Penicillium sp. increases total arsenic concentration in rice grains

Bioremediation of soils contaminated with arsenic (As) applying microorganisms has been an issue of interest for researchers because it is environment friendly and cost effective1. Some fungi are capable of accumulate or volatilize arsenic2. Among the mechanisms involved in accumulation and volatilization of As, main microbial process are uptake/efflux, oxidation/reduction, methylation/demethylation and complexation with Cys-rich peptide3. In matter of remediation of soils destined to rice cultivation, volatilization and/or methylation of arsenic due to fungi activity are desirable effects, once toxicity of methylated species of arsenic is lower than toxicity of inorganic arsenic. Further, at the present study, we cultivated rice in soil containing Penicillium sp., aiming to investigate if these fungi volatilize or methylate arsenic. For the cultivation, we prepare four group of soils: (a) group 1 (control group) – soil containing agar and As V; (b) group 2 – soil containing agar, Penicillium sp. and 5 mg kg-1 of As V; (c) group 3 (control group) – soil containing agar, and (d) group 4 – soil containing agar and Penicillium sp. After growth, grains were collected, milled and digested by microwave assisted digestion (Ethos Easy, Milestone, Italy). After digestion, determination of total arsenic was carried out by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) (ICP-MS 7900, Agilent, Japan). Results were statistically compared (t-test, 95% confidence interval). Group 4 presented total arsenic 28% higher than the control (group 3). Since organic arsenic species usually translocate efficiently to grains than inorganic arsenic, we infer that methylation might occurs in soil due to fungi action, increasing the total concentration of As in grains. Aiming to confirm our finds, our group is planning a future work, where speciation analysis will be carried out.