Cultivation of Nannochloropsis sp. using narrow beam angle light emitting diode in an internally illuminated photobioreactor

摘要

Background: This paper reports on the growth condition of Nannochloropsis sp. in an annular column-type photo-bioreactor (PBR) using light-emitting diode as an internal illumination. Methods: The microalgae growth in the 20-L batch culture mode under mixed blue (450 nm) and red (660 nm) light-emitting diode (LED) in various conditions such as photoperiod and light intensity (controlled by supplied current) was monitored. Compact-type 5-W LED module with narrow beam angle (radiation pattern) was installed in the PBR so as to obtain higher intensity and deeper penetration to the culture. Results: Based on the PBR dimension with optical path length 120 mm, the minimum light intensity required at the PBR tank inner surface at initial stage of cultivation was approximately 350-370 mol m~(-2)s~(-1), while mean light intensity derived was 140-160 mol m~(-2)s~(-1). Photoperiod ratio of light:dark at 18:6 h provided better results compared to 12:12 in terms of final cell density achieved. Efficiency of light utilization was calculated to be 9.0 × 109 cell/mol photon (0.49 g/mol photon), while biomass volumetric productivity was 0.04 g L~(-1)day~(-1). Conclusion: The usage of narrow beam angle LED was feasible to be used but with further improvement is necessary.