Properties of optimised bacterial cellulose via automated media optimisation screening system / Nuraqilah Hishammuddin

Bacterial cellulose (BC) pellicle produced from the fermentation process of Acetobacter xylinum has many advantages such as high-water holding capacity, good mechanical strength, high porosity, and high purity compared to plant cellulose. However, one of the BC application problems in the industry is its low bio-cellulose productivity and high-cost production. An optimized nutrient is vital for higher BC production, hence significant variables comprising of nitrogen source, glucose, coconut water and buffering effect could modulate the efficacy of BC. Optical density at 385 nm wavelength (OD385) was used as a proxy of BC production dynamics measurement to establish the nutrient screening as a high-throughput system, namely automated media optimization system (AMOS). In this study, the capability of AMOS for optimization of BC production in static fermentation process investigated. The screen designed to optimize three nutrients via the Response Surface Methodology (RSM) experimental design that establish 20 media formulations matrix for BC cultivation (150μl microplate-based miniature-scale cultivation system). Data obtained from experiment analysed with RSM of MINITAB Statistical Software (Version 18) whereby optimum BC production was determined and designated as Model (M). Medium formulation no. 8 and 16 (from the 20 media formulation) yielded the highest endpoint OD385 of 1.319±0.009 and 1.345 ±0.023 respectively, and both formulations were predesignated as medium C8 and C16 respectively for subsequent experiments. Reproducibility assessment of these media (150ml scale experiments) was in concordance with miniature scale data. BC film was then characterized morphologically by FESEM and SEM, structurally by XRD, FTIR and mechanically by Tensile machine. The analysis reveals that with optimal nutrient of media condition, morphological, mechanical strength and thermal stability of the processed films are also improved. It found that the bio-cellulose dry weight was at the greatest in C8 (acetate buffer) of 5.66 g/L while the dry weight derived from Control and Hestrin and Schramm (HS) are 2.72 g/L and 2.56 /L respectively. This shows that nutrient concentration and buffering capacity added has the most significant influence and may further improve the A. xylinum growth performance on its cellulose production in statically fermentation. Thus, the optimum nutrient formulation yielded promising results to overcome low BC productivity in static cultivation.