Abstract

The growth parameters of all the three isolated Spirulina strains such as optical density, cell population, specific growth rate and doubling time of isolated Spirulina strains were studied in Zarrouk’s medium. A. The SpirulinaS1 strain showed highest growth in terms of optical density value at 560nm (1.870), cell population (5.30 CFU ml-1), specific growth rate (0.038 and doubling time (18.23) on 30th day. The effects of temperature, pH, light intensity and salinity on growth of Spirulina strains (S1, S2, and S3) and reference strain (CAS10) were determined in Zarrouk’s medium. The optimum temperature for the growth of all Spirulina strains was found to be 35°C followed by 40°C and 30°C. The highest biomass (0.308 mg ml-1) were recorded in Spirulina-S1 strain at 35°C.

1. Introduction

The generic name “single cell protein (SCP) was designed an international meeting held at MLT, USA to include protein source from unicellular or multicellular microbes like bacteria, yeast, fungi and algae. The concept of utilizing SCP is not completely new, as protein are already being used in foods and feeds in different regions of the world at varying levels ^{1, 4}.

The ideal microorganism should possess the following technological characteristics like high specific growth rate, biomass yield, low nutritional requirements, ability to develop high cell density, stability during multiplication, capacity for genetic modification and good tolerance to temperature and pH. In addition, it should have a balanced protein and lipid composition. It must have a low nucleic acid content, good digestibility and to be non-toxic. The dried cells of microorganisms such as bacteria, fungi, yeasts and algae that are grown in large-scale culture systems as proteins, for human or animal consumption are collectively known as single cell protein ³. Single cell protein are characterized by fast growth rate, high protein content (43-85%) compared to field crops, require less water, land and independent of climate, grow on wastewater, can be genetically modified for desirable characters such as amino acid composition and temperature tolerance ².

2. Materials and Materials

The Five cynobacterium strains were isolated and designated as S1, S2, S3, S4 and S5. The reference strain Spirulina was obtained from Oferr Neill Research Centre, Chennai and maintained at Department of Microbiology, HCAS.

The morphology of isolated Spirulina strains were characterized based on their colour of scum, shape, length of filaments, length of spirals, average number of spirals, direction of the helix, distance between the spirals, pitch of spirals, breadth of trichome, presence of gas vacuole, pH and temperature tolerance. The isolated strains were compared with the reference strain and identified as Spirulina platensis. Morphological characters, were observed under low and high power objectives of the compound microscope and measured by micrometry method.

The Spirulina sps strains S1, S2, and S3. Were grown in Zarrouk’s medium under laboratory condition at 35°C in the light chamber for 30 days and estimated the growth parameters like optical density at 560nm, cell population, specific growth rate and doubling time at 30th day.

The effect of the different temperatures (30, 35 and 40°C) on the growth of S1, S2, S3, and reference strains of Spirulina was determined separately. The Zarrouk’s medium was prepared in 1000 ml quantities in a 2 L Erlenmeyer conical flask. Then, sterilized at 15 lbs pressure (1210C) for 20 minutes. The flask were then cooled to room temperature and 50 ml (0.25 mg wet weight) of the 30 days old pure standard inoculum of Spirulina was inoculated separately and incubated for 30 days in BOD incubator at various temperatures viz., 30, 35 and 40°C and periodically replenished with the growth medium to prevent drying up of the cultures. After 30 days of incubation the biomass (dry weight).

The effect of different pH (8.5, 9.0 and 9.5) on growth of S1, S2, S3, and reference strains of Spirulina was determined separately.The Zarrouk’s medium was prepared in 1000 ml quantities in a 2 L Erlenmeyer conical flask and pH of the broth was adjusted with 0.1N NaOH or 0.1N HCl to obtain the different level of pH viz., 8.5, 9.0,and 9.5. Then sterilized at 15 lbs pressure (121 C) for 20 minutes. The flasks were then cooled to room temperature and 50 ml (0.25 mg wet weight) of the 30 days old pure standard inoculum of Spirulina was inoculated separately and incubated for 30 days in light chamber. After 30 days of incubation the biomass (dry weight).

The effect of different levels of sodium chloride (0.05M, 0.1M, and 0.2M) on growth of S1, S2, S3, and reference strains of Spirulina were determined separately. The Zarrouk’s medium was prepared in 1000 ml quantities with different levels of NaCl (0.05M, 0.1M, and 0.2M) in a 2 L Erlenmeyer conical flask. Then, sterilized at 15 lbs pressure (1210C) for 20 minutes. The flasks were then cooled to room temperature and 50 ml (0.25 mg wet weight) of the 30 days old pure standard inoculum of Spirulina were inoculated separately and incubated for 30 days. After 30 days of incubation the biomass (dry weight).

3. Results

The micro algal genera were identified based on their morphological characters like such as colour of scum, shape, filamentous, type of floating and presence of vacuoles under the low and high power of light microscope and pH tolerance of the algae and the locations were represented in Table 1.

The results of morphological characterization of Spirulina sps are presented in Table 2.

The effect of temperature on growth of three Spirulina strains and reference strain was studied and results are recorded in Table 3.

The effect of pH on growth of three Spirulina strains and reference strain was studied and results are recorded in Table 4.

The effect of salinity (NaCl) on growth of three Spirulina strains and reference strain was studied and results are presented in Table 5.

The highest Spirulina biomass obtained at 35°C (1.875 gL-1) and the culture medium presented higher concentrations of phenolic compounds. ⁵ studied the effect of temperature on growth rate, biomass composition and pigment production of Spirulina platensis. Growth kinetics of cultures showed a wide range of temperature tolerance from 20°C to 40°C. Maximum growth rate, cell production with maximum accumulation of chlorophyll and phycobilliproteins were found at temperature 35°C. Similarly, in the present investigation revealed that, all the isolated Spirulina strains recorded the highest rate of growth at 35°C. The highest biomass (0.308 mg ml-1), were recorded in Spirulina-S1 at 35ºC followed by other strains.

The present investigation, the growth of Spirulina strain was studied at different pH levels viz., 8.5, 9.0 and 9.5. All the three Spirulina strains showed the higher rate of growth at pH 9.5 followed by 9.0 and 8.5. The highest biomass (0.312 mg ml-1), were recorded in Spirulina-S1 at pH 9.5. These results are agreement with who found that, the optimum pH for maximum growth and biomass S. maxima was at pH 9.0 to 9.5 ranges.

The present study revealed that, the growth of all the three Spirulina strains showed the higher growth at 0.2 M NaCl followed by 0.05, 0.1 and 0.2M NaCl. The highest biomass (0.312 mg ml-1), were recorded in Spirulina-S1 in saline (NaCl) concentration at 0.2M. These results are agreement with, who have reported that, the optimum micro algal growth was obtained with salinity of 13gL-1 (0.22M).

4. Summary & Conclusion

The effects of temperature, pH, light intensity and salinity on growth of Spirulina strains (S1, S2, and S3) and reference strain (CAS10) were determined in Zarrouk’s medium. The optimum temperature for the growth of all Spirulina strains was found to be 35°C followed by 40°C and 30°C. The highest biomass (0.308 mg ml-1) were recorded in Spirulina-S1 strain at 35°C followed by other strains in 30 days. The effect of pH on the growth of Spirulina strains was studied at various pH levels (8.5, 9.0 and 9.5. The growth of Spirulina strains was the best at pH 9.5. The highest biomass (0.312 mg ml-1) were recorded in Spirulina-S1 strain at pH 9.5 followed by other strains in 30 days. The effect of salinity on the growth of isolated Spirulina strains was studied at 0.05 0.1 and 0.2, M NaCl concentrations. The optimum salinity for the growth of isolated Spirulina strains was found to be 0.2M NaCl concentration and the highest biomass (0.312 mg ml-1), protein (0.190 mg ml-1) and chlorophyll (35.21 µg ml-1) were recorded in Spirulina -S1 followed by strains in 30 days.

The study proved that the Spirulina -S1isolated from marine water showed high bio mass in optimal temperature of 35°C, 9.5 has optimal p^H and 0.2M NaCl concentration as optimal salinity for the mass cultivation of Spirulina in multi stress conditiom.

References