Growth and biochemical composition of marine microalga Nannochloropsis oceanica, cultured under nutrient limitation on reduced cost media, for

aquaculture and biodiesel production. M. Ashour* and Abdel-Wahab Kamil

*Corresponding Author: Dr. Mohamed Ashour; Email: microalgae_egypt@yahoo.com; Cell: +201283184088

1. ABSTRACT Comparing to N/P ratio of F/2 Guillard medium, six treatments of N/P

ratios (1.6, 3.2, 4.8, 9.6, 10.3, and 20.7) were prepared from nitric acid (NU) or ammonium sulphate (NH), as a nitrogen source, with phosphoric acid (P) as phosphorus source.

The results investigated that some CAGF media achieved significant (P≤0.05) growth and biochemical composition higher than F/2, depending on N/P ratios and atomic sources concentrations.

2. INTRODUCTION Microalgae culture media should be economical, allow for high growth,

satisfy the needs of microalgal cells, and easy to prepare. In this study, we evaluate the effect of different medium formula

prepared from commercial agricultural fertilizers (CAGF), comparing to F/2 Guillard medium as control medium, on growth (cell density, CD; dry weight, DW and specific growth rate, µ) and biochemical composition (lipid, protein, and carbohydrate) of Nannochloropsis oceanica.

3. MATERIAL AND METHODS 3.1. Experimental Conditions and Design

5. CONCLUSION 1. Different nitrogen sources may affect the growth and biochemical composition of N. oceanica, depending on the atom concentrations and N/P ratios. 2. Although there were no significant differences in N. oceanica dry weights between treatments, significant differences in biochemical compositions were achieved 3. Depending on the N and P atom concentrations and N/P ratios, the two commercial media, comparing to F/2 standard Guillard medium, achieved the highest

growth (cell density, dry weight and specific growth rate) and biochemical composition (lipid, protein and carbohydrate), with the advantage of low production cost (1/40 of production cost of F/2 standard Guillard medium).

All treatments were conducted without aeration in conical flasks 250 ml filled with 100 ml of culture medium under controlled conditions of temperature (21±1 ºC), salinity (35ppt), and continuous illumination (1000 Lux /24h). The samples for growth parameters and biochemical analysis were taken at late exponential phase (three replicates for each treatment). All experiments were ended when the growth rate had reached to the death phase.

Composition and preparing cost of F/2 standard Guillard medium and other CAGF media are presented in Table 2. In addition to nitrogen and phosphorus sources, vitamin B12 were added in the concentration of 100 µg/l and 1000 µg/l, respectively (in form of local human pharmacy ampoules, commercially named Tri-B, produced by The Nile Co. for Pharmaceuticals and Chemical Industries, Cairo, Egypt). No trace minerals were added with CAGF media.

3.2. Tested Parameters 3.2.1. Growth Parameters: The growth was assessed by determination of algal dry weight (DW), cell density (CD) and specific growth rate (µ). 3.2.2. Biochemical Constituent Analysis: 10 ml of N. oceanica culture were taken at late exponential phase (three replicates for each analysis), centrifuged (3000 rpm/10 min) and the pellets were preserved in-20°C until analysis. Total lipids (Bligh and Dyer, 1959), total proteins (Hartree 1972), and total carbohydrates (Dubois et. al., (1956) were determined.

Comparing to nitrogen and phosphorus molar concentrations of F/2 Guillard medium; 6 different nutrient media formulas were conducted from nitric acid (NU) or ammonium sulphate (NH), as a nitrogen source, with phosphoric acid (P) as phosphorus source. The ratios and concentrations of NU, NH and P are presented in Table 1.

N (g/l) P (ml/l)

F/2 Control 0.0124 0.0013 9.6

NU100+P100 0.0124 0.0013 9.6

NU50+P50 0.0062 0.0006 10.3

NU50+P100 0.0062 0.0013 4.8

NU50+P300 0.0062 0.0039 1.6

NU100+P50 0.0124 0.0006 20.7

NU100+P300 0.0124 0.0039 3.2

NH100+P100 0.0124 0.0013 9.6

NH50+P50 0.0062 0.0006 10.3

NH50+P100 0.0062 0.0013 4.8

NH50+P300 0.0062 0.0039 1.6

NH100+P50 0.0124 0.0006 20.7

NH100+P300 0.0124 0.0039 3.2

Molar conc. Of N/P

RatioAbbriv.

Table 1: The ratios and concentrations of NU and NH

4. RESULTS

Figure 1: Effect of F/2 control medium, comparing to the two commercial media consist of different molar concentration of nitric acid, NH or ammonium sulphate, NH (nitrogen-based-media) with phosphoric acid (phosphorus- based-media) on cell density (a), dry weight (b), specific growth rate (c), lipid (d), protein (e) and carbohydrate (f) of N. oceanica

a b

c d

e f

Table 2: Chemical composition and production cost of 1000 L of F/2 Guillard medium, comparing to the two experimented commercial media

Vitamin B1 and B12 were added in form of Egyptian local human pharmacy ampoules, commercially named Tri-B, produced by The Nile Co. for Pharmaceuticals and Chemical Industries, Cairo, Egypt. No trace minerals were added with commercial media

The 2016 Algae Biomass Summit, October 23-26, 2016, Phoenix , Arizona