Combining Microbial Cellulose with FeSO₄ and FeCl₂ by Ex Situ and In Situ Methods

Environmentally sustainable methods for producing flexible electronics, such as paper-based energy harvesters in nanogenerators, are a major objective in materials science. In this frame, the present study investigated two different Komagataeibacter sp. strains (K2G30 and K2G44), never tested as biocatalysts for the production of bacterial cellulose (BC) functionalized with iron particles to provide potential electrical conductivity. Two functionalization strategies (ex situ and in situ) were evaluated using two iron compounds FeCl₂ and FeSO₄, individually and in combination (up to 0.1% w/v), to assess efficiency and feasibility. In addition, a Design of Experiment approach was implemented to calculate quantitative mathematical models to correlate the functionalization methods with the iron amount in the BC. Among the tested conditions, BC produced by strain K2G44 using the ex situ method with FeCl₂ showed the most promising results, achieving the highest iron content (~37% atomic weight) with a highly homogeneous dispersion of iron nanoparticles. Moreover, the in situ BC functionalization using FeSO₄ led to the formation of iron gluconate. FeSO₄ alone significantly enhanced BC production in the in situ process, with yields of 2.62 ± 0.15 g/L for K2G30 and 2.05 ± 0.09 g/L for K2G44.