The Effect of Salinity on Growth, Dry Weight and Lipid Content of the Mixed Microalgae Culture Isolated from Glagah as Biodiesel Substrate

Abstract

Microalgae use photosynthesis to convert solar energy into chemical energy, such as lipid and they can be a replacement for oil-based fuels. They are among the fastest growing plants in the world, and about 50% of their weight is oil. This lipid oil can be used to make biodiesel. Unfortunately, there are only some of potential strains isolated from Indonesia and most of the biodiesel productions are usually using a single strain. Then, although they are rich of oils, their biomass productivity is still low. Salinity treatment can be used to increase their biomass as well as their lipid content. Therefore, the research aim was to study the effect of salinity on the growth, dry weight and lipid content of mixed microalgae isolated from Glagah, Yogyakarta. The mixed microalgae were cultured in 3NBBM medium with different salinities or types of water (sea water, brackish water, and fresh water). The cultures were incubated at light intensity 3,000 lux under dark:light exposure of 12:12 h for 7 days. The number of cells was counted every 24 h with a Haemocytometer, and the biomass was calculated based on the dry weight. The lipid content was measured on days 0, 3, and 7 using NR (Nile Red) staining, and then the amount of lipid was analyzed using a fluorescence microscope and measured with CellProfiler 2.0 software. The highest dry weight and lipid content were found in seawater medium, they accounted for 3.42 mg/mL and 13.58% at day 7, respectively. Whereas, the highest number of cells was found in freshwater medium, this was 9.8 × 10 6 cells/mL.