Toxicological evaluation of the microbiologically treated sugarcane vinasse using the caco-2 cell line and wheat seeds as bioindicators

Abstract

Microbiological processes fungus-based has been reported as an effective and eco-friendliest for conditioning of sugarcane vinasse. Certainly, we demonstrated the potential of a native fungus identified as Aspergillus sp. V1 to neutralize vinasse and remove about 60% of the biodegradable organic matter at 12thdays of treatment. However, toxicity studies are usually required in order to determine the effectiveness of the bioprocesses applied to industrial waste materials. To this end, diverse organisms and cell lines can be used as possiblebioindicators. Interestingly, the response to toxicity levels of a waste was found to be largely dependent on the organism used. In the present work, it was conducted a toxicological evaluation of a local vinasse sample, both raw as treated with Aspergillus sp. V1 for 12 days, using Caco-2 cells and seeds of Triticum aestivum L. (wheat) as bioindicators. Caco-2 cells were incubated for 3 h with 200 µl of vinasse raw or treated. Cells were rinsed and incubated for 3 h with the MTT [(4,5-Dimethylthiazol-2yl)-2,5-diphenyl-tetrazolium bromide], which is converted to the insoluble purple formazan in viable cells. Formazan crystals formed were solubilized with dimethyl sulfide, and the absorbance was measured at 570 nm in order to determine the percent viability. Regarding the wheat seeds, these were placed in Petri dishes containing sterile filter paper (Whatman No. 1) with 30 g of a natural garden soil moistened with 10 mL of vinasse raw or treated. After 7 days of incubation at 25°C under controlled environmental conditions, it was determined the percent germination of seeds. Experimental results demonstrated only a 13% of viability for Caco-2 cells exposed to raw vinasse. This percent increased until 49% when the cells were exposed to the vinasse treated with Aspergillus sp. V1, a value increased 3-fold compared to raw effluent. Regarding the Triticum aestivum L., raw vinasse completely inhibited the germination of the seeds. However, application of treated effluent was consistent with an average germination percentage of 60%. It from the current study it was concluded that both bioindicators could be successfully used to predict potential toxic effects of sugarcane vinasse.