Characterization and flocculation properties of a carbohydrate bioflocculant from a newly isolated Bacillus velezensis 40B.

In this study, a bioflocculant with a high flocculation activity (>98%) produced by strain 40B, which was isolated from a brackish water was investigated. By 16S rDNA sequence analysis, strain 40B was identified as Bacillus velezensis. Chemical analysis of the bioflocculant 40B indicated that it contained 2% protein and 98% carbohydrates. FTIR analysis showed the presence of carboxyl, hydroxyl and amino groups, which were preferred for the flocculation process. The optimal concentration for the flocculation activity was 3.5 mg l-1. This polysaccharide could also flocculate kaolin suspension over a wide range of pH (1–10) and temperature (5–85 °C) in the presence of CaCl2. The stability of the bioflocculant 40B under various conditions suggests its possible use in the industries and environmental applications. However, no previous report exists on the isolation and characterization of a bioflocculant from the Bacillus velezensis.

Identification of bacterial strains from tannery effluent and reduction of hexavalent chromium.

Four chromium-resistant bacteria were isolated from tannery effluent collected from Burgelarab, Alexandria, Egypt. These isolates displayed different degrees of chromate reduction under aerobic conditions. Based on 16S rDNA gene sequence analysis, two of them (S3 and S4) were identified as Acinetobacter, and Pseudomonas, respectively. The minimum inhibitory concentration for Acinetobacter sp. strain S3 was 160 mg l-1, while it was 200 mg l-1 for Pseudomonas sp. strain S4. However, strain S4 was able to reduce a wide range of Cr (VI) concentrations from 20 to 200 mg l-1; while, it was reducing 64.4% of Cr (VI) at 160 mg l-1 within 72 hr. Immobilization experiments demonstrated that strain S4 in calcium alginate gel matrix was more effective than the using of free cells in chromium reduction.