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.

Microorganisms have a high potential as biofuel sources. Co-culture of microalgae and yeasts can result in high lipid production as a modification treatment. The goal of this study was to see how the co-culture of the Glagah consortium (diversity of associated microalgae and bacteria from Glagah Lagoon, Yogyakarta) and Lipomyces starkeyi affected the production of biomass, lipids, proteins, and carbohydrates. The culture was performed under airtight conditions on a shaker at 127 rpm, with a light intensity of 27.75 mol/m2/s and a temperature of 30°C. The culture was subjected to a dark: light (6:18) treatment. Biomass was measured by dry weight, lipids by the Bligh and Dyer method, proteins by the Bradford method and carbohydrates by the phenol-sulfuric acid method. On day 3, L. starkey culture produced the most biomass, yielding 2.21 g/L with a productivity of 0.49 g/L/day. On day 4, the highest lipids produced from co-culture treatment yielded 1.03 g/g with a productivity of 0.21 g/L/day. The highest protein yield was obtained from L. starkeyi culture treatment on day 4, yielding 0.60 g/g with a productivity of 0.12 g/L/day. On day 6, co-culture produced the total carbohydrates, yielding 4.78 g/g with a productivity of 0.68 g/L/day. The co-culture treatment produced the highest lipids and carbohydrates production (1.03 g/g and 4.78 g/g) and productivity (0.21 g/L/day and 0.68 g/L/day), while L. starkeyi culture produced the highest total biomass and protein production (2.21 g/L and 0.6 g/g)  and productivity (0.49 g\L\day and 0.12 g/L/day). In microalgae culture, CO2 generally given directly through the aeration process. In this study, the source of CO2 was yeast, whereas yeast also obtained O2 from microalgae in the consortium for their metabolic process. This mutualism symbiosis will help in providing benefits in reducing the costs for the cultivation process, especially in optimizing the production of biomass an lipids.