Biosorption of Cadmium by Non-Toxic Extracellular Polymeric Substances (EPS) Synthesized by Bacteria from Marine Intertidal Biofilms

Abstract

Cadmium is a major heavy metal found in polluted aquatic environments, mainly derived from industrial production processes. We evaluated the biosorption of solubilized Cd2+ using the extracellular polymeric substances (EPS) produced by Bacillus sp. MC3B-22 and Microbacterium sp. MC3B-10 (Microbactan); these bacteria were originally isolated from intertidal biofilms off the coast of Campeche, Mexico. EPS were incubated with different concentrations of cadmium in ultrapure water. Residual Cd2+ concentrations were determined by Inductive Coupled Plasma-Optic Emission Spectrometry and the maximum sorption capacity (Qmax) was calculated according to the Langmuir model. EPS were characterized by X-ray photoelectron spectroscopy (XPS) before and after sorption. The Qmax of Cd2+ was 97 mg g−1 for Microbactan and 141 mg g−1 for MC3B-22 EPS, these adsorption levels being significantly higher than previously reported for other microbial EPS. In addition, XPS analysis revealed changes in structure of EPS after biosorption and showed that amino functional groups contributed to the binding of Cd2+, unlike other studies that show the carbohydrate fraction is responsible for this activity. This work expands the current view of bacterial species capable of synthesizing EPS with biosorbent potential for cadmium and provides evidence that different chemical moieties, other than carbohydrates, participate in this process.

Inorganic Phosphate Solubilization by a Novel Isolated Bacterial Strain Enterobacter sp. ITCB-09 and Its Application Potential as Biofertilizer

“…This study shows that Enterobacter sp. ITCB-09 produces a biopolymer of glycoprotein nature, which suggests functional groups that may have calcium chelating activity [36,49]. Recently, Costa et al [13] suggested the ecological role of bacterial EPS in the aggregation of soil particles, highlighting that EPS are directly involved in the formation of organo-mineral associations in the soil, affecting the composition of immobile and mobile organic matter, as well as the reactivity of minerals.…”

“…Hexuronic acids were also present. These compounds may interact with insoluble inorganic phosphate and convert it to a soluble form, via their ionizable functional groups such as carboxyl, carbonyl, or amino [49]. Most of the plants, including the control, germinated between 10 and 15 days ( Table 5).…”

Heavy metal induced stress on wheat: phytotoxicity and microbiological management

“…271 Due to these properties, the EPS released by many aerobic soil bacteria have been reported to participate in metal removal from polluted environment. 245 As an example, 272 explained the Aer binding, the EPS of Azotobacter creates a microenvironment in the soil, which is composed of metal ions essentially required for regulating the soil ecology. It thereby promotes the normal growth and development of plants.…”

Treatment of Solid Waste Containing Metals by Biological Methods

“…MC3B-10 and Bacillus sp., respectively, the maximum sorption capacity of Cd 2+ was 97 mg/g for Microbactan and 141 mg/g for B. firmus EPS, both at pH 7 and 28°C. In addition, microbactan and B. firmus exopolymeric substances (EPSs) were nontoxic to Artemia salina nauplii, which is an aquatic model organism widely used in aquaculture activities [59].…”