Measurement of the cell density of microalgae by an optical method

Abstract Microalgae are currently interesting in industry because it can generate many useful products, such as supplementary food, cosmetic and biomass energy. During the cultivation, the growth of microalgae is traditionally followed by cell counting with an optical microscope and a calculation of the cell density. To obtain a precise value of the cell density, the measurement should be performed by ones with good laboratory skills and it takes a long time. We develop a photometer to determine the cell density of microalgae. The photometer consists of a light dependent resistor as the sensor, a light emitting diode as the light source, and a microcontroller which controls all components as well as the cell density calculation using a calibration equation. To test the performance of our device, we cultivate marine microalgae Dunaliella Salina with different aerations and measure the cell density during 18-day cultivation period by using the photometer and the cell counting with an optical microscope. The results show that the cell density values obtained from both measurement methods increase with day of cultivation in a similar manner. Thus, the photometer is a good alternative device to follow the growth of microalgae. Furthermore, it is relatively inexpensive, quick and easy for the operator to use.