Date of Award

3-2-2026

Thesis Type

PhD

Document Type

Thesis

Divisions

Faculty of Engineering

Department

Department of Chemical Engineering

Institution

Universiti Malaya

Abstract

Arthrospira platensis (Spirulina) is a filamentous cyanobacterium valued for its nutritional profile, particularly the pigment–protein phycocyanin, with potent antioxidant and anti-inflammatory properties. Despite its industrial significance, large-scale commercialization remains constrained by high cultivation costs and inefficient extraction methods. This study investigated the use of food-based industrial wastewater as an alternative nutrient medium for Spirulina cultivation, aiming to reduce production costs, enhance phycocyanin yield, and support sustainable wastewater remediation. Three types of food-based wastewater with different nutrient composition (WW1, WW2, WW3) was diluted with Kosaric medium (1:1) and used for Spirulina cultivation. The highest biomass concentration was achieved in WW2 (1.93 g L⁻¹), followed by WW1 (1.88 g L⁻¹), the control (1.87 g L⁻¹), and WW3 (1.78 g L⁻¹). Significant nutrient removal was observed during cultivation, with WW2 reducing ammoniacal nitrogen, nitrate, nitrite, and total phosphorus by 63.2%, 62.0%, 87.6%, and 93.4%, respectively, confirming the dual benefit of biomass production and wastewater bioremediation. Besides, techno-economic analysis revealed that WW2 achieved the lowest cultivation cost of USD 430.05 per kg of biomass, representing a 51.6% reduction compared to the control (USD 887.70). Optimization using Kosaric medium established pH 9.8 and an 18-hour photoperiod as ideal conditions for maximizing phycocyanin yield. With these parameters fixed, subsequent optimization in wastewater identified wastewater concentration as the most influential factor, followed by inoculum ratio and light intensity. Maximum phycocyanin yields were 0.472 mg mL⁻¹ in WW2, 0.284 mg mL⁻¹ in WW1, and 0.175 mg mL⁻¹ in WW3, with all models showing strong statistical significance (R² > 0.86). Characterization analysis such as Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FESEM) confirmed no significant differences in composition or structure between wastewater-grown and control-grown Spirulina. Meanwhile, phycocyanin from wastewater-grown Spirulina exhibited comparable properties to the control with toxicity assays indicated no cytotoxic effects, while antioxidant and anti-inflammatory activities demonstrated strong bioactivity properties. On the other hand, extraction performance was compared among three non-conventional methods. Ultrasound-assisted extraction (UAE) yielded 202.76 mg g⁻¹ phycocyanin with a purity ratio of 2.05, while pulsed-electric field (PEF) achieved the highest yield of 156.61 mg g⁻¹ with a purity ratio of 3.69. High-voltage electric discharge (HVED) outperformed both, delivering 221 mg g⁻¹ yield with a purity ratio of 6.3 in just one minute at a 0.1% biomass-to-solvent ratio. Energy analysis confirmed HVED and PEF are more efficient than UAE. At a 0.10% solvent ratio, UAE energy demand rose from 8.65×10⁻⁴ kWh (1 min) to 6.07×10⁻³ kWh (7 min), whereas PEF and HVED increased from 6.17×10⁻⁴ to only 4.26×10⁻³ kWh, approximately 30% lower than UAE. These results demonstrate HVED is effective in achieving both high yield and purity with reduced energy and time requirements. Overall, food-based industrial wastewater represents a sustainable and cost-effective medium for Spirulina cultivation, enabling simultaneous nutrient remediation and biomass production. By combining optimized cultivation with HVED-based extraction, this work establishes a scalable and energy-efficient pathway for high-quality phycocyanin production, advancing Spirulina’s role in sustainable biotechnology and the circular bioeconomy.

Initial

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Additional Information

Thesis (PhD) - Faculty of Engineering, Universiti Malaya, 2026.

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