Highly Dispersible and Crystalline Microalgal Nanocellulose Extracted Using a Low Environmental Impact Process

Nanocellulose is a bio-based, renewable, and biodegradable polymer that offers excellent mechanical properties, chemical stability, and a high density of hydroxyl groups, which support functionalization for tailored applications. Microalgae species with cellulosic cell walls provide a potentially rich source of nanocellulose and could avoid the need for energy intensive extraction or harsh chemical treatments (e.g., chlorine bleaching), required to purify nanocellulose from traditional biological sources (e.g., wood). The use of energetically costly shearing forces can be eliminated, as the fiber length is intrinsically limited by the dimensions of the microalgae cell. Here, we present a low environmental impact process (i.e., lower land, water, energy, and chemical requirements and green chemistry approaches) to produce high-quality nanocellulose from the microalga Glaucocystis nostochinearum. The purified nanocellulose fibers were ∼11 nm wide, with an average length of ∼2.7 to 3.7 μm long, were of an almost pure Iα allomorph, and were highly crystalline (crystallinity index = 87%; crystallite size 5.84 nm) and highly dispersible following rehydration. These properties make Glaucocystis nostochinearum nanocellulose a valuable resource for many applications, including valuable medical products and innovative materials that demand stiffness, stability, and barrier performance. Producing this nanocellulose as a product stream from multiproduct microalgae biorefineries could further reduce cost, environmental impact, and waste streams while increasing profitability. Mass scale up of microalgae production systems could also reduce costs and support access to specific bulk applications, including fabrication and building materials.