# Biosorption of Heavy Metals by the Bacterial Exopolysaccharideaccharide FucoPol
## 1 Introduction  
Heavy metals are elements naturally found throughout the earth's crust. They have a high atomic number and a density at least 5 times higher than water (1 g/cm\({}^{3}\)) [1, 2]. Despite being required for several biological processes (i.e., protein, nucleic acids, carbohydrate and lipid metabolism), they are also essential for our industry and daily life. Heavy metal sources include activities such as burning fossil fuels, mining, smelting and electroplating. They are also present in paints, batteries, metal products (e.g., ammunitions and pipes), cosmetics, electronic equipment, ceramics, fertilizers, pesticides, and wood preservatives [3, 4]. Despite their widely utilization, heavy metals can cause serious toxicity issues in living organisms [3]. These metals are extremely poisonous and can eventually be lethal, since they inhibit essential metabolic pathways, cause oxidative stress and cellular damages, and can promote mutagenesis [2, 4, 5]. Co\({}^{2+}\), for example, has only one biological function as a component of vitamin B\({}_{12}\), nevertheless it can be toxic at high levels. Co\({}^{2+}\) exposure might occur due to inhalation or ingestion of food and drinking water containing Co\({}^{2+}\), and can cause neurological, cardiovascular, and endocrine problems such as cardiomyopathy, vision and hearing impairment, reversible hypothyroidism, and polycythemia [6, 7]. Cu\({}^{2+}\) is a trace nutrientessential for enzymatic activity and redox reactions due to its capacity to cycle between Cu\({}^{2+}\) and Cu\({}^{+}\). However, this transition to the reduced state can generate hydroxyl and superoxide radicals that can damage living cells [2,4]. Cu\({}^{2+}\) exposure occurs by ingestion of water and can cause liver and kidney damage, anemia and irritation of the gastrointestinal track [1]. Although Zn\({}^{2+}\) deficiency causes health problems, Zn\({}^{2+}\) overexposure can cause cholesterol, anemia, nausea, vomiting, abdominal pain and lethurgy [4]. Pb\({}^{2+}\) is considered carcinogenic and highly toxic, it can bind and inactivate enzymes and proteins, substitute essential ions in the cells (Ca\({}^{2+}\), Mg\({}^{2+}\), Fe\({}^{2+}\), and Na\({}^{+}\)), and inhibit Ca\({}^{2+}\) transport. Moreover, Pb\({}^{2+}\) fastens the formation of reactive oxygen species (ROS) that causes oxidative stress and damages in living cells [3,4,8]. Pb\({}^{2+}\) is absorbed and distributed into the human tissues after inhalation of Pb\({}^{2+}\)-contaminated dust or aerosols, and ingestion of contaminated water or food [2,3]. Pb\({}^{2+}\) poisoning severely affects the nervous system, causing edema, encephalopathy, and brain damage [3]. Even low-level Pb\({}^{2+}\) exposure is associated with liver/biliary injuries [9]; decreased kidney function and chronic kidney disease incidence [10]; and cardiovascular problems such as hypertension, electrocardiographic abnormalities, left-ventricular hypertrophy, peripheral arterial disease and cardiovascular disease mortality [11]. According to the US Environmental Protection Agency, the maximum concentration of Cu and Zn in drinking water is 1.3 and 5 mg/L, respectively, a much higher value than of Pb (0.015 mg/L), due to their lower toxicity to humans. However, Cu\({}^{2+}\) and Zn\({}^{2+}\) posed the greatest risk for aquatic living organisms from an urban lake in China [12]. Moreover, heavy metals are non-degradable and accumulate in the organisms, thus persisting and accumulating throughout the food chain [2,4,13]. Pb\({}^{2+}\), for example, due to its environmental persistency, can impact the life course of individuals from the moment they are born. Pb\({}^{2+}\) exposure during childhood and throughout the years, not only impacts their biological systems, but also has long-term ramifications, such as lower cognitive function and downward social mobility [14,15]. In view of this, the dispersion of heavy metals throughout both terrestrial and aquatic ecosystems has raised many ecological and health concerns.