N-Acetylmuramic Acid as a Fermentation-Level Metabolic Modulator of Bacterial Cellulose Biosynthesis and Material Properties

Abstract

Bacterial cellulose (BC) is a bacteria-derived biopolymer produced through aerobic fermentation and is valued for its high purity, biocompatibility, and mechanical strength, making it suitable for various biological and industrial applications. N-Acetylmuramic acid (MurNAc), a key component of bacterial peptidoglycan involved in cell wall recycling and metabolism, was investigated as a potential modulator of BC biosynthesis, a role that has not previously been explored in kombucha-based fermentation systems. This study examined the effects of MurNAc supplementation at concentrations of 0, 2, and 8 µg/mL on BC yield, tensile properties, surface wettability, and morphology under static kombucha fermentation conditions. BC pellicles were harvested, purified, dried, and analysed using dry-weight determination, tensile testing, water contact angle measurements, and scanning electron microscopy (SEM), with statistical comparisons performed using one-way ANOVA. MurNAc significantly reduced BC yield in a concentration-dependent manner, from 5.24 ± 0.99 g in the control to 1.25 ± 0.04 g and 1.10 ± 0.58 g at 2 and 8 µg/mL, respectively (p < 0.05). In contrast, tensile strength increased with MurNAc concentration, from 1.11 ± 0.21 MPa in the control to 1.35 ± 0.54 MPa at 2 µg/mL and 3.32 ± 0.24 MPa at 8 µg/mL, whereas strain at break decreased from 14.31 ± 0.93% to 11.59 ± 4.26% and 5.77 ± 0.27%, respectively. Surface wettability exhibited a non-monotonic response, with the water contact angle increasing from 27.19 ± 1.22° in the control to 45.34 ± 0.58° at 2 µg/mL before decreasing to 26.98 ± 3.55° at 8 µg/mL. SEM analysis revealed that MurNAc progressively altered the BC microstructure, from a relatively dense and interconnected fibrillar network in the control to increased pore spacing at 2 µg/mL and a disrupted, aggregated fibrillar architecture at 8 µg/mL. These findings demonstrate that MurNAc modulates BC biosynthesis and physicochemical properties in a concentration-dependent manner, substantially reducing cellulose yield while altering its mechanical performance, surface wettability, and fibrillar organization.