In connection with the cultivation of microalgae, the type of photobioreactors is one of the major parameters that should be considered as it directly affects the economy and efficiency of the process. In this study, a new design and fabrication of a microalgae culture photobioreactor using a plastic bag were performed. The performance of the photobioreactor was enhanced, and technically evaluated through tests such as stability, physical strength, light penetration rate, mass transfer rate, temperature control and mixing. The experimental results on plastic photobioreactors indicated that the main issues were related to the aeration and mixing in the system. To address this problem, an airlift pump was designed and installed at the end of the photobioreactor. The performance of the photobioreactor in the production of microalgae biomass was tested using the municipal effluent of Malek Ashtar University as a culture medium and inoculation of Chlorella vulgaris species. To optimize the culture conditions of microalgae, three factors: urea, phosphate, and baking soda concentrations were considered. The results showed the relationship between carbon, nitrogen, and phosphorus sources in increasing the cellular content of microalgae, which in the minimum amount of organic carbon source, with increasing the concentration of nitrogen and phosphorus, cell biomass production increases significantly. Accordingly, the production of more than 14 g/l of biomass in the amount of 0.9 g/l of baking soda, 0.25 g/l of urea, and 0.5 g/l of phosphate was obtained..

The aim of this study was to determine and optimize culture media for Chlorella vulgaris microalgae under mixotrophic conditions using waste molasses as a cheap carbon source containing both organic carbons and other nutrients. In the current study, at first the growth and lipid productivity of Chlorella vulgaris were assessed in different culture media and the best media was selected for mixotrophic growth conditions. Significant medium ingredients were screened through Plackett–Burman design. Then ingredients with positive effect were considered as a mixture component and their combinations were evaluated on lipid productivity using mixture design. According to results, Zarrouk medium was considered as the base medium with the highest biomass and lipid productivity of 72 and 7.1 mg/l.d , respectively. Based on the Plackett–Burman design, out of eleven factors, molasses, NaNO3 and K2HPO4 demonstrated key roles in biomass and lipid productivity in mixotrophic conditions. Consequently, the selected three factors were investigated by mixture design. The results showed that high concentration of molasses causes decrease in biomass and lipid productivity due to high turbidity and a blend consisting of approximately 9.5 g/l molasses, 5 g/l NaNO3 and 0.15 g/l K2HPO4 was found as the optimum mixture with obtained lipid productivity of 115 mg/l.d. In conclusion, waste molasses can be used as a promising feedstock for cost effective cultivation of C. vulgaris.

Microalgae have emerged as one of the most promising options for biodiesel production over the past few decades. Lipid extraction from microalgae for biodiesel production as a bottleneck of biodiesel production technology was the main purpose of this study. In this study different methods of the cell wall disruption were compared. Then, two methods of ultrasound and bead mill were used as methods of the cell wall disruption. The maximum lipid extracted by ultrasound was 17.10% and by bead mill was 15.16% (based on microalgae biomass dry weight). After the cell wall disruption of microalgae, for lipid extraction, chloroform-methanol solvent combination was used as a high extraction method and hexane-ethanol solvent combination was used as an environmentally friendly method. In this regard, the effect of solvent to biomass ratio, temperature and extraction time was investigated and the optimal results for chloroform-methanol solvent combination were 8 ml/g, 45°C and 60 minutes, respectively, and for hexane-ethanol combination were 6 ml/g, 35◦C and 73 minutes, respectively. Under these optimal conditions, the highest amount of extracted lipid from Chlorella vulgaris with a moisture content of 87.50%, and ultrasound as a cell wall disruption method were obtained 20.39% and 16.41% (based on microalgae dry weight) with a combination of chloroform-methanol solvents and hexane-ethanol respectively. Also the highest extraction rates of 17.63% and 13.85% were obtained for the combination of chloroform-methanol and hexane-ethanol solvents, respectively by bead milling as cell wall disruption method