CR (VI) REMOVAL COMPARATIVE EVALUATION BY USING FUNGAL MIXED CULTURES

VILLEGAS LB; CASTRO MF; BAZÁN C

San Miguel de Tucumán

Congreso; SAMIGE 2017; 2017

Sociedad Argentina de Microbiología General

The use of resistant microbial consortia in heavy metals bioremediation processes has clear advantages over the application of pure cultures. In previous studies three Cr (VI) resistant strains were isolated from Chorrillos River, San Luis, Argentina: Candida sp. (C), Wickerhamomyces sp. (W) and Trichoderma sp. (T) these strains removed high Cr (VI) concentrations in liquid monocultures. The objective of this work was to evaluate and compare the growth and Cr (VI) speci!c removal capacity of mixed cultures. Interaction tests were realized in EG agar medium (g L-1: glucose, 10; K2HPO4, 0.125; KH2PO4, 0.125; MgSO4,0.1; yeast extract, 1 and agar, 15) to check the antagonism between selected fungi in the presence or the absence of Cr (VI). 106 yeast cells or !lamentous fungus spores mL-1 (to !nal concentration) were inoculated in 50 mL of EG liquid medium supplemented with the mentioned above Cr(VI) concentrations during 120h, at 30°C and 200 rpm. A biotic control (BC), under the same Conditions, was evaluated. Every 24 hours, growth was evaluated by dry weight, Cr (VI) removal by colorimetric method of 1, 5-Diphenylcarbazide. Total chromium concentration in supernatants was analyzed by Atomic absorption spectroscopy (Shimadzu, AA-6800) at 24, 72 and 120h. An inhibitory effect between Candida sp.and Trichoderma sp. was observed in plate interaction assay; this was only observed in the presence of 75 and 100 mgL-1 Cr (VI). This test was repeated in liquid medium, and Trichoderma sp. spores germination inhibition was observed under all concentrations of Cr (VI) used in presence of Candida sp. Basedon these results two double mixed cultures were studied: C-W and T-W. The microbial growth in mixed cultures was signi!cantly affected under all Cr (VI) concentrations, a decrease of 50-60% in C-W and 70-80% in W-T were observed respect to BC. C-W showed the higher Cr (VI) removal than T-W under all concentrations studied to shorter times. These values were 88.8% ± 0.37; 74.50%±0.88; 57.66% ±2.05 and 46.8% ± 3.88 at 25, 50, 75 and 100 mgL-1 Cr(VI) respectively. No signi!cant differences were observed in the total chromium removal between the different times in all concentrations. Total chromium for C-W decreased by 11.3% to 26.8% with 50 and 25 mg L-1 Cr (VI) at 72 h respectivelyand with 75 and 100 mgL-1 remained constant. On the other hand, T-W removed 15.6 to 20.8% with 75 and 100mgL-1 respectively and with 25 and 50 mgL-1 the total chromium concentration continued constant. The C-W double mixed culture was the most ef!cient to remove Cr (VI). These are promising results and it is expected, in future studies, to optimizing the culture medium to achieve Cr (VI) removalprocess more effective, eficient and economic.