Structural, antioxidant, antibacterial and biodegradation properties of rice straw xylan (native and modified) based biofilms

Abstract

Summary The present study involved valorisation of rice straw by conversion of its constituent polymer xylan and chemically modified xylans into biofilms. Hemicellulosic xylan (19.94%) extracted with 10% NaOH (85 °C, 2.6 h) was chemically modified to acetylated (AX) and carboxymethylated xylan (CMX). Biofilms were prepared by reaction of xylan/modified xylan (1% and 2%) with polyvinyl alcohol using eco‐friendly and cheap cross‐linker citric acid and glycerol as plasticiser. 2% xylan biofilms showed maximum inhibition (94.25%) of DPPH at 4 mg mL−1 which was due to large number of free ‐OH groups (highest intensity of ‐OH absorption bands in FT‐IR spectra). 2% CMX biofilms exhibited maximum antibacterial effectiveness with diameter of zone of inhibition 33.5 and 30.5 mm against Bacillus subtilis and Pseudomonas sp., respectively. This may be due to large number of undissociated COO− ions (citric acid) in CMX biofilms which was evident from lesser cross‐linking observed in their SEM images. 2% CMX biofilms also showed the highest biodegradation (86.5%) which may be attributed to formation of ether bonds along with ester bonds leading to their fast degradation. Owing to good bioactive properties of prepared biofilms, it was concluded that these can be appropriate material for food packaging by replacing synthetic plastics.

Valorization of Grain and Oil By-Products with Special Focus on Hemicellulose Modification

“…The study results indicated that the addition of CA not only acted as a plasticizer but also improved the flexibility and processability of the material by forming ester bonds with the hemicellulose chains. Kapil et al [ 95 ] chemically modified rice straw xylan into acetylated xylan (AX) and carboxymethylated xylan (CMX) and created bio-composite films with polyvinyl alcohol (PVA) and CA. The introduction of AX and CMX enhanced the mechanical strength of the bio-composite films.…”

“…However, high concentrations of AX and CMX could lead to uneven intermolecular cross-linking, reducing the elongation at break of the films. The acetylation process reduced the number of free hydroxyl groups, thereby decreasing the antioxidant activity [ 95 ]. This suggests the need to prepare different modified hemicellulose-based materials according to specific requirements.…”

“…For instance, acetylation improves meltability but reduces thermal stability [ 127 ]. The acetylation process also reduces the number of free hydroxyl groups, thereby decreasing the antioxidant activity of xylan [ 95 ]. The modification process typically requires expensive chemical reagents and specialized equipment, leading to high production costs for the modified materials.…”