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The difference in effective light penetration may explain the superiority in photosynthetic efficiency of attached cultivation over the conventional open pond for microalgae.

Wang J, Liu J, Liu T - Biotechnol Biofuels (2015)

Bottom Line: In this research, the growth, photosynthetic oxygen evolution, and specific growth rate for microalgal cells in both open-pond and attached cultivation were studied to determine the effective light penetration at different phases of the cultivation.As the biomass concentration increased from day 4 to day 10, the light could only effectively penetrate 45.5% of the open-pond depth, and then effective light penetration gradually decreased to 31.1% at day 31, when the biomass density reached a maximum value of 0.45 g L(-1) or 90 g m(-2).Higher light penetration efficiency might be the reason why, using attached cultivation, observed values for photosynthetic efficiency were higher than those recorded in conventional open-pond suspended cultures.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong 266101 People's Republic of China.

ABSTRACT

Background: The 'attached cultivation' technique for microalgae production, combining the immobilized biofilm technology with proper light dilution strategies, has shown improved biomass production and photosynthetic efficiency over conventional open-pond suspended cultures. However, how light is transferred and distributed inside the biofilm has not been clearly defined yet.

Results: In this research, the growth, photosynthetic oxygen evolution, and specific growth rate for microalgal cells in both open-pond and attached cultivation were studied to determine the effective light penetration at different phases of the cultivation. As a result, the light conditions inside the culture broth as well as the biofilm were revealed for the first time. Results showed that outdoor, in a conventional 20-cm deep open pond, all of the algal cells were fully illuminated in the first 3 days of cultivation. As the biomass concentration increased from day 4 to day 10, the light could only effectively penetrate 45.5% of the open-pond depth, and then effective light penetration gradually decreased to 31.1% at day 31, when the biomass density reached a maximum value of 0.45 g L(-1) or 90 g m(-2). In the attached cultivation system, under nitrogen-replete condition, almost 100% of the immobilized algal cells inside the biofilm were effectively illuminated from day 0 through day 10 when the biomass density increased from 8.8 g m(-2) to 107.6 g m(-2).

Conclusion: Higher light penetration efficiency might be the reason why, using attached cultivation, observed values for photosynthetic efficiency were higher than those recorded in conventional open-pond suspended cultures.

No MeSH data available.


Related in: MedlinePlus

The schematic flow chart of the experiment design to determine the effective illumination depth for the attached cultivation.
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Fig8: The schematic flow chart of the experiment design to determine the effective illumination depth for the attached cultivation.

Mentions: The dE for the algal biofilm of the attached cultivation and conventional aqueous suspended open pond were determined under indoor and outdoor conditions, respectively. For the attached cultivation, the dE was measured with a single-layer attached cultivation system (Figure 1B) following the flow chart of Figure 8. Firstly, the algal cells were attached cultivated for 10 days with BG-11 (step 1; refer to the ‘Cultivation systems’ section for details). Every other day, some of the algal disks were sampled and the attached cells on it were detached and washed three times with de-ionized water (step 2). A ‘marker’ layer was built by filtering some fresh inoculum onto new cellulose acetate/nitrate membranes at the biomass density of s (g m−2). Then, some aliquots of the re-suspended algal culture from step 2 were gently filtered onto the ‘marker’ layers to form ‘double-layer’ attached algal disks. The corresponding ‘single-layer’ attached algal ‘disks’ were also prepared at the same time as a control using identical aliquots of re-suspended algal culture but without the ‘marker’ layer (step 3). Both of the newly prepared ‘double-layer’ and ‘single-layer’ algal disks were cultivated for 24 h under the same environmental conditions using the PBR depicted in Figure 1B. The biomass increase for the ‘double-layer’ algal disk was denoted by a (g m−2) and the biomass increase for the corresponding ‘single-layer’ algal disk was a’ (g m−2), so that the net biomass gain for the ‘marker’ layer was calculated as δ = a − a’ (g m−2), and μ was calculated as:Figure 8


The difference in effective light penetration may explain the superiority in photosynthetic efficiency of attached cultivation over the conventional open pond for microalgae.

Wang J, Liu J, Liu T - Biotechnol Biofuels (2015)

The schematic flow chart of the experiment design to determine the effective illumination depth for the attached cultivation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4389658&req=5

Fig8: The schematic flow chart of the experiment design to determine the effective illumination depth for the attached cultivation.
Mentions: The dE for the algal biofilm of the attached cultivation and conventional aqueous suspended open pond were determined under indoor and outdoor conditions, respectively. For the attached cultivation, the dE was measured with a single-layer attached cultivation system (Figure 1B) following the flow chart of Figure 8. Firstly, the algal cells were attached cultivated for 10 days with BG-11 (step 1; refer to the ‘Cultivation systems’ section for details). Every other day, some of the algal disks were sampled and the attached cells on it were detached and washed three times with de-ionized water (step 2). A ‘marker’ layer was built by filtering some fresh inoculum onto new cellulose acetate/nitrate membranes at the biomass density of s (g m−2). Then, some aliquots of the re-suspended algal culture from step 2 were gently filtered onto the ‘marker’ layers to form ‘double-layer’ attached algal disks. The corresponding ‘single-layer’ attached algal ‘disks’ were also prepared at the same time as a control using identical aliquots of re-suspended algal culture but without the ‘marker’ layer (step 3). Both of the newly prepared ‘double-layer’ and ‘single-layer’ algal disks were cultivated for 24 h under the same environmental conditions using the PBR depicted in Figure 1B. The biomass increase for the ‘double-layer’ algal disk was denoted by a (g m−2) and the biomass increase for the corresponding ‘single-layer’ algal disk was a’ (g m−2), so that the net biomass gain for the ‘marker’ layer was calculated as δ = a − a’ (g m−2), and μ was calculated as:Figure 8

Bottom Line: In this research, the growth, photosynthetic oxygen evolution, and specific growth rate for microalgal cells in both open-pond and attached cultivation were studied to determine the effective light penetration at different phases of the cultivation.As the biomass concentration increased from day 4 to day 10, the light could only effectively penetrate 45.5% of the open-pond depth, and then effective light penetration gradually decreased to 31.1% at day 31, when the biomass density reached a maximum value of 0.45 g L(-1) or 90 g m(-2).Higher light penetration efficiency might be the reason why, using attached cultivation, observed values for photosynthetic efficiency were higher than those recorded in conventional open-pond suspended cultures.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, Shandong 266101 People's Republic of China.

ABSTRACT

Background: The 'attached cultivation' technique for microalgae production, combining the immobilized biofilm technology with proper light dilution strategies, has shown improved biomass production and photosynthetic efficiency over conventional open-pond suspended cultures. However, how light is transferred and distributed inside the biofilm has not been clearly defined yet.

Results: In this research, the growth, photosynthetic oxygen evolution, and specific growth rate for microalgal cells in both open-pond and attached cultivation were studied to determine the effective light penetration at different phases of the cultivation. As a result, the light conditions inside the culture broth as well as the biofilm were revealed for the first time. Results showed that outdoor, in a conventional 20-cm deep open pond, all of the algal cells were fully illuminated in the first 3 days of cultivation. As the biomass concentration increased from day 4 to day 10, the light could only effectively penetrate 45.5% of the open-pond depth, and then effective light penetration gradually decreased to 31.1% at day 31, when the biomass density reached a maximum value of 0.45 g L(-1) or 90 g m(-2). In the attached cultivation system, under nitrogen-replete condition, almost 100% of the immobilized algal cells inside the biofilm were effectively illuminated from day 0 through day 10 when the biomass density increased from 8.8 g m(-2) to 107.6 g m(-2).

Conclusion: Higher light penetration efficiency might be the reason why, using attached cultivation, observed values for photosynthetic efficiency were higher than those recorded in conventional open-pond suspended cultures.

No MeSH data available.


Related in: MedlinePlus