Biodegradability of bacterial cellulose polymer below the soil and its effects on soil bacteria diversity

Abstract

The increasing demand for sustainable materials has led to a surge in research on biodegradable polymers. This study evaluated the weight and visual changes of bacterial cellulose (BC) polymers and nylon membranes during an eight-week biodegradation study below soil. Scanning electron microscope (SEM) images were taken to investigate morphological changes from decomposition. Changes in soil microbial communities and the relationship between microbial abundance and BC biodegradation were investigated. BC was produced from the fermentation of coffee kombucha using 15 % d-dextrose C6H12O6 (DE) as the nutrient carbohydrate substrate. BCs were purified with 0.5 mol/L aqueous NaOH solution and 1.5 % (v/v) aqueous NaOCl and then freeze-dried. The biodegradation study was conducted using seedling pots and nylon membrane filters inside a greenhouse over eight weeks, with sample points taken at various intervals. Soil characteristics such as pH, nutrient content, texture, organic matter, and soil moisture were analyzed. Results showed that BC polymers underwent significant weight losses and visual decomposition, while nylon membranes did not show any weight or visual losses. Approximately 75 % of the BC polymers were decomposed by the end of the study. Fatty acid methyl ester (FAMEs) analysis showed increased microbial absolute abundance (nmol/g) for BC treatments over biodegradation time. FAMEs principal component analysis (PCA) ordination plots showed the relative abundance of fungi increased in BC microbial communities suggesting fungi's attraction to cellulose. Soil bacterial DNA analysis revealed the dominance of Proteobacteria for all treatments. PCA plots and Faith-pd index Alpha Diversity results showed significant bacterial community variations for week 2 of the biodegradation study compared to the other weeks. Adonis microbial community Beta Diversity analysis showed significant differences between treatments (p = 0.001). PCA plots also showed a slight differentiation of the bacterial communities with BC compared to bacterial communities with nylon and soil (control). This study confirms that BC is easily decomposed in soil and that its biodegradability is likely driven by fungal communities.