Environmental Implications of Nanocellulose: Biodegradation and Toxicity Potential

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

CBET 1236005 Studies over the past ten years have made it apparent that various commercially-relevant nanomaterials have harmful impacts on the environment. Unfortunately, there is a void of knowledge about the environmental implications of cellulose-based nanomaterials (nanocellulose). At the same time, the market for cellulose-based nanomaterials is expected to exceed a billion dollars by 2020. Given the estimated size of this market and the expected chemical and biological stability of nanocellulose there is a need to evaluate the environmental implications of these nanomaterials. Even though cellulose is generally considered to be an environmentally-friendly material given its omnipresence in woods, fibers, and tunicate animals, nanocellulose is both physically and chemically very different. These differences mean that it cannot be assumed that nanocellulose is as biodegradable and environmentally benign as cellulose in its native state. Thus, the proposed research will evaluate biodegradation (i.e., will nanocellulose naturally break down) and toxicity (i.e., is nanocellulose harmful to some organisms) utilizing bacterial communities relevant to wastewater treatment plants (WWTPs) and impacted water environments. WWTP microbes are especially relevant because as production of nanocellulose escalates, concentrations entering WWTPs will correspondingly increase. The study will focus on two hypotheses: Hypothesis One: Bacterial biodegradation of nanocellulose will be influenced by its surface properties (e.g., charge, hydrophobicity, and steric hindrance imparted by surface functional groups). Hypothesis Two: Negatively charged nanocellulose materials are non-toxic, while those possessing positively-charged surface modifications will be more toxic because they adhere to or disrupt cellular membranes (which are negatively charged). To test these hypotheses we have developed a research plan consisting of two integrated research tasks: Task 1. Evaluate the biodegradability of nanocellulose, and Task 2. Evaluate the toxicity and stress responses elicited by nanocellulose. Because very little is known about the environmental implications of nanocellulose production and use, the laboratory research efforts defined by Tasks 1 & 2 will be complemented by the parallel development of a life cycle assessment (LCA) inventory module for an undergraduate LCA course (ENGR 3134) at Virginia Tech. In this effort, undergraduate students taking ENGR 3134 will produce inventories that consider nanocellulose production and use. INTELLECTUAL MERIT: The proposed one year investigation is high risk/high reward and will establish critical baseline information on nanocellulose biodegradation and toxicity potential. Nanocellulose holds great promise as a potentially "green" nanomaterial. However, it is critical that this assumption be validated, especially as major production facilities are now going online. The physicochemical state (e.g., surface moieties, surface charge, aggregation state) of varying preparations of nanocellulose will be linked both to its biodegradability and microbial toxicity using complex microbial communities (anaerobic digester and wetland sediment) relevant to environments most likely to be impacted by disposal or other release. As the core material of nanocellulose is thought to be "inert", the approach could eventually provide a means to isolate the effects of surface chemistry and the behavior of nanomaterials as a whole in governing their environmental implications. This investigation will also advance the fundamental knowledge base of anaerobic cellulose degradation, a key biogeochemical process important for critical issues such as climate change and the development of alternative biofuels. BROADER IMPACTS: Two Ph.D. student researchers will be funded by this project and will gain interdisciplinary training across fields of nanotechnology, sustainable biomaterials, environmental microbiology, environmental engineering and application of molecular tools. The project will have institutional impact by catalyzing interdisciplinary collaboration between the VT Institute for Critical Technology and Applied Science (ICTAS) Sustainable Nanotechnology (SuN) and Water Sustainability research thrusts, which will provide complementary graduate student support. Interdisciplinary graduate education will also be enhanced via the companion VT SuN Interdisciplinary Graduate Education Program (IGEP), which will also provide opportunities for student support. The proposed LCA inventory will serve as an integral component of the undergraduate Virginia Tech Green Engineering program, providing a hands-on opportunity for in-class and independent undergraduate researchers, while also establishing a paradigm by which the "green" nature of nanotechnologies can objectively be assessed. Outreach efforts to women and economically underrepresented groups will be made to support community education as well as to aid in recruiting Ph.D. and undergraduate researchers to assist in this project.