Cold-Shock Stress Induces Formation of a Biopolymer Flocculant by Bacillus alvei NRC-14 under Static Incubation Conditions

Bacillus alvei NRC-14, a soil bacterial isolate, was found to exhibit multiple-adaptive response when exposed to abiotic stress factors. In the present study, chemical and flocculation properties of a viscous biopolymer flocculant produced by the strain under cold-shock stress are investigated. Addition of sucrose or starch at a 1% concentration increased the growth and viscosity. The biopolymer flocculant is a polysaccharide as indicated by the sugars content. Maximum values of viscosity and flocculating activity were obtained at a pH range from 5-9. Acidic or alkaline pH values reduced both of the viscosity and flocculating activity. IR-spectra revealed various active and functional groups such as carboxyl, hydroxyl, methoxyl, and urinate by which strong and large flocs are formed. The biopolymer flocculant showed thermal stability and good flocculating properties.