Optimisation of phycocyanin production from microalga Arthrospira (Spirulina) maxima

Phycocyanin is one of the valuable pigments produced by Arthrospira spp. that possess nutritional and colouring properties. It has been widely used in food, nutraceutical and biotechnology applications. Presently, Arthrospira platensis is very much established for producing phycocyanin commercially. Given how abundant and widely understood it is, this leaves room for less utilised yet promising strains like Arthrospira maxima to be studied for pigment production. The study aims to optimise the phycocyanin production from the Arthrospira maxima strain by first considering which of these media components are vital factors toward phycocyanin secretion by the microalgal cells, i.e., sodium nitrate, sodium bicarbonate, dipotassium phosphate and sodium chloride and precursor. Upon identifying the most significant factors, their composition in the production medium would be manipulated using response surface methodology (RSM). Subsequently, the environmental effect of cultivating A. maxima inside the column photobioreactor was investigated. The preliminary result indicates that the Nallayam Research Centre Media (NRCM) was the best option, as it has produced slightly higher phycocyanin production (163.12 mg/L) and dry cell weight (1.25 g/L) than the Zarrouk Media (ZM) and Central Food Technological Research Institute Media (CFTRIM). The preliminary screening using the Plackett-Burman design showed two macronutrients and a precursor significantly affecting the target response (ρ>0.05): sodium nitrate, dipotassium phosphate and glutamic acid. The three factors were further refined using the Box-Behnken design (BBD). BBD's highest phycocyanin concentration was 224.86 mg/L, achieved at a recipe comprising of 0.0125 M sodium nitrate, 0.375 mM dipotassium phosphate and 0.625 mM L-glutamic acid. This resulted in a 37.85% improvement over the unoptimised NRC medium. BBD's validating recipe comprising 0.0125 M sodium nitrate, 0.375 mM dipotassium phosphate and 0.625 mM L-glutamic acid produces 235.98 mg/L of phycocyanin. It has a 44.67% improvement in term phycocyanin concentration compared with an unoptimised NRC medium. In the column photobioreactor setup, an aeration rate of 0.5 L/min yielded the highest phycocyanin concentration (560.30 mg/L) and biomass (4.4 g/L), surpassing rates of 0.25 L/min, 0.75 L/min, and 1.0 L/min, all maintained under a consistent light intensity of 40.5 ± 4.73 μmol/m2/s. This configuration resulted in a 137.44% increase in phycocyanin concentration and a remarkable 214.29% increase in biomass compared to the validation model. Alternatively, with aeration remained fixed at 0.5 L/min, the same reference light intensity of 40.5 ± 4.73 μmol/m2/s still registered the highest phycocyanin concentration (560.30 mg/L). In contrast, a higher light intensity of 101.25 ± 6.75 μmol/m2/s was eventually optimal to produce the highest A. maxima biomass density (6.2 g/L). In conclusion, optimizing the composition of medium could enhance phycocyanin production by Arthrospira maxima, and culturing Arthrospira maxima in a bubble column photobioreactor with optimal light intensity and aeration may increase phycocyanin concentration.

Text 124987 fulltext.pdf Download (1MB) Official URL or Download Paper: https://ethesis.upm.edu.my/id/eprint/18791

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