Changed Characteristics of Bacterial Cellulose Due to Its In Situ Biosynthesis as a Part of Composite Materials

In recent years, the sustained and even increasing interest in the development and application of novel composite materials based on the polysaccharide bacterial cellulose (BC) has been driven by the accumulation of experimental data and the emergence of analytical reviews that narratively summarize these findings. This review presents a comparative and critical analysis of various approaches to the fabrication of BC-based composites. Among them, in situ biosynthesis is highlighted as the most promising strategy. In this approach, different additives are introduced directly into the culture medium of BC-producing microorganisms, enabling the formation of materials with different mechanical and physicochemical properties. Such a method also allows imparting to the composites a range of properties that BC itself does not possess, including antibacterial and enzymatic activity, as well as electrical conductivity. During the so-called “cell weaving” stage, performed by BC-producing microorganisms, diverse substances and microorganisms can be incorporated into the cultivation medium. By varying the concentrations of the introduced compounds, their ratios to the synthesized BC, and by employing different BC-producing strains and substrates, it becomes possible to regulate the characteristics of the resulting composites. Special attention is given to the role of various polysaccharides that are either introduced into the medium during BC biosynthesis or co-synthesized alongside BC within the same environment. Depending on the mode of incorporation of these additional polysaccharides, the resulting materials demonstrate variations in Young’s modulus and tensile strength. Nevertheless, they almost invariably exhibit a decreased degree of BC crystallinity within the composite structure and an enhanced water absorption capacity compared to the pure polymer.