Optimization of the growth condition of S. platensis
The optimization of appropriate media for optimum cultivation of
S. platensis was very important. Four different types of media
viz. Zarrouk’s modified medium, Zarrouk’s medium, BG-11 and F-2 medium were to initiate culture of Spirulina (Fig 1). The maximum growth of culture was observed in Zarrouk’s modified medium with 0.641 gm/ml, followed by 0.610 gm/ml on Zarrouk’s medium as compared other medium (Table 1). Zarrouk’s medium is also reported as appropriate medium for S
. platensis growth by
Devanathan and Ramanathan, 2013. In 2016, Rajasekaran
et al. used modified Zarrouk’s medium in which they added potassium nitrate (KNO
3) despite of sodium nitrate (NaNO
3) and they suggested that SP-6 and CCMB strains of
S. platensis could be used for higher growth with Zarrouk’s modified medium as compared with Zarrouk’s medium. Michael
et al.,
(2019) used cost-effective culture medium (LCMA) that exhibited
Spirulina growth in large scale with maximum 0.75 gm/100 ml of dry weight, 0.99% chlorophyll level and maxim um absorbance (2.06 at day 15) than the Zarrouk’s medium.
Fanka et al., 2022 also evaluate the biomass production and biomolecule concentrations of
Spirulina species in Zarrouk’s medium, BG-11 and modified Zarrouk’s medium, which has reduced nitrogen (40%), carbon (83%), magnesium (63%) and phosphorus (94%). In their study Zarrouk’s modified medium gave maximum growth of
Spirulina species (0.19 gm/l/d) as well as 21.6% carbohydrates which is 160% higher as compared to Zarrouk’s medium. In the present study also, a modified Zarrouk’s medium showed higher biomass production of
Spirulina platensisin comparison to other medium.
Cell counting
The maximum number of cells of
S. platensis was observed from Zarrouk’s modified medium
i.e. 4,00,000 average no. of cell/ml, followed by Zarrouk’s medium with 2,00,000 average no. of cell/ml as shown in Table 2. The cell count 98000 average number of cells per ml was recognized from BG-11 Spirulina culture. The least average number of cells in one ml of
Spirulina culture
i.e. 92000 was found from F-2 medium. The results indicated that the Zarrouk’s modified medium was the optimum medium for significant growth of
S. platensis. The similar results were obtained from
Rajasekaran et al., (2016) in which Spirulina gave optimum growth in Zarrouk’s modified medium.
Abd El-Monem et al., (2021) reported Zarrouk’s medium as the most prominent medium for better cultivation of
S. platensis. On the other hand,
Joshi et al., (2018) revealed that BG-11 medium is more effective to cultivate specific growth of Spirulina in comparison to Walne and CHU medium.
Analysis of pigment proteins
Phycocyanin
Among the phycobiliproteins, phycocyanin plays a vital role in numerous fields with highest economic value. Hence
S. platensis attains more attention for large scale biomass production with simple procedures (
Chofamba, 2021). Fig 2 showed the calculated data of the phycocyanin contents in the different medium of the
Spirulina platensis. As compared to other
Spirulina culture medium, the maximum phycocyanin level (0.19 mg/ml) was observed in Zarrouk’s modified media of
S. platensis. Thereafter 0.12 mg/ml and 0.1 mg/ml phycocyanin content was observed in Zarrouk’s medium and BG-11 media, respectively. The lowest concentration (0.08 mg/ml) of phycocyanin was observed with F-2 media of
Spirulina.
Ali et al., (2014) reported high phycocyanin content (0.15 mg/ml) in ethyl acetate extract of
S. platensis cultivated in Zarrouk’s medium. UV spectrometer and Liquid chromatography–diode-array detection (LC-DAD) method were used by
Park et al., 2018 to identify phycocyanin concentration from seven different
Spirulina products with freeze-dried
S. platensis trichomes cultures in which maximum phycocyanin level (251.2 mg/gm) was detected with
S. platensis trichomes and 94.9-153.3 mg/gm average range in spirulina products. A study conducted by
Chofamba, 2021 revealed that lowest illumination is appropriate to maximum PC level from
S. platensis cultured on modified Zarrouk’s medium.
Total carotenoids
Carotenoids is a significant natural pigment among the other pigments which is present in algae (
Borowizka, 1988), few fauna and all vascular flora (
Zeb and Mehmood, 2004). Carotenoids have yellow–orange–red color that is dissolved with hydrophobic solvents. It has vital applications in various fields such as food and cosmetics industry and therapeutic purposes especially for anti-oxidant properties that are responsible to increase large scale production of carotenoids (
Borowizka, 1988). As similar to phycocyanin results in this research, maximum total carotenoid content was also observed with Zarrouk’s modified media, followed by Zarrouk’s medium containing
S. platensis culture in comparison to other media. The total carotenoid content of
S. platensis was 5.99 µg/ml with Zarrouk’s modified media, 5.51 µg/ml with Zarrouk’s medium, 4.48 µg/ml with BG-11, while F-2 medium contains minimum amount of carotenoid (3.08 µg/ml) as shown in Fig 3.
Devanathan and Ramanathan, (2013) reported the highest carotenoid results.