Enzymatic hydrolysis of biologically pretreated sorghum husk for bioethanol production

Biological pretreatment of lignocellulosic biomass is considered to be energy-efficient and cost-effective. In the present study, sorghum husk was biologically pretreated with a white-rot fungus Phanerochaete chrysosporium (MTCC 4955) under submerged static condition. Ligninolytic enzymes like lignin peroxidase (0.843 U/mL) and manganese peroxidase (0.389 U/mL) played an important role in the biological pretreatment of sorghum husk. Activities of different hydrolytic enzymes such as endoglucanase (57.25 U/mL), exoglucanase (4.76 U/mL), filter paperase (0.580 U/mL), glucoamylase (153.38 U/mL), and xylanase (88.14 U/mL) during biological pretreatment of sorghum husk by P. chrysosporium were evaluated. Enzymatic hydrolysis of untreated sorghum husk and biologically pretreated sorghum husk produced 20.07 and 103.0 mg/g reducing sugars, respectively. This result showed a significant increase in reducing sugar production in the biologically pretreated sorghum husk as compared to its untreated counterpart. Biologically pretreated sorghum husk hydrolysate was further fermented for 48 h using Saccharomyces cerevisiae (KCTC 7296), Pachysolen tannophilus (MTCC 1077), and their co-culture resulting in ethanol yields of 2.113, 1.095, and 2.348%, respectively. The surface characteristics of the substrate were evaluated after the delignification and hydrolysis, using FTIR, XRD, and SEM, confirming the effectiveness of the biological pretreatment process

Polyherbal decoction modulates redox homeostasis during Malachite green induced metabolic stress in Saccharomyces cerevisiae

Malachite green (MG) is aquatic pollutant that induces oxidative stress when comes in contact with the living organisms. In Saccharomyces cerevisiae, MG produces intracellular reactive oxygen species (ROS) and these ROS disturb redox homeostasis and cellular functions leading to early cell death. Exogenous supply of natural antioxidants containing polyherbal decoction may play a crucial role in re-establishment of redox homeostasis by ensuring the cell survival. Exposure of MG to Saccharomyces cerevisiae resulted in a significant decrease (97.8%) in colony forming units (CFU). An Ayurvedic polyherbal formulation ‘Vayasthapana Rasayana’ (VR) which contains natural antioxidants from plants viz. Terminalia chebula, Clitoria ternatea, Boerhaavia diffusa, Centella asiatica, Phyllanthus emblica, Asparagus racemossus and Tinospora cordifolia at 1.0 mg/mL concentration could arrest the oxidative stress during MG exposure. Levels of ROS elevated up to 67.3% on MG exposure; while VR supplementation reduced it by 54.7%. MG induced cellular apoptosis in 38% and necrosis in 27% cells, while VR augmentation reduced it to 8%. Activities of antioxidant enzymes like catalase, superoxide dismutase and glutathione peroxidase in MG exposed cells were induced by 408, 144 and 140%, respectively, whereas, VR supplementation lowered the expressions to 102, 57 and 111%, respectively. Induction in caspases 3/7 activity was also found to be reduced by 65.39% after VR augmentation. Similarly, VR modulated activities of oxido-reductases like lignin peroxidase, laccase, NADH-DCIP reductase and MG reductase. VR supplementation also maintained the MG utilization potential of S. cerevisiae up to 20th exposure cycle which was otherwise arrested to 8th cycle. The treatment also decreased the ROS accumulation and nuclear damage, restoring the cell viability up to 94% and retained normal growth dynamics. Thus, VR supplementation could significantly decrease oxidative stress, enhance cell viability and ultimately protect the dying S. cerevisiae cells during MG exposure

Phytoextracts protect <i>Saccharomyces cerevisiae</i> from oxidative stress with simultaneous enhancement in bioremediation efficacy

469-478Bioremediation 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