Optimisation of Bioflocculation Using Anabaena sp. and Navicula sp. for Harvesting of Glagah Microalgae Consortium

Abstract

One of the problems in microalgae is harvesting. Currently, many chemical methods are used that impact the environment. Not all of them can be used as a filter, so bioflocculation is used because there is no need to change the medium. This method is an environmentally friendly and efficient alternative to chemical flocculants that usually cause contamination of biomass and health. Previous studies have shown that different ratios of auto-flocculated microalgae in cocultures affect the flocculation rate. This research was carried out by the Glagah Consortium bioflocculation using Anabaena sp. and Navicula sp., which had never been done before. The study aims to study the effect of the mixing ratio on the flocculation rate, carbohydrates, and lipid content of the Glagah Consortium. The consortium uses Anabaena sp. and Navicula sp. as bioflocculants. Glagah and Anabaena sp. consortium was cultured in Bold Basal Medium, while Navicula sp. was cultured in F/2 medium. Cell density was measured every 24 hr for 8 days with a hemocytometer. The cultures were harvested in the stationary phase, then mixed between non-flocculated microalgae (Glagah Consortium) and flocculated microalgae (Anabaena sp., Navicula sp.) in a ratio of 1:1, 1:0.5, and 1:0.25 for 24 hr. Bioflocculation was measured by spectrophotometer at 750 nm 0 and 24 hr after mixing. Carbohydrate levels were measured using the phenol sulfuric acid method, while lipid measurements were performed using the Bligh and Dyer method. The addition of Anabaena sp. and Navicula sp. as bioflocculant in Glagah Consortium culture results in an increase in flocculation rate with an effective ratio of 1:0.25 for Anabaena sp. (81%) and 1:1 for Navicula sp. (95%). Mixing of Anabaena sp. and Glagah Consortium results in carbon source competition, reducing carbohydrate content at higher mixing ratios (0.172, 0.364, and 0.500 mg/ml on 1, 1:0.5, and 1:0.25) while increasing lipid content as a result of lipid production in stationary phase (highest on ratio 1:1 = 0.011 mg/ml). Navicula sp. and Glagah Consortium mixture caused no significant changes to carbohydrate content but showed an increased amount of lipid at all ratios as a result of osmotic stress on Glagah Consortium from saline F/2 medium (highest on ratio 1:1 = 0.162 mg/ml).