Bacillus mojavensis strain 32A, a bioflocculant-producing bacterium isolated from an Egyptian salt production pond

► About 16 bacterial isolates were screened for their ability to produce bioflocculants. ► The most efficient one was identified as Bacillus mojavensis strain 32A was able to produce 5.2g/L of purified bioflocculant. ► Characterization of biopolymer revealed that it is a heteropolysaccharide. ► The flocculation and sedimentation efficiency of the purified polymer was examined. Bacillus mojavensis strain 32A that exhibited 96.11% flocculation efficiency for clay suspensions was selected from other 15 comparative strains. Under growth condition, strain 32A was able to produce 5.2g/L of purified biopolymer. Its constituent was mainly polysaccharide and protein with proportional of 98.4–1.6% respectively. FTIR spectrum was confirming its chemical analysis. This biopolymer attain very fast sedimentation rate. The cost-effective biopolymer and CaCl2 dosages were 3mg/L and 5ml/L respectively that posed 89.7% flocculation efficiency. These dosages were suitable only for clay concentrations ⩽5g/L. The maximum flocculation efficiency of the biopolymer recorded at pH 1.0 of clay suspension. The too high (>75°C) or too low (