Cellulose biosynthesis in nature and In Vitro: mechanisms and challenges

This review systematically compares the biosynthetic mechanisms of cellulose in plants and bacteria, focusing on the structure and function of their distinct enzymatic complexes. In bacteria, cellulose synthesis is driven by the BcsAB transmembrane complex alongside auxiliary proteins like BcsC and BcsD. In plants, rosette-shaped cellulose synthase complexes (CSCs), which are composed of multiple CesA catalytic subunits, synthesize cellulose microfibrils. This process is critically coordinated by auxiliary proteins, such as KOR1 and COBRA-LIKE proteins, which associate with or regulate the CSCs to ensure proper microfibril formation and crystallization. A central challenge in the field is the in vitro production of cellulose I, the native crystalline form with superior mechanical properties. While strategies such as enzyme extraction and heterologous expression in Escherichia coli enable cellulose production, they typically yield the less desirable cellulose II allomorph and face issues of low yield and instability. This review synthesizes current knowledge on key enzymes, in vitro synthesis methods, and resulting cellulose characteristics to identify key obstacles and future pathways toward the efficient bio-manufacturing of cellulose I for sustainable applications.