The Effect of Tofu Wastewater and pH on the Growth Kinetics and Biomass Composition of Euglena sp.

Media and pH are two crucial factors in microalgal cultivation. Industrial wastewater such as tofu wastewater can be utilized as alternative media for growing microalgae like Euglena sp. to produce biomass as feedstock in biorefinery activities. Here, we evaluated combinations of tofu wastewater (L) consisting of 0% (L₁), 75% (L₂), and 100% (L₃) with pH (P) levels consisting of 5.0 (P₁), 5.5 (P₂), 6.0 (P₃), 6.5 (P₄), and 7.0 (P₅). The analyses were carried out on the growth kinetics, biomass, primary metabolite compounds, and pigments of Euglena sp. Based on the study, the combinations with the highest cell density, biomass, maximum carbohydrate content, maximum lipid content, and protein content were L₂P₂ (23.13x10⁵ cells/ml), L₂P₁ (4.53±0.17 mg/ml), L₁P₅ (0.93±0.02 mg/ml), L₂P₁ (1.27±0.11 mg/ml), and L₃P₄ (256±26.86 ppm), respectively. Moreover, the combinations with the highest chlorophyll-a, chlorophyll-b, and carotenoid were L₂P₄ (33.53±0.13 mg/l), L₂P₂ (17.73±0.50 mg/l), and L₂P₂ (11.65±0.00 mg/l), respectively. The addition of tofu wastewater combined with specific pH level enhanced the growth and biomass composition of Euglena sp. (P<0.05), with the exception of carbohydrate content. Additionally, each biochemical component of Euglena sp. had a different optimum combination of tofu wastewater and pH level. However, this wastewater can potentially be used as an alternative medium for cultivating this microalga in order to cut the production costs of biorefinery activity.