Production and characterization of biopolymer as bioflocculant from thermotolerant Bacillus subtilis WD161 in palm oil mill effluent Wilaiwan Chaisorn a , Poonsuk Prasertsan a,* , Sompong O-Thong b , Pawadee Methacanon c a Department of Industrial Biotechnology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, 90112, Thailand b Department of Biology, Faculty of Science, Thaksin University, Phatthalung, 93110, Thailand c National Metal and Materials Technology Center (MTEC), Pathumthani, 12120, Thailand article info Article history: Received 24 March 2016 Received in revised form 4 June 2016 Accepted 4 June 2016 Available online xxx Keywords: Bacillus subtilis Biopolymer Characterization Palm oil mill effluent Bioflocculant abstract Five bacterial strains were screened for polymer production in five synthetic media (GP, PS, GL, PL and PR). The highest polymer yield was obtained from Bacillus subtilis WD161 in PR medium (8.89 g/L). Cultivation at 30, 45 and 60  C indicated that they were thermotolerant with the maximum biopolymer yield at 45  C. Using palm oil mill effluent (POME) as me- dium, the nitrogen had to be supplemented to 1.28 g/L (equal to that in PR medium) with the initial pH adjusted to 7.0 and cultivation at 30  C. Characterization based on its composition and functional groups revealed that the biopolymer WD161 was glycoprotein with the molecular weight of 1.54  10 6 Da. FT-IR analysis revealed the presence of amine (NH 2 ), hydroxyl, carboxyl and carbonyl groups. It was also a bioflocculant and its floccu- lating activity to precipitate the suspended solid in POME increased by 35% under the optimum condition. © 2016 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. Introduction Biopolymers have received an increased interest due to more environmentally awareness of consumers, the limitation of crude oil and global warming problem. Biopolymers should be produced from renewable sources and biodegradable so that they would have a less negative effect on our environment compared to petroleum based materials [1]. Production of biopolymer from microorganism is influenced by many fac- tors such as temperature, pH, carbon and nitrogen sources, ion source, aeration rate and carbon to nitrogen ratio [2]. Many bacteria produce a wide range of extracellular polymeric substances composed of polysaccharides, proteins, lipids and other biological macromolecules, that could be adhesion to surfaces, aggregation in suspended cultures or biofilms, and bioflocculant, etc. [3]. There are various types of bioflocculant such as glycoprotein polymer from Bacillus subtilis DYU1 giv- ing the highest flocculating activity of 97% in kaolin suspen- sion [4], protein polymer from Rhodococcus erythropolis S-1 [5] and Nocardia amarae YK1 [6]. Bacillus mucilaginosus MBFA9 produced glycoprotein polymer and used as bioflocculant for treatment of wastewater from starch industry to remove COD (68.5%) and suspended solid (85.5%) [7]. Glycoprotein polymer * Corresponding author. Fax: þ66 74 558866. E-mail address: poonsuk918@yahoo.com (P. Prasertsan). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy xxx (2016) 1 e8 http://dx.doi.org/10.1016/j.ijhydene.2016.06.045 0360-3199/© 2016 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. Please cite this article in press as: Chaisorn W, et al., Production and characterization of biopolymer as bioflocculant from thermoto- lerant Bacillus subtilis WD161 in palm oil mill effluent, International Journal of Hydrogen Energy (2016), http://dx.doi.org/10.1016/ j.ijhydene.2016.06.045