Comprehensive Characterisation of the Morphological, Thermal and Kinetic Degradation Properties of Gluconacetobacter xylinus synthesised Bacterial Nanocellulose

ABSTRACT

Microbial-assisted synthesis can advance nanocellulose production, while addressing the economics and environmental friendliness of conventional techniques. Bacterial nanocellulose (BNC) is a linear exopolysaccharide with 3-D structures and nanofibril networks synthesized by various bacteria. The physical, chemical and mechanical properties of BNC have been characterized for various applications. However, limited knowledge of the thermal degradation and kinetic properties of BNC currently hampers its utilization as renewable biopolymers as heat, temperature, and heating rates influence life span and future applications. Therefore, this study examines the thermal, chemical, morphological, microstructure, and kinetic properties of Gluconacetobacter xylinus synthesized BNC through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and isoconversional Ozawa–Flynn–Wall (OFW) kinetic modeling. The SEM results showed that BNC has a highly dense fibril structure with overlapping knots, which denotes a high surface area, porosity and crystallinity, whereas EDX revealed C, O, and Na. TGA revealed BNC undergoes three-stage thermal degradation with mass loss of 53.57% and residual mass of 46.43% on average. Kinetic modeling revealed the average activation energy (E_a = 59.39 kJ/mol) and pre-exponential factor (k_o = 1.62 × 10¹⁰ min⁻¹) for BNC indicating high thermal reactivity. Thus, G. xylinus- synthesized BNC has potential for many applications in the future.

摘要

微生物辅助合成可以促进纳米纤维素的生产，同时解决传统技术的经济性和环境友好性. 细菌纳米纤维素（BNC）是由多种细菌合成的具有三维结构和纳米纤维网络的线性胞外多糖. BNC的物理、化学和机械性能已在各种应用中得到表征. 然而，有限的知识热降解和动力学性质的BNC目前阻碍了其作为可再生生物聚合物的利用，因为热量，温度和加热率影响寿命和未来的应用. 因此，本研究通过热重分析（TGA）、扫描电子显微镜（SEM）、能量色散X射线（EDX）和等转化率Ozawa-Flynn-Wall（OFW）动力学模型研究了葡萄糖酸杆菌合成BNC的热、化学、形态、微观结构和动力学性质. 扫描电镜（SEM）结果表明，BNC具有高度致密的纤维结构 和重叠的节，这表明BNC具有较高的比表面积、孔隙率和结晶度，而EDX显示C、O和Na. TGA分析表明，BNC经历了三个阶段的热降解FF0C质量损失为53.57%，平均残余质量为46.43%. 动力学模型显示BNC的平均活化能（Ea=59.39kJ/mol）和指数前因子（ko=1.62×1010min-1）表明其具有较高的热反应活性. 因此，木霉合成的BNC具有广阔的应用前景.

KEYWORDS:

• Thermogravimetry
• kinetics
• bacterial nanocellulose
• Gluconacetobacter xylinus

关键词:

• 热重分析法
• 动力学
• 细菌纳米纤维素
• 木葡糖酸杆菌

Acknowledgments

The technical assistance of the Hydrogen and Fuel Cell Laboratory, Institute of Future Energy, and School of Chemical & Energy Engineering, and the University-Industry Research Laboratory, all at Universiti Teknologi Malaysia (Skudai Campus), are gratefully acknowledged.