Environmental Implications of Nanocellulose: Biodegradation and Toxicity Potential

过去十年的CBET 1236005研究表明，各种与商业相关的纳米材料对环境有有害影响。不幸的是，关于以纤维素为基础的纳米材料(纳米纤维素)对环境的影响的知识是空白的。与此同时，基于纤维素的纳米材料的市场预计到2020年将超过10亿美元。鉴于这一市场的估计规模以及纳米纤维素预期的化学和生物稳定性，有必要评估这些纳米材料对环境的影响。尽管纤维素普遍被认为是一种环保材料，因为它在木材、纤维和被囊动物中无处不在，但纳米纤维素在物理和化学上都有很大的不同。这些差异意味着，不能假设纳米纤维素与天然状态的纤维素一样可生物降解和对环境无害。因此，拟议的研究将利用与污水处理厂(WWTP)和受影响的水环境相关的细菌群落来评估生物降解(即，纳米纤维素是否会自然分解)和毒性(即，纳米纤维素是否对某些生物有害)。污水处理厂的微生物尤其相关，因为随着纳米纤维素产量的增加，进入污水处理厂的浓度将相应增加。这项研究将集中于两个假设：假设一：细菌对纳米纤维素的生物降解将受到其表面性质(例如，表面官能团赋予的电荷、疏水性和空间位阻)的影响。假设二：带负电荷的纳米纤维素材料是无毒的，而那些具有带正电荷的表面修饰的材料毒性更大，因为它们附着或破坏(带负电荷的)细胞膜。为了验证这些假设，我们制定了一个由两个综合研究任务组成的研究计划：任务1.评估纳米纤维素的生物降解性，以及任务2.评估纳米纤维素引发的毒性和应激反应。由于对纳米纤维素的生产和使用对环境的影响知之甚少，任务1和任务2定义的实验室研究工作将得到弗吉尼亚理工大学本科生生命周期评估(LCA)课程(ENGR 3134)的并行开发。在这项工作中，参加ENGR 3134课程的本科生将制作考虑纳米纤维素生产和使用的清单。智力优势：拟议的一年研究是高风险/高回报的，将建立关于纳米纤维素生物降解和毒性潜力的关键基线信息。纳米纤维素作为一种潜在的“绿色”纳米材料前景看好。然而，这一假设得到证实是至关重要的，特别是在主要生产设施现在正在上线的情况下。不同的纳米纤维素制剂的物理化学状态(例如，表面部分、表面电荷、聚集状态)将与其生物降解性和微生物毒性联系在一起，使用与最可能受到处置或其他排放影响的环境相关的复杂微生物群落(厌氧消化池和湿地沉积物)。由于纳米纤维素的核心材料被认为是“惰性的”，这种方法最终可能提供一种手段，在控制纳米材料的环境影响时，将表面化学的影响和纳米材料的整体行为隔离开来。这项研究还将推进厌氧纤维素降解的基本知识，这是一个关键的生物地球化学过程，对气候变化和替代生物燃料的开发等关键问题非常重要。更广泛的影响：两名博士生研究人员将由该项目资助，他们将获得纳米技术、可持续生物材料、环境微生物学、环境工程和分子工具应用等领域的跨学科培训。该项目将通过促进弗吉尼亚大学关键技术和应用科学研究所(ICTAS)可持续纳米技术(SUN)和水可持续研究推力之间的跨学科合作产生机构影响，这将提供补充的研究生支持。跨学科研究生教育也将通过配套的VT SUN跨学科研究生教育计划(IGEP)得到加强，该计划也将为学生提供支持机会。拟议的LCA清单将作为弗吉尼亚理工大学本科生绿色工程计划的一个组成部分，为课堂上和独立的本科生研究人员提供实践机会，同时也建立了一个可以客观评估纳米技术的“绿色”性质的范例。将向妇女和经济代表性不足的群体进行外联努力，以支持社区教育，并协助招募博士和本科生研究人员协助这一项目。

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.