The effect of Culture Medium and pH Variation on the growth of two Microalgae Species: Scenedesmus quadricauda and Chlorella vulgaris

This in-depth study is meticulously designed with the main aim of evaluating and elucidating the complex influence that pH level and specific composition of the culture medium exert on the growth dynamics of two microalgal species (Scenedesmus quadricauda and Chlorella vulgaris). To achieve this objective, two distinct series of meticulously structured experiments were carried out: in the initial experimental series, pH was systematically adjusted to a value of 8.5, while in the subsequent experimental series, it was deliberately set at a significantly lower level of 5. Each of these experimental series comprised three unique culture conditions: one using BBM medium, known as Bold's basal medium, another using an equimolar mixture of BBM and F/2, known as Guillard's F/2 medium, and a third consisting solely of F/2 medium. The results of these experiments clearly indicate that microalgal growth is subject to significant variation as a direct function of these specified parameters. In particular, the Scenedesmus quadricauda species reaches its optimum stage of growth and development when grown in BBM medium at a reduced pH of 5, with the highest cell density meticulously observed on the twelfth day of the culture period. Conversely, the microalgal species Chlorella vulgaris exhibits higher growth efficiency when grown in the BBM+F/2 mixture under alkaline conditions at pH 8.5, with its maximum growth performance meticulously recorded on day eleven of the experimental timeline. Furthermore, rigorous statistical analysis using SPSS software in conjunction with Tukey's test confirmed the statistical significance of these observed differences, indicating that the Scenedesmus species adapts better to acidic environmental conditions, while chlorella prefers to thrive in a nutrient-rich alkaline environment. These significant results underline the crucial importance of carefully selecting both the pH level and the nutrient composition of the culture medium in order to optimize the production and cultivation of these specific microalgae species.