LAUSR

Abstract Sago mill effluent (SME) contains high levels of organic material that can be reused as feedstock for a nutrient source in polymeric bioflocculant fermentation. In this study, SME was reused for bio-based polymeric flocculant or bioflocculant production and was optimised using central composite design (CCD) to obtain a high yield of bioflocculants, chemical oxygen demand (COD) removal, and enhanced flocculating activity. The operational conditions involved in the optimisation were temperature (30–40°C), fermentation time (24–72 h), incubator speed (100–200 rpm), and fermentation medium (sterile and non-sterile SME). Based on the analysis, the optimal conditions for bioflocculant production were a temperature of 30°C, fermentation time of 32 h, incubator speed of 100 rpm, and cultivation in non-sterile SME medium, with bioflocculant yield of 201 mg/L, 65.5% COD removal, and 88.4% flocculating activity. X-ray diffraction analysis showed that the bioflocculants contained C, O, Ca, Mn, Si, P, S, Ca, and Mn. Zeta potential analysis indicated that the bioflocculants had a negative charge, while analyses via liquid chromatography-mass spectrometry (LC-MS) revealed that the bioflocculants consisted of glucose, xylose, and rhamnose. Therefore, reusing SME at optimum operational conditions to produce a new product and minimise waste discharge to the environment could support and move towards the circular economy concept.