GROWTH AND COMPOSITION OF <i>Arthrospira (Spirulina) platensis</i> IN A TUBULAR PHOTOBIOREACTOR USING AMMONIUM NITRATE AS THE NITROGEN SOURCE IN A FED-BATCH PROCESS

Cruz-Martínez, C.; Jesus, C. K. C.; Matsudo, M. C.; Danesi, E. D. G.; Sato, S.; Carvalho, J. C. M.

doi:10.1590/0104-6632.20150322s00003062

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BIOPROCESS ENGINEERING • Braz. J. Chem. Eng. 32 (2) • Apr-Jun 2015 • https://doi.org/10.1590/0104-6632.20150322s00003062 copy

GROWTH AND COMPOSITION OF Arthrospira (Spirulina) platensis IN A TUBULAR PHOTOBIOREACTOR USING AMMONIUM NITRATE AS THE NITROGEN SOURCE IN A FED-BATCH PROCESS

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

NH₄NO₃ simultaneously provides a readily assimilable nitrogen source (ammonia) and a reserve of nitrogen (nitrate), allowing for an increase in Arthrospira platensis biomass production while reducing the cost of the cultivation medium. In this study, a 2²plus star central composite experimental design combined with response surface methodology was employed to analyze the influence of light intensity (I) and the total amount of added NH₄NO₃ (M_t) on a bench-scale tubular photobioreactor for fed-batch cultures. The maximum cell concentration (X_m), cell productivity (P_X) and biomass yield on nitrogen (Y_X/N) were evaluated, as were the protein and lipid contents. Under optimized conditions (I = 148 μmol·photons·m^-2·s^-1 and M_t = 9.7 mM NH₄NO₃), X_m = 4710 ±34.4 mg·L^-1, P_X = 478.9 ±3.8 mg·L^-1·d^-1 and Y_X/N = 15.87 ±0.13 mg·mg^-1 were obtained. The best conditions for protein content in the biomass (63.2%) were not the same as those that maximized cell growth (I = 180 μmol·photons·m^-2·s^-1 and M_t = 22.5 mM NH₄NO₃). Based on these results, it is possible to conclude that ammonium nitrate is an interesting alternate nitrogen source for the cultivation of A. platensisin a fed-batch process and could be used for other photosynthetic microorganisms.

Keywords
Arthrospira (Spirulina) platensis; Fed-batch cultivation; Ammonium nitrate; Light intensity; Tubular photobioreactor

Test	X ₁ ^a a X1 = Codified values for light intensity,	X ₂ ^b b X2 = Codified values for addition of ammonium nitrate (Mt),	I^c c I = Light intensity values (μmol photons m-2s-1),	M _t ^d d Mt = total amount of ammonium nitrate added (mM),	T _C ^e e TC = Cultivation time (days),	X _m ^f f Xm = Maximum cell concentration (mg L-1),	P _X ^g g PX = Cell productivity (mg L-1d-1),	Y _X/N ^h h YX/N = Yield of biomass on nitrogen (mg mg-1),	NH₃ⁱ i NH3 = Final concentration of total ammonia (mM),	NO₃^j j NO3 = final concentration of nitrate (mM),	Lip ^k k Lip = lipid biomass content (%),	Ptn ^l l Ptn = protein biomass content (%),
Part A. Tests of the initial experimental design
1	-1	-1	60	7.5	8	3914	439.2	16.73	0.55	^* * value below the detection limit of the analytical method,	8.3	23.8
2	+1	-1	180	7.5	10	4834	443.4	21.11	0.02	0.4	5.9	14.8
3	-1	+ 1	60	22.5	5	1029	125.8	1.00	11.10	12.2	^ It was not possible to quantify (cell death).	^ It was not possible to quantify (cell death).
4	+1	+ 1	180	22.5	5	960	112.1	0.89	10.4	10.6	17.3	63.2
5	0	-1.414	120	4.4	7	3422	431.7	24.53	0.01	0.5	3.3	12.3
6	-1.414	0	35	15.0	7	2164	252.0	4.20	0.09	9.2	12.5	41.7
7	0	+ 1.414	120	25.6	4	676	69.1	0.38	10.2	12.2	^ It was not possible to quantify (cell death).	^ It was not possible to quantify (cell death).
8	+ 1.414	0	205	15.0	8	3926	440.7	8.39	0.44	0.63	8.1	25.8
9	0	0	120	15.0	8	4194	474.2	9.03	0.10	12.4	7.6	25.5
10	0	0	120	15.0	7	3854	493.4	8.22	0.10	11.3	7.0	22.5
11	0	0	120	15.0	8	3938	442.2	8.42	0.06	7.5	9.9	29.3
Part B. Confirmation tests
12	0.47	- 0.71	148	9.7	9	4699	477.7	15.83	0.07	0.5	10.3	21.4
13	0.47	- 0.71	148	9.7	9	4683	475.9	15.77	0.04	2.6	9.4	18.9
14	0.47	- 0.71	148	9.7	9	4749	483.2	16.01	0.03	1.2	10.5	19.8

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