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Bio-Hydrocarbons from Algae -
Impacts of temperature, light and salinity on algae growthby Jian Qin
February 2005
RIRDC Publication No 05/025 RIRDC Project No SQC-1A
Five Botryococcus strains have been obtained from China, Japan and UK. So far, the research has focused on the physical requirement of B. braunii (China strain 1) under intensive culture. We have identified the tolerance range of environmental factors including photoperiod, temperature, light intensity, and salinity and determined the relationship between oil content in the algae and culture conditions.
Firstly, we developed the methods for measuring algal growth and lipid content. Nile red staining was used for lipid measurement, while optical density was used to measure the abundance of B. braunii in a spectrophotometer.
Secondly, the photoperiod of 12 h light : 12 h dark was considered the optimum light regime to sustain algal growth. Based on this, temperature, light intensity and salinity experiments were conducted successively. The optimal temperature for China strain 1 was 23 °C under which the algae gained maximum biomass and lipid production. The temperature tolerance was between 20 and 30°C. The suitable range of light intensity for China strain 1 was between 30 and 60 W/m2.
Finally, six concentrations of NaCl medium (0, 0.15, 0.25, 0.35, 0.5 and 0.7 M) were prepared to examine the salinity tolerance of the algae (0.1 M NaCl = 5.85‰). Algae in 0.15 M NaCl produced maximum biomass and lipid content. The generation time of algal cells was about 2 days. It is possible to culture B. braunii in brackish waters in Australia. This is a significant result given the limited availability of freshwater in Australia.
To obtain the maximum biomass and hydrocarbon production in China strain 1, the optimal culture conditions are (1) temperature: 23 °C, (2) light intensity: 30~60 W/m2 irradiance, (3) photoperiod: 12 h light and 12 h dark, and (4) salinity: 8.775 ‰ medium.
Considering the variation of different Botryococcus strains, it will be necessary to select high yielding and commercially viable strains in future to supplement the requirements of energy supply in Australia.
 
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