Ratan Kumar Basak

Improvement in mechanical properties of jute fibres through mild alkali treatment as demonstrated by utilisation of the Weibull distribution model

Chemically modified jute fibres are potentially useful as natural reinforcement in composite materials. Jute fibres were treated with 0.25%-1.0% sodium hydroxide (NaOH) solution for 0.5-48 h. The hydrophilicity, surface morphology, crystallinity index, thermal and mechanical characteristics of untreated and alkali treated fibres were studied.The two-parameter Weibull distribution model was applied to deal with the variation in mechanical properties of the natural fibres. Alkali treatment enhanced the tensile strength and elongation at break by 82% and 45%, respectively but decreased the hydrophilicity by 50.5% and the diameter of the fibres by 37%.

Composition analysis and material characterization of an emulsifying extracellular polysaccharide (EPS) produced by Bacillus megaterium RB-05: a hydrodynamic sediment-attached isolate of freshwater origin.

Aims:  This work was aimed to isolate, purify and characterize an extracellular polysaccharide (EPS) produced by a freshwater dynamic sediment‐attached micro‐organism, Bacillus megaterium RB‐05, and study its emulsifying potential in different hydrocarbon media.

Low fucose containing bacterial polysaccharide facilitate mitochondria-dependent ROS-induced apoptosis of human lung epithelial carcinoma via controlled regulation of MAPKs-mediated Nrf2/Keap1 homeostasis signaling

Reactive oxygen species (ROS), the key mediators of cellular oxidative stress and redox dysregulation involved in cancer initiation and progression, have recently emerged as promising targets for anticancer drug discovery. Continuous free radical assault upsets homeostasis in cellular redox system and regulates the associated signaling pathways to mediate stress‐induced cell death. This study investigates the dose‐specific pro‐oxidative behavior of a bacterial fucose polysaccharide, which attenuated proliferation of different cancer cells. In the fermentation process, Bacillus megaterium RB‐05 [GenBank Accession Number HM371417] was found to biosynthesize a polysaccharide with low‐fucose content (4.9%), which conferred the maximum anti‐proliferative activity (750 µg/mL) against human lung cancer epithelial cells (A549) during preliminary screening. Structural elucidation and morphological characterization of the duly purified polysaccharide was done using HPLC, GC‐MS, 1H/13C NMR, and microscopy. The polysaccharide exhibited concentration‐ and time‐dependent anti‐proliferative effects against A549 cells by inducing intracellular ROS level and regulating the mitochondrial membrane‐permeability following the apoptotic pathway. This process encompasses activation of caspase‐8/9/3/7, increase in the ratio of Bax/Bcl2 ratio, translocation of Bcl2‐associated X protein (Bax) and cytochrome c, decrease in expression of anti‐apoptotic members of Bcl2 family, and phosphorylation of mitogen activated protein kinases (MAPKs). Apoptosis was attenuated upon pretreatment with specific caspase‐inhibitors. Simultaneously, during apoptosis, the ROS‐mediated stress as well as activated MAPKs triggered nuclear translocation of transcription factors like nuclear factor (erythroid‐derived)‐like 2 (Nrf2) and promoted further transcription of downstream cytoprotective genes, which somehow perturbed the chemotherapeutic efficacy of the polysaccharide, although using CuPP, a chemical inhibitor of HO‐1, apoptosis increased significantly (P < 0.05).

Characterization and emulsifying property of a carbohydrate polymer produced by Bacillus pumilus UW-02 isolated from waste water irrigated agricultural soil

Bacillus pumilus UW-02, an isolate from agricultural soil irrigated with waste water was found to produce a carbohydrate polymer in the form of extracellular polysaccharide (EPS) in glucose mineral salts medium (GMSM). The recovery rates of EPS by ion-exchange and gel filtration chromatography were around 63% and 90%, respectively. As evident from HPLC and FT-IR analyses, the EPS was found to be a heteropolymer consisting glucose, mannose, xylose, arabinose, and N-acetyl glucosamine as monomer units. Different oligosaccharide combinations namely hexose(4), hexose(6) pentose(1) and hexose(10) pentose(1) are obtained after partial hydrolysis of EPS using MALDI-ToF-MS. Electron micrographs portrayed the intense affinity of the EPS molecules for each other, thereby justifying its viscosifying and thickening properties. The EPS with an average molecular weight of 218 kDa and thermal stability up to 180 °C showed pseudoplastic rheology and significant emulsifying activities.