A novel bioflocculant produced by Enterobacter aerogenes and its use in defecating the trona suspension

Abstract

In this paper, a bioflocculant-producing bacterium, named W-23, was isolated from soil and identified as Enterobacter aerogenes. The bioflocculant (named WF-1) produced by W-23 was an acidic polysaccharide composed mainly of uronic acid (13.2%), pyruvic acid (7.4%) and acetic acid (1.6%). The three components sugars of WF-1 were glucose, fructose and manose, and the molar ratio was 10.3:5.4:1 for glucose:fructose:manose. The influence of factors like temperature, bioflocculant dosage and concentration of positive ions on the flocculation were studied. The optimal conditions were as follows: temperature 45 °C, WF-1 90 mg/L and Zn²⁺ 0.03 mol/L. As a result, the sedimentation rate was 2.96 × 10⁻⁴ m/s, and the OD of supernatant reached 0.05. The efficiency of the bioflocculant was better than that of conventional chemically synthesized flocculants, such as anionic polyacrylamide or non-ionic polyacrylamide.

Introduction

Trona is an important mineral for producing some chemical compound, such as sodium carbonate, sodium bicarbonate, sodium hydroxide and Glauber's salt. Trona often consists in trona ore or trona lake. The soluble salts Na₂CO₃, NaHCO₃, Na₂SO₄ and NaCl, and insoluble matter CaCO₃, clay, sludge, quartz and calcite are the main component parts of trona. In order to separate trona from clay or sludge during industrial production, the chemically synthesized flocculants, such as polyacrylamides, were commonly used because of their effectiveness and low cost. However, it is evident that the acrylamide monomer is a strong carcinogen and neurotoxic to humans [1]. Because of these concerns, the uses of the chemically synthesized flocculants are limited.

Bioflocculants (microbial flocculants), which are produced by microorganisms during their growth, have received considerable scientific and biotechnological attention in recent years because of their biodegradability, harmlessness and lack of secondary pollution of their degradative intermediates [2], [3]. It was described that some types of bioflocculants had efficient flocculating activities [2]. In particular, some bioflocculants are applied in the treatment of wastewater with nearly neutral pH [4], [5], [6]. While there were few reports about the defecation of strong alkaline trona suspension by bioflocculants.

In this study, screening and isolation of a new flocculant-producing strain were described. Investigations of the bioflocculant that it produced (WF-1) and its application in treatment of the trona suspension were reported.