Cultivation of Filamentous Green Algae for High Value Industrial Products

SummaryAlgae are heterogeneous groups of mostly photosynthetic organisms that are found in virtually every aquatic environment on earth. They exert influence on flux of carbon dioxide, generate large fraction of oxygen present in the earth's atmosphere and produce enormous quantity of organic carbon. Humans have long recognized the value of algae as a source of food and non-food products, and yet, despite the knowledge of its' benefits, humans have not developed method(s) for exploiting algae. A prime example of this failure is the recent experience with algal biofuel in which billions spent in public and private funding have not, to date, yielded a viable method for producing algal biofuel. Commercial algae business exists in production of high value algal extracts such as human dietary supplements, but this niche algae-based industry is a small segment of what could be a much larger industry. In this project, we propose to develop an innovative algae cultivation system that targets production of algal cellulose, a major component of algal cell that, unlike lipids and proteins, has not drawn much interest for commercial purposes. Lack of interest in algal cellulose is understandable since cellulose is the most abundant organic polymer on earth and is presently derived from woody and plant (cotton) biomass. Research, however, has shown that cellulose from some genera of algae (e.g., filamentous green algae) exhibit particularly high degree of crystallinity not seen in cellulose derived from woody or plant biomass. All algae produce cellulose that lack lignin, but some species like those from the filamentous green group exhibit preponderance of Iα cellulose as opposed to Iβ cellulose making them more thermodynamically reactive. Therefore, the combination of absence of lignin, presence of Iα cellulose as the preponderant cellulose, and higher degree of crystallinity make algal cellulose potentially more attractive than sourcing cellulose from woody and plant biomass. Lack of lignin and more thermodynamically reactive cellulose renders processing cellulose into derivatized cellulose products from algal biomass considerably easier (requiring less energy and chemicals) than processing cellulose from woody and plant biomass. Furthermore, the diversity of cellulose rich algal species offers the potential to produce processed cellulose such as dissolving pulp and microcrystalline cellulose that may have niche applications due to their size or shape.We aim to research the feasibility of cultivating a freshwater filamentous green alga Oedogonium. The chlorophycean green algal Oedogonium is cosmopolitan in freshwater habitats and has a cell wall composed largely of crystalline cellulose. A strain collected from Lake Mendota in Madison, Wisconsin by the project team exhibited cellulose content of 62% dry cell weight. Our experience with cultivating Oedogonium indicates that the particular species grew prolifically in hypereutrophic waters of ponds and in treated effluent of a secondary municipal sewage treatment plant. Energy input was minimal compared to other methods of cultivation and supplementation with carbon dioxide resulted in significantly higher growth rate. Research by others have shown that in an environment where mixed species of algae exist, Oedogonium often becomes the dominant species outcompeting other algae. The combination of prolific growth, large size, and ease with which Oedogonium can be harvested and dewatered make Oedogonium a viable target for large scale cultivation. Additionally, because Oedogonium produces exceptionally high crystalline cellulose, it holds the potential to be processed into high value derivatized cellulose products such as high purity dissolving pulp, microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC). Dissolving pulp market already exists and is projected to become larger with development of the middle class in countries like India and China. The m