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Title: Development of Quaternized Biopolymeric Flocculants for Water Treatment
Authors: Khaira, Gurpreet Kaur
Supervisor: Ghosh, Moushumi
Keywords: Bioflocculant;antibacterial polymer;water borne pathogens;quaternization;cell permeability;toxicity;Biotechnology
Issue Date: 14-Nov-2014
Abstract: Providing safe drinking water is an important public health issue and recent studies have recognized commonly used flocculants and disinfectants responsible for unintended health hazards. An increased resistance of waterborne pathogens to synthetic biocides and environmental considerations underpin an urgency to develop strong, economically viable and ecofriendly replacements of conventional synthetic flocculants and disinfectants. Distinctive nature of microbial extracellular polymers containing amino groups can be explored in hope to obtain effective and safe substitute to chemical biocides. Although, many natural and synthetic water treatment agents are available in the market, but natural products are not as efficient as the semi-synthetic or synthetic compounds in terms of efficacy. Thus in the present study, an attempt was made to design a semi-synthetic flocculant-disinfectant replete with sustainability, cost effectiveness, biocompatibility, non-toxic polymers with high inactivation efficacy of waterborne pathogens. In an attempt to develop antibacterial polymer(s) with dual flocculant-disinfectant property, we chemically altered the surface properties of an amino sugar rich biopolymeric flocculant produced by Klebsiella terrigena. Chitosan, most extensively modified polymer, was used as reference compound due to its structural similarity to the bioflocculant. Alteration were brought about in the native biopolymers through quaternization, and the trimethyl biopolymeric derivatives (N,N,N trimethyl biopolymer and N,N,N trimethyl chitosan, abbreviated as TMB and TMC, respectively) were analyzed physically, chemically and for flocculating properties. TMB did not differ significantly (p<0.05) in either chemical, physical properties or flocculating ability when compared to its native counterpart. The antibacterial activity of water-soluble derivatives was investigated against six prevalent water borne-pathogens, viz. Salmonella typhimurium ATCC 25315, Shigella flexneri 2a, Aeromonas hydrophila ATCC 35654, Yersinia enterocolitica ATCC 9610, Listeria monocytogenes ATCC 19111 and Escherichia coli O157:H7 ATCC 32150. Results revealed an inactivation of 4 log CFU/ml of all water borne pathogens with TMB as compared to TMC which resulted in inactivation of 3 log CFU/ml, over a short contact time (30-60 minutes) and low dosage (30-90µg/ml) at ambient temperature. The biochemical and physiological insights on mode of action of quaternized derivatives suggested membrane damage by TMB to be the principal mechanism for inactivation against all the bacteria. In the Salmonella Ames assay, TMB failed to induce His+ revertants in a significant manner (p<0.05) indicating that TMB lacked mutagenic or carcinogenic potential. Further, study on mortality, gross toxic effects, behavioral changes and the hematological, histopathological and general examinations indicated no adverse effects in acute toxicity studies in Swiss albino mice fed with the quaternized biopolymer (140mg/Kg/bodyweight/day) over a period of 30 days. Overall the study suggested that TMB was tolerated well without any signs of toxicity and may have potential application as a safe, antimicrobial bioflocculant for both removing and inactivating water borne pathogens.
Description: Ph.D, BTD, Thesis
Appears in Collections:Doctoral Theses@DBT

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