Development of antibacterial biocomposites reinforced with cellulose nanocrystals derived from banana pseudostem

Enzyme-based green synthesis, characterisation, and toxicity studies of cellulose nanocrystals/fibres produced from the Vetiveria zizanioides roots agro-waste

Vetiver zizanioides roots are considered the most useful part of the plant. It is widely used to extract oil. The aromatic oil is used in perfumery, food-flavouring and cosmetic industries. However, presently, there are no reports available for the usage of vetiver roots agro-waste after oil extraction in nano-based products. Considering the concept of value-added products and green-chemistry approaches, synthesising cellulose nanoparticles (CNPs) using enzymatic treatment from agro-waste has emerged as a viable option. CNP's non-toxicity, biodegradability, and biocompatibility have sparked the industry's interest in its production. Therefore, in the present study, 3 enzymes, cellulase, pectinase, and viscozymes, were used for the green synthesis of CNP. The characterisation of CNP was done using techniques like DLS, FTIR, TEM, SEM, AFM, and TG/DTG, and cytotoxicity of CNP was studied in human skin cell-line (HaCaT) using MTT assay. Results show that CNPs synthesised using viscozyme and pectinase were of crystalline nature (2.0-3.0 nm) and cellulase were of fibres (40-60 nm). The FTIR confirmed that CNPs were devoid of lignin/hemicellulose. The AFM pictures revealed thick and thin nanoparticles with a variety of morphologies. The thermal stability of cellulose was higher compared to CNP. All the synthesised CNPs were crystaline, with a 60-70% crystallinity index. Furthermore, CNP did not show cytotoxic effect on HaCaT cells upto 500 µg/mL concentrations. In conclusion, pectinase and viscosyme may be used for synthesing cellulose-nanocrystals and cellulase enzyme for cellulose-nanofibers from the vetiver roots agro-waste. The findings revealed that Vetiveria zizanioides agro-waste-derived CNP is a sustainable material that can be used as a reinforcing agent/nanocarrier in textile and drug-delivery systems.

Recent advances in cellulose nanocrystals-based antimicrobial agents

Over the past five years, there has been growing interest in the design of modified cellulose nanocrystals (CNCs) as nanoscale antimicrobial agents in potential end-user applications such as food preservation/packaging, additive manufacturing, biomedical and water purification. The interest of applying CNCs-based antimicrobial agents arise due to their abilities to be derived from renewable bioresources and their excellent physicochemical properties including rod-like morphologies, large specific surface area, low toxicity, biocompatibility, biodegradability and sustainability. The presence of ample surface hydroxyl groups further allows easy chemical surface modifications for the design of advanced functional CNCs-based antimicrobial materials. Furthermore, CNCs are used to support antimicrobial agents that are subjected to instability issues. The current review summarizes recent progress in CNC-inorganic hybrid-based materials (Ag and Zn nanoparticles, other metal/metal oxide) and CNC-organic hybrid-based materials (polymers, chitosan, simple organic molecules). It focuses on their design, syntheses and applications with a brief discussion on their probable modes of antimicrobial action whereby the roles of CNCs and/or the antimicrobial agents are highlighted.

Preparation of chitosan/gelatin-based functional films integrated with carbon dots from banana peel for active packaging application

Carbon dots (CDs) were manufactured with banana peels using a hydrothermal method (200 °C for 6 h). The synthesized CDs were spherical particles with a size of 1-3 nm having carboxyl groups and amine groups on the surface. CDs have been impregnated into chitosan/gelatin films to synthesize multifunctional packaging films. The composite film showed a slight decrease in transparency but a significant increase in UV protection properties. The fabricated film displayed strong antioxidant efficacy showing >74 % DPPH and 99 % ABTS radical scavenging potential. The film also unveiled substantial antibacterial activity against the foodborne pathogenic bacteria, Listeria monocytogenes, fully eliminating the growth of these bacteria within 6 h of exposure. The chitosan/gelatin film containing CD was used for minced meat packaging, and the film delayed bacterial growth (< 1 Log CFU/g after 24 h) and maintained the meat color even after 24 h of storage at 20 °C. The CD-added chitosan/gelatin functional film has a high probability of application in active food packaging, especially for extending the shelf life of packaged meat and maintaining its aesthetic quality.

Banana biomass waste: A prospective nanocellulose source and its potential application in food industry - A review

Bananas are among the most produced and consumed fruit all over the world. However, a vast amount of banana biomass is generated because banana trees bear fruit only once in their lifetime. This massive amount of biomass waste is either disposed of in agricultural fields, combusted, or dumped at plantations, thus posing environmental concerns. Nanocellulose (NC) extraction from this source can be one approach to improve the value of banana biomass. Owing to its superb properties, such as high surface area and aspect ratio, good tensile strength, and high thermal stability, this has facilitated nanocellulose application in the food industry either as a functional ingredient, an additive or in food packaging. In this review, two different applications of banana biomass NC were identified: (i) food packaging and (ii) food stabilizers. Relevant publications were reviewed, focusing on the nanocellulose extraction from several banana biomass applications as food additives, as well as on the safety and regulatory aspects. Ultimately, further research is required to prompt a perspicuous conclusion about banana biomass NC safety, its potential hazards in food applications, as well as its validated standards for future commercialization.