1 Plant Archives Vol. 20, Supplement 2, 2020 pp. 4105-4108 e-ISSN:2581-6063 (online), ISSN:0972-5210 REMOVAL OF SOME HEAVY METAL FROM AQUEOUS SOLUTIONS BY LACTIC ACID BACTERIA (WHOLE BACTERIA AND BIOFILM) Srbeel Khalid Saheh 1 and Asmaa Sabah Ahmaed 2 1 Anbar Agriculture Directorate, Ministry of Agriculture, Iraq, 2 Department of Food Sciences, College of Agricultural Engineering Sciences, University of Baghdad, Iraq Abstract Leuconostoc mesetroides, Lactobacillus casei and Lactobacillus rhamnosus GG a lactic acid bacteria were evaluated for its ability to remove of cadmium (Cd), lead(Pb) and cobalt(Co) from aqueous solution. The efficiency of whole bacteria was Leuconostoc mesetroides Lactobacillus casei and Lactobacillus rhamnosus GG of Cd metal was 90.848, 83.452, 71.909%, while biofilm was 40.691, 37.131, 37.033%. As for Pb, the highest removal rate for whole bacteria and biofilm for Leuconostoc mesetroides isolation was 91.317% and 72.313% respectively and corresponded to the Co, where the highest removal whole bacteria was by Leuconostoc mesetroides isolation 77.165% As for biofilm it was higher for Lactobacillus casei isolation was 23.359% .Experimental results reveal that all the whole bacterial isolates have potential application for remove of Cd, Pb and Co from the biofilm. Keywords : Heavy metal, Lactic acid bacteria, Biofilm, Cd, Pb, Co. Introduction Soil and water pollution by toxic heavy metals and organic pollutants occurs as a result of human activities and has ecome a major concern in the environment and health. Many toxic minerals such as (lead, mercury, copper, cadmium, zinc, nickel, arsenic, etc.) are released directly and indirectly from wastewater and other human activities in the environment (Gupta and Diwan, 2017). Contaminants with heavy metals are not biodegradable and able to enter the food chain through bioaccumulation. Heavy metals play a role in mineral enzymes and affect membrane stability such as ketones and affect DNA and metabolic functions (Siddiquee et al., 2015, Dedykhina and Eroshin, 1991). When cadmium, lead and mercury in the environment rise, they become more toxic (Gadd, 1986). Heavy metals can be defined based on three different criteria that include density, atomic number or their chemical properties (Radogevic et al., 2007). It was mentioned that heavy metals can be defined as the density of minerals (5 g / cm 3 ), which is five times more dense than water (Yu, 2001). Minerals are classified as elements with an atomic number greater than 20 with the exception of alkali metals, alkaline earth, lanthanides and actinides Arora et al. (2008) reported that heavy metals have the ability to accumulate in different parts of the human part. Concentrations of heavy metals have the property of long-life biology and resistance to degradable processes and chemical toxicity appears in soluble water if minerals have high concentrations and enter the human body, so they absorb and bind to vital molecules such as proteins and DNA and interfere with their functions. Lead and cadmium are among the most abundant mineral elements. They are biologically non-essential and non-degradable and tend to accumulate in living organisms exposed to them. Exposure to lead causes a neurological imbalance in the blood, dysfunction of the heart, blood vessels, liver, kidneys, and reproductive disorders in a human body, especially young children(Kirillova, et al.,2017;Rossi.,2008). As for cadmium toxicity, it is primarily associated with renal, structural, and pulmonary disorders, hepatic, reproductive, and cardiovascular disorders (Bernard, 2008). The International Agency for Research on Cancer (IARC) has classified cadmium as a human carcinogen (Godt et al., 2006). Cobalt causes negative effects on the human body by increasing its levels as it affects the respiratory system when inhaled in high concentrations as it causes asthma, pneumonia, vomiting, vision and heart problems and when dealing with long periods causes an effect on the thyroid gland (Welton et al., 2007) In order to obtain safe removal of heavy metals, Bioremediation was directed to microbial removal, microorganisms have developed various techniques for bonding with minerals and thus disposa. The cells, response to microorganisms, whether they are bacteria, fungi or algae, to get rid of the trustworthy minerals of many shapes, either through the cell’s wall or biofilm formation Lactic acid bacteria a positive bacteria for the dye that is often bacillus, producing lactic acid as a major product of fermentation of carbohydrates (Axelsson, 2004) Therefore, the aim of this study was the susceptibility of some bacterial isolates producing lactic acid to produce the biofilm and studying the ability of these isolates toward Cd, Pb and Co by using whole bacterial cells and biofilm Materials and Methods Bacterial isolates Bacterial isolates produced lactic acid were obtained Leuconostoc mesetroides (Lm), Lactobacillus casei (Lc) and Lactobacillus rhamnosus GG(LGG) that cultivation in MRS broth media (10ml) at 37 o C for 48 h. Calculating bacterial numbers Bacterial numbers of isolates were counted according to the Macfarland method (Vandepitte et al., 2003 It used 10 8 cells/ml in subsequent experiments Investigation of biofilm production The Micro titer plate method(MTP) was used to investigate the production of biofilms by bacterial isolates under study, as the accurate calibration dishes containing 96 flat bottoms and the MRS culture medium used in the study and the aqueous solution of the violet crystal dye at 0.1%