LAUSR

Purpose The aim of this study was to optimize the enzymatic hydrolysis of palm oil mill effluent (POME) to release fermentable sugar as a platform convertible to value-added product i.e. bioflocculant. Methods A Plackett–Burman design followed by a central composite design of response surface methodology was applied to optimize the enzymatic hydrolysis of POME to release fermentable sugars. Subsequently the enzymatic hydrolysate of POME was used to produce bioflocculant (BM-8) using POME-isolated Bacillus marisflavi NA8. The produced BM-8 was then characterized and its potential in microalgae harvesting was explored. Results Pure substrate (100%, v/v) dosed with 1% (v/v) enzyme and agitated at 200 rpm yielded optimum fermentable sugar from POME hydrolysate. Subsequently, the medium produced 9.72 g/L of BM-8 during 24 h of cultivation. The BM-8, which composed primarily of polysaccharide (74%) and protein (25%) with 1% nucleic acid was found to be thermally stable and able to withstand a wide pH range, with its optimum tolerance at pH 6. Additionally, the BM-8 was found efficient (90% biomass recovery in 30 min) for precipitation of Chlorella vulgaris , thus suggesting its great potential as a flocculating agent. Conclusion The study demonstrated that POME hydrolysate may be used as a cheap and renewable substrate for BM-8 production. In addition, BM-8’s flocculating capability showed it potential to substitute hazardous chemical flocculants. Graphical Abstract