Comparative analysis of novel MBN medium for Chlorella vulgaris cultivation: Growth dynamics and fatty acid profiles

Abstract

Microalgae cultivation underpins various commercial applications, yet studies exploring media composition that provides a balanced growth and lipid composition scarcely appear in the literature. This study evaluated a novel low-cost medium (MBN, molasses, baker’s yeast and NPK fertilizer) at three strengths against standard algal medium (Chu-10, BG-11 and additive-free water) for the cultivation of Chlorella vulgaris. The algal culture in 1 L cylinders was tracked for cell density, for over eight weeks. The composition of lipids and relevant molecules in the algal biomass was also monitored by GC-MS. The highest algal dry weight (697.8 mg) and productivity (155% L-1 day-1) were obtained in MBN2 (0.2x strength). This medium sustained proliferation to 1.18 x 106 cells mL-1 by week 6 and maintained the highest density (1.105 x 106 cells mL-1). In contrast, MBN3 (0.3x) showed early expansion of algal cell density that remained stagnant. Final chlorophyll content reached to 27.87 mg mL-1 in MBN2 and 28.54 mg mL-1 in BG-11 with area under-curve ranking favoring MBN2. The analysis of lipids showed that in additive-free water, C. vulgaris produced a simplified lipid profile (dominated by C14:0) indicated about stressed growth. While MBN3 promoted a diversified lipid profile (20 different compounds) and induced unsaturated fatty acids yielding a balanced SFA:UFA ratio (0.7:1). The compound C18:1 was only produced in Chu-10 medium. MBN formulations triggered the highest fatty acid methyl esters and long-chain alcohols indicating alternate carbon sinks. PCA analysis clustered Chu-10, BG-11 and MBN1owing to limited metabolic divergence. MBN2 appeared as a better medium for biomass and for biofuel while MBN3 can be used as a supplement to provide polyunsaturated fatty acids.