Phytoextracts protect Saccharomyces cerevisiae from oxidative stress with simultaneous enhancement in bioremediation efficacy

Bioremediation efficacies are highly affected by abiotic stresses imparted by a verity of pollutants due to generation of reactive oxygen species (ROS). These stressed cells can be treated using natural or synthetic antioxidants. Such an approach could prove beneficial to bioremediation agents as the exogenously added antioxidant compounds would scavenge the generated free radicals. This would definitely lead to increased longevity of the involved organism and carry out superior treatments. In present study, Malachite Green (MG) was found to exert oxidative stress on Saccharomyces cerevisiae through generation ROS. A 2 h exposure of MG though achieved 99% decolourization, the cells revealed a significant decrease (97.8%) in colony forming units (CFU) upon further subculture. Natural antioxidants from Centella asiatica, Phyllanthus emblica, Asperagus racemosus and Tinospora cordifolia extracts, however, restored the CFU with a loss of only 16-33%. The MG stressed cells indicated an increase in ROS by 6.7 fold which was reduced to near normal due to augmentation with plant extracts. MG damaged the nuclear material up to 90% and inclusion of phytoextracts protected the cells revealing only 0-7% nuclear damage. Induction in apoptosis (92%) and necrosis (23%) in MG exposed cells was noted, while plant extracts augmentation reduced apoptosis to 15-49% and necrosis to 10-16%. Activities of antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase were significantly decreased in phyto-augmented cells when compared to MG stressed cells. Dye degrading enzymes, namely lignin peroxidase, laccase, NADH-DCIP reductase and MG reductase were found to show induction in activities during MG utilization. Since antioxidants from plant extracts could protect the cells form oxidative stress, they were used to treat MG for 20 continuous decolourization cycles. Augmentation of C. asiatica, P. emblica, A. racemosus and T. cordifolia extracts at 20th decolourization cycle revealed 75, 79, 74 and 93% superior decolorization efficacies as compared to unaugmented cells. These natural antioxidants to protect bioremediation agents form oxidative stress, thus concluded to show enhanced treatment.