An Optimal Method for Biomass Measurement of Microalgae

Key words: 
• Growth monitoring /
• optical density /
• cell count /
• dry weight

Abstract: Five microalgae species,i. e. Desmodesmus sp. WC08,Chlorella sp. C74,Monoraphidium sp. C29,Micractinium sp. C67 and Chlorella sp. QH were batch cultured under photo-autotrophy with blue-green（ BG-11） medium as a basic medium,and their biomasses were measured during their growth. The microalgae cultures were gradient diluted to determine their optical density（ OD）,cell density（ CD） and dry weight（ DW）,with which mathematical relations with the biomass of the microalgae were established. At the maximum absorption wavelength of 680 nm,the CD and the OD of the microalgae at the exponential growth stage had a linear relation,which was,expressed as y = 0. 336 66x-0. 002 88,R²= 0. 998 7; the DW was linearly related with the OD in a linear equation of y = 1. 095 98x-0. 064 04,R²= 0. 973 14. The difference between the OD and the CD using Desmodesmus sp. WC08 on five different mediums and the difference of five different microalgae species cultured on the same medium between the OD and the CD were compared and analyze. The results showed that the OD was the best index for calculating of biomass,dry weight and cell density of the microalgae. The OD determination is hence the best method for biomass measurement of the microalgae during the culture.