| The biofuels are receiving considerable attention as a substitute for petro diesel.For microalgae,the cell density or biomass and lipid contents are key components for biodiesel production.This study was conducted to develop favorable culture conditions for Dunaliella salina to maximize its biomass and lipid accumulation.The effect of salinity(0.5 to 2.5 M NaCl)on the cell population,biochemical composition,and lipid output of Dunaliella salina was examined under a controlled environment for 21 days.Maximum growth(6.57 × 107 to 7.17 × 107cells mL-1)potentials were observed at 1.5 to 2 M NaCl.The photosynthetic pigments and carbohydrates also showed trends similar to growth.The maximum carotenoid level(5.16 mg L-1)was recorded at 2 M NaCl.Almost all physicochemical parameters increased with increases in salinity,biomass(1231.66± 1.26 mg L-1)and lipid content(248.33 mg L-1),as recorded at 2 M NaCl.Based on fluorescence intensity,the highest values(11.84×107 cells mL-1)of neutral lipids and total lipids(22.28%)were recorded at optimum salinity levels.The present study suggests that a high biomass and lipid accumulation of Dunaliella salina SA 134 could be obtained at the 2 M NaCl level.Dunaliella salina(Dunaliella salina)is a potential source of biochemical compounds and subsequent lipids production for biodiesel.However lipid production from Dunaliella salina is dependent on biomass production rate and lipid content.To get more lipid as well as carotenoids production efficiency need to be improved.The aim of this study was to investigate different nitrogen sources with various concentration for improved microalgal growth and biochemical compounds production.In this study the culture was grown under three different nitrogen sources(NaNO3,NH4Cl and CO(NH2)2 concentrations(0.00025 M,0.1 M).The highest values(9.36 x 107 cells mL-1)at the time of harvest were found at 0.005 M NaNO3 fallowed by CO(NH2)2 and NH4Cl at 0.0005(8.33 and 6.48 × 107 cells mL-1)respectively.The result showed that maximum lipid contents(223.33,mg L-1)was obtained NaNO3 fallowed by CO(NH2)2 and NH4Cl(135 and 110 mg L-1)respectively.Total lipids on dry cell weight basis(27.61)was obtained by NaNO3,in the culture grown under low nitrogen concentration fallowed by urea and NH4Cl(21.43 and 14.46%).Whereas increase in N concentration up to certain level significantly increase in biomass production in all tested sources and the maximum biomass(1081.70 mg L-1)was obtained at 0.005 M NaNO3 compare to urea and NH4Cl(785 and 665).Carbohydrates and NL shows similar trend to total lipids.From the above results conclude that this strain could be cultivated for the high biomass production by using NaNO3 as a sole nitrogen source.The physiological factors for microalgae cultivation are the preliminary steps to overcome the potential biomass demand.In this regard,the influence of light intensity,(0,42,84,127 and 170 ?mol m-2 s-1)on the growth and biochemical composition of Dunaliella salina was matched in batch culture up to 21 d.The maximum cell growth 11.78×107 cell mL-1 and total lipids on dry cell weight basis(30%)were recorded at 127 ?mol m-2 s-1,at stationary phase of the experiment,The maximum fluorescence intensity,261.5×107 cells mL-1,was recorded at T4 on(127?mol m-2 s-1)while,minimun at low level,T1107 cells mL-1,was recorded at T4 on(127 ?mol m-2 s-1 while,minimum at low level,T172.175 × 107 cells.Further increased in fluorescence adversely effect on growth and lipids 72.175×107 ells.Furtner increased in fluorescence adversely effect on growth and lipids assembly of tested strain of Dunaliella salina.Photosynthesis pigments,chl a,chl b and carotenoids gradually increased with increase in time and light intensity as showed in(Figure 5.2 a,b and c).The maximum beta-carotene production 4.050 mgL-1 were recorded at high light(170 ?mol m-2 s-1)as compare to no light 1.170 mgL-1,Figure.5.2 c.Chlorophyll a and b has alike trend to carotenoids figure 5.2 a and b.carbohydrates were maximum at high light intensity at the time when Dunaliella salina cells entered to stationary phase of the growth figure 5.3 a and b.Development of lipid assembly is essential to improve the commercial feasibility of microalgal biodiesel production.An oleaginous microalgal strain,Dunaliella salina SA 134 was estimated for its potential as a biodiesel feed stock in this study.The combined effect of organic and in organic nutrient(NaHCO3,CH3COONa and C3H8O3)stresses on the lipid and other biochemical compounds productivity of the selected strain was studied.Maximum growth rate 8.26 × 107 cells mL-1 was observed by using glycerol with(0.01M)concentration fallowed by sodium bicarbonate,(0.1M)and sodium acetate(0.01M)7.41 ×107,6.13 × 107 cells mL-1 respectively.The highest lipid content of 826.67 mgL-1 and lipid productivity on dry cell weight basis 27.729%was obtained under nutrient stress with organic carbon source up to a specific concentration similar trend was observed in photo synthetic pigments.Results of carbohydrates stated that the extracellular carbohydrates production of Dunaliella salina relied on carbon sources as well as concentration and it was maximum(457.36 mg L-1)by using the glycerol as a sole carbon source as compare to sodium bicarbonate and sodium acetate(311.09 and 289.07 mg L-1)respectively.Neutral lipids assembly by Nile red fluorescennce 603.51 × 107 cells,was respectively.Neutral lipids assembly by Nile red fluorescence 603.51 ×107 cells,was recorded by using the organic carbon at very initial concentration at the end of the experiment fallowed by 541.12 × 107,425.91 ×107 cells mL-1,sodium acetate and sodium bicarbonate.Meanwhile,further increment of nutrients showed almost the negative trend on overall tested parameters. |
PDF Full Text Request