:80.52-100%) and achive a high TAG yield(33.39±19.42 mg·L-1,31.9 mgK+·L-1). The lipid/TAG content significantly increased up to 32.56-100% and 37.53-100% with the addition of metal ions. Therefore, the metal ions in the culture condition might influence algal lipid accumulation and in-depth wastewater purification properties.The research on different cultivation strategies (autotrophic cultivation, heterotrophic cultivation,7 d heterotrophic+5 d mixotrophic two-stage cultivation,7 d heterotrophic+ 5 d autotrophic two-stage cultivation, fed-batch culture and semi-continuous culture) and CO2 concentration (0,3,9,16 and 23%) in a photobioreactor found that Chlorella sp. HQ showed a great TN and TP removal potential (TN: 93.72-95.82%; TP:92.73-100%) under different cultivation strategies. Among them, heterotrophic cultivation was the best cultivation strategy for algal lipid production potential of Chlorella sp. HQ to achieve the highest TAG productivity 3.38 mg·L-1·d-1, the condition which had the merit for biofuel production. And 9%(v/v) CO2 increased total lipid content of heterotrophic culture condition by 3.74-191.11% in comparison with other CO2 concentration (0,3,16,23%). The microalga could bioremediate total organic carbon (TOC), TN and TP efficiently from the wastewater to the extent of 43.98-93.89%,100% and 89.50-92.01%, respectively. In sum, the combination of 9%(v/v) CO2 and heterotrophic culture condition was the most suitable culture condition for algal biofuel production and wastewater purification synchronously. |
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