Antimicrobial/Antimold Polymer-Grafted Starches for Recycled Cellulose Fibers

Abstract

In this work, an antimicrobial guanidine polymer (PHGH) was grafted onto starch as a carrier to form branched or grafted chains along the starch backbone. This grafting improved the antimicrobial properties and the adsorption of the starch on recycled cellulose fibers. Similar work was also conducted on bleached sulfite fibers for comparison. The results showed that the starch, grafted with 12 wt% PHGH, adsorbed more on recycled fibers than on sulfite fibers. By applying the antimicrobial-modified starch to recycled or sulfite pulps up to 20 mg/g, both antimicrobial and antimold performances of the papers were improved substantially. Additionally, the PHGH-modified starch increased the tensile index of papers, but decreased the tear index slightly. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to investigate the morphologic changes of Escherichia coli bacteria and Chaetomium globosum fungi upon exposure to the PHGH-modified starch, thus demonstrating that the antimicrobial mechanism is based on the damage of bacterial membrane.

Coating PHGH-Modified Starch on Papers to Induce Antimicrobial Properties

“…The results from previous work by the authors showed that the grafting percentages of PHGH for different starches ranged from 12 to 20 wt.% (Ziaee et al 2010). The first layer (i.e., clay/latex mixture) had an average basis weight of 5.9 g/m 2 , whereas the second layer (PHGH-modified starch) varied from 1.9 g/m 2 to 2.8 g/m 2 .…”

“…The antibacterial activities were tested against Gram-negative Escherichia coli (E. coli, ATCC 11229) bacteria based on adopting the American type culture collection (ATCC-100) method (Ziaee et al 2010).…”

“…Fresh and treated E. coli solutions were deposited onto a silicon wafer (University Wafer, Boston, MA, United States) and air-dried. AFM images were obtained in tapping mode using a silica probe (NP-S20, Veeco Instruments) with settings of 512 pixels/line and a 1-Hz scan rate (Ziaee et al 2010). The AFM sample preparation procedure most probably led to killing E. coli cells as cells were dried after treating with distilled deionized water, implying that the AFM analysis was conducted on dead fresh and treated E. coli cells in this work.…”

“…Initially, unmodified and modified C. globosum were fixed in 6% glutaraldehyde for 2 h prior to washing with sodium cacodylate buffer. Then, the samples were fixed in 1% OsO 4 for 1 h, washed again with the same buffer solution, dehydrated in ethanol, dried, and coated with gold (Ziaee et al 2010).…”

“…The main focus of this paper was on the antimicrobial and antifungal properties of the paper coating. Although some aspects of PHGH-modified starch were studied in the past (Ziaee et al 2010), the main novelties of the present work are the studies on the antimold properties of this polymer and on the impact using this polymer on coating papers.…”