2.4. Determination of cell growth and CO2 fixation rate
Microalgae biomass concentration was determined by measur-
ing the optical density of the sample at a wavelength of 680 nm
(denoted as OD680) using a UV/Vis spectrophotometer (model U-
2001, Hitachi, Tokyo, Japan) after proper dilution with deionized
water. The OD680 values were converted to biomass concentration
via appropriate calibration between OD680 and dry cell weight:
Biomass ðg=LÞ ¼ 0:584 OD680 2:367 R2 ¼ 0:99 -
The specific growth rate of microalgal culture was obtained by
following calculation:
lðd1
Þ ¼ d ln X
dt j
max ði:e: maximum slope from lnX versus t plotÞ
where X and t indicate the biomass concentration (g/L) and cultiva-
tion time (day), respectively.
The biomass productivity (Pbiomass) during the culture period
was calculated from the equation:
Pbiomass ðg DCW=L=dÞ ¼ DX
Dt
where DX is the variation of biomass concentration (g DCW/L)
within a cultivation time of Dt (d).