Growth comparison of Arthrospira platensis in different vessels: standard cylinder vs. enhanced surface area at low light

Figures & data

Figure 1. Representation of the cross sections of the two flasks. The control flask (a) on the left, and the prototype flask (b) on the right have identical cross-sectional areas, but the sidewall configuration of the two flasks is different. These diagrams are intended for illustrative purposes only. They are not presented to scale, nor are they intended for manufacturing or engineering purposes. The key geometric measures of the respective flasks are presented in Table 1.

Table 1. Key Geometric Measures of the Flasks.

Geometric Measure	Control	AlgaTube^™	Units
Capacity Volume^a	1441	1441	ml
Photon Surface Area^b	743	1641	cm^2
Relative Photon Surface Area^c	100%	220%	% of control
Cross Section Surface Area^d	47	47	cm^2
PSA Vol^−1 Ratio^e	0.52	1.13	cm^−1
Relative PSA Vol^−1 Ratio^f	100%	220%	% of control

^aCapacity Volume: total volume of the flask when full to brim (ml = cm³).

^bPhoton Surface Area: total surface area of the sidewalls of the flask (cm²).

^acRelative Photon Surface Area: expressed as %, with control = 100%.

^dCross Section Surface Area: area across which gas exchange and evaporation occur (cm²).

^ePSA Vol⁻¹ Ratio: ratio of PSA to Volume for each flask (cm²/cm³ = cm⁻¹).

^fRelative PSA Vol⁻¹ Ratio: expressed as % with control = 100%.

Figure 2. Configuration of the growth chamber. The control flask was on the left, and the prototype flask was on the right. The two light panels were affixed to the rear wall of the incubator. The incandescent light was attached to the door and centered. The magnets can be seen on the lower left side of the control flask and on the lower right side of the prototype flask. The picture was taken with the door open for convenience.

Table 2. Dilutions for % Transmittance vs. Concentration standard curve.

Dilution #	Dilution Rate (%)	Concentration (g l^–1)	%T	ABS
Stock	100	1.63	0.70	>2.02
1	61	1.00	0.90	>2.02
2	55	0.90	0.95	2.02
3	49	0.80	1.00	2.00
4	43	0.70	1.20	1.95
5	33	0.60	1.99	1.80
6	31	0.50	3.10	1.52
7	25	0.40	5.70	1.30
8	18	0.30	10.50	0.98
9	12	0.20	23.50	0.64
10	6	0.10	47.50	0.33
11	3	0.05	69.50	0.16
12	1	0.02	85.50	0.07

Figure 3. Standard Curve. This chart plots the data from the dilution table to illustrate the standard curve used to determine daily culture concentration from OD₅₉₀ readings.

Figure 4. (A) and 4(B). Daily Concentration and Cumulative Production values of prototype and control tubes. 4(a) Chart plotting the daily Concentration (C_d), averaged across the four independent replicates, for the AlgaTube™ prototype and cylindrical control, respectively. The prototype data points are represented by solid lines and black triangles (━▲━). Δ_C10 = +34% (p = 0.02, Wilcoxon Rank Sum Test). 4(b) Chart plotting the daily Cumulative Production (CP_d), averaged across the four independent replicates, for the two vessels, AlgaTube™ prototype and cylindrical control, respectively. δ_cp10 = +41% (p = 0.02, Wilcoxon Rank Sum Test). In both 4(a) and 4(b), the prototype data points are represented by solid lines and black triangles (━▲━). The control data points are represented by dashed lines and black circles (—□—).

Figure 5. Time-Parsed Mean Daily Production. The Mean Daily Production (MDP) data were, themselves, averaged together longitudinally, for each of three different time periods within the 10-day experiment. The respective Delta (∆_mdp) values and p-values for different time periods are shown. The mean culture concentration during each of those time periods is shown below the x axis labels. The bars representing the control flask are white, and the bars representing the prototype flask are shaded grey.

Table 3. Quantification of primary differences between present study vs. da Silva et al. (2016).

Variable Name	Value in Present Study	Value in da Silva et al. (2016)	Delta (Δ)^b
Initial Concentration [g l^−1]	0.25	0.40	+60%
Light Intensity [μmol photons m^−2 s^−1]	55	100	+82%
PSA Vol^−1 Ratio [cm^−1]	1.13	1.94	+72%
Total Delta (Δ)			+214%
Maximum Concentration^a [g l^−1]	1.90	8.44	+344%

^aIn the present study, C_max was on Day #10. In da Silva et al. (2016), C_max was on Day #9.

^abA positive Δ means da Silva et al. (2016) was higher than the present study.

Table 4. Ranked summary of all differences between present study vs. da Silva et al. (2016).

Variable Name	Value in Present Study	Value in da Silva et al. (2016)	Delta (��)^b
Mixing Technique	Air Bubbles	Continuous Circulation	+83%
Light Intensity (µmol photons m-2 s-1)	55	100	+82%
PSA Vol^−1 Ratio (cm^−1)	1.13	1.94	+72%
Initial Concentration (g l^−1)	0.25	0.40	+60%
Light Quality	LED Mix	Cool White Fluorescent	+30%
Vessel Material	3-D Printing Resin	Glass	+10%
Extra Hardware	Hose Clamps	n/a	+7%
Total Delta			+344%
Cmax^a (g l^−1)	1.90	8.44	+344%

^aIn the present study, C_max was on Day #10. In da Silva et al. (2016), C_max was on Day #9.

^abA positive Δ means values in da Silva et al. (2016) was higher than the present study.

Table 5. Summary of key metrics.

Key Metric	Control	AlgaTube™	Delta (Δ)^a	p-value
Maximum Concentration (g l^−1)	1.42	1.90	+34%	0.02
Total Cumulative Production (g l^−1)	1.17	1.65	+41%	0.02
Specific Growth Rate (day^−1)	0.17	0.20	+17%	0.02
Maximum Specific Growth Rate (day^−10)	0.40	0.49	+23%	0.02
Mean Daily Production (g l^−1)	0.12	0.17	+41%	0.001
Maximum Daily Production (g l^−1)	0.21	0.29	+38%	0.19

^aPositive values for Delta indicate that the AlgaTube^TM was higher than the control.

da Silva, M. F., Casazza, A. A., Ferrari, P. F., Perego, P., Bezerra, R. P., Converti, A., & Porto, A. L. F. (2016). A new bioenergetic and thermodynamic approach to batch photoautotrophic growth of Arthrospira (Spirulina) platensis in different photobioreactors and under different light conditions. Bioresources Technology, 207, 220–228.

 Google Scholar