Synthesis and application of antimicrobial poly(vinyl alcohol) electrospun nanofibers for water filtration

Abstract

This thesis deals with the fabrication, characterization, and evaluation antimicrobial and anti-biofouling activity of electrospun poly (vinyl alcohol) (PVA) nanofibers with quaternary ammonium compound (QAC) and PVA/poly acrylic acid (PAA) nanofibers with protease for applying in water filtration. BTEAC-PVA electrospun nanofibers was fabricated via co-electrospinning, and PVA/PAA-Cu(II) containing α-chymotrypsin was synthesized with soaking treatment after electrospinning. The synthesized nanofibers were characterized by various analytical techniques such as SEM, EDS, DSC, TGA, FTIR, and CFP. BTEAC-PVA nanofibers containing 2.6% BTEAC were fabricated to test the antibacterial and antiviral activities. For the BTEAC-PVA nanofibers, the bacterial reduction ratio increased with increasing contact time, demonstrating that BTEAC-PVA nanofibers successfully inhibited the growth of bacteria. In addition, the antiviral tests against viruses (bacteriophages MS2 and PhiX174) showed that the BTEAC-PVA nanofibers inactivated both MS2 and PhiX174. BTEAC-PVA deposited on GF membrane (BTEAC-PVA/GF ENMs) for increasing mechanical strength. BTEAC-PVA/GF ENMs were also examined water stability, flux, pore size, leaching, and D.magna toxicity that they are good candidate for environmental friendly micro-filter as water filter. After 10 ml filtration, 4.88 LRV (E. coli) and 5.75 LRV (S. aureus) was achieved using BTEAC-PVA/GF ENMs. Finally, 2.26 LRV (E. coli) and 3.29 LRV (S. aureus) was obtained after 500 ml filtrate volume with BTEAC-PVA/GF ENMs. The antibacterial water filtration test for river water were also performed that 67 CFU/mL (Total coliforms) in river water was removed all by BTEAC-PVA/GF ENMs during the filtration test. For anti-biofouling activity, deposited BTEAC-PVA on PC membrane (BTEAC-PVA/PC ENMs) could enhance the flux due to protect from biofouling of PC membrane with microorganism (K. pneumonia) solutions. Anti-biofouling effect was due to contact-dependent killing of sessile cells rather than reduction in the number of planktonic cells through biofouling resistance test. Antimicrobial mechanism of BTEAC-PVA nanofibers is damaging bacterial membrane observed by fluorescence microscopy and field emission scanning electron microscopy (FESEM) images. BTEAC-PVA/PC ENMs generally showed retaining antimicrobial activity over 6 cycles in regeneration study with bacteria, and mixed bacteria strain solution. PVA/PAA nanofibers were successfully coordinated/chelated with Cu(II), then immobilization of α-chymotrypsin. The α-chymotrypsin is a proteas that could inhibit 53.50% of P. aeruginosa and 35.53% of S. aureus biofilm formation and reduce 58.2 % of P. aeruginosa biofilm and 43.5% of S. aureus biofilm with a microtiter assay. The Cu(II) adsorption capacity of PVA/PAA nanofibers is 44.85 mg/g (initial Cu(II) concentration = 500 mg/L, reaction time = 24 h) then immobilized amount of α-chymotrypsin on PVA/PAA-Cu(II) nanofibers is 25.56 ± 2.72 mg/g. PVA/PAA-Cu(II) nanofibers containing α-chymotrypsin have a good performance of anti-biofouling by reducing sessile cells via degrade EPS, especially protein. The functionalized PVA nanofibers were applied as a water filter, and showed antibacterial and anti-biofouling performance with various tests including contact test, dynamic test, dead-end filtration test, and incubation test. In addition, this dissertation provides the possibility of eco-friendly approaches for the preparation of PVA based nanofibers containing QAC and protease, and their potential applications in water filtration.