# Enhancing Paper’s Mechanical Strength and Antibacterial Properties through a Biopolymer-Based Coating

## TL;DR

This paper shows how a biopolymer coating made from soybean flour and cellulose can strengthen paper and reduce bacteria, making it useful for packaging.

## Contribution

A new biopolymer coating using citric acid-modified soybean flour and CMC is developed to enhance paper's mechanical and antibacterial properties.

## Key findings

- The coating improved paper's tensile strength by 61.8%.
- It reduced bacterial colonies by 84–89% against Escherichia coli.
- The optimal coating formulation was a 50:50 blend of SBFC and CMC.

## Abstract

This study presents a sustainable approach to improving
the antibacterial
and mechanical properties of paper through the application of a biopolymer-based
coating derived from citric acid-modified soybean flour (SBFC) and
carboxymethyl cellulose (CMC). The SBFC was synthesized via thermal
cross-linking between citric acid and defatted soybean flour under
optimized conditions (140 °C for 2 h, with Na2HPO4 as a catalyst), facilitating ester and amide bond formation
that was confirmed via FTIR spectroscopy. Aqueous solutions of SBFC
were subsequently blended with CMC at varying ratios, and a 50:50
formulation was optimized for the best performance of dispersion stability
and coating performance. The final SBFC/CMC coating exhibited a 61.8%
improvement in tensile strength compared to uncoated paper. Antibacterial
activity was evaluated using Escherichia coli ATCC 25922 as a model Gram-negative bacterium, with bacterial reduction
confirmed through CFU-based plate counts. The coating achieved a log10 reduction of 1.2–1.7 relative to that of the controls,
corresponding to an 84–89% reduction in viable bacterial colonies.
While testing was limited to a single bacterial strain, the results
demonstrate promising antibacterial performance. This work highlights
the potential of citric-acid-modified biopolymer coatings as multifunctional
additives for improving the performance and hygiene properties of
paper substrates, particularly in packaging applications.