This Small Business Innovation Research (SBIR) Phase I project, if successful, will demonstrate the application of filtered light to increase the productivity of large scale microalgal cultivation. Traditionally, algae growth has depended on natural solar radiation to be economically viable. However, natural sunlight is not optimized to promote growth and contains spectra (such as UV, or IR) that are detrimental to algal cells. Special lighting sources such as laser and LED to boost beneficial wavelengths to increase algal growth is possible but cost prohibitive. This project utilizes cost effective thin-film material to selectively transmit optimal light spectra from the sunlight to algal cultures. The plan is to apply multiple customized filters to algae cultivation and measure the impact on cell growth and morphology, chemical production, bioreactor performance. The goal of the project is to show decreased energy costs and increased system productivity.
The broader impact/commercial potential of this project will be improving productivity and economics of photosynthetic systems, such as algae and terrestrial horticulture. This project will lead to better understanding of the influence of targeted light on algae and could lead to novel processes for producing fuel and chemicals. Furthermore, increased efficiency of algae growth systems for producing commercially useful products, such as fuel and other chemicals, can lead to economic and environmental benefits. Increased light utilization efficiency introduces cost savings. These improvements lower barriers to entry in the algae sector, which could increase activity in this field. In addition to being beneficial for algal growth, the light filtering technology pioneered in this project could be applied to other plant growth industries, further fueling the worldwide boom in protective agriculture. These wide applications also will promote the advanced manufacturing of similar specialty materials for use in other fields.
It is well established that light intensity affects algae growth, but, in addition to intensity, the quality of the light source plays an important role in mass algal cultivation. Although commercially viable microalgae cultivation must rely on the sun to drive photosynthesis, natural sunlight is not optimized for algal cell growth due to its wide light spectra. For example, ultra-violet (UV) and infrared red (IR) radiation can impair cell metabolism, leading to decreased productivity. However, specific wavelengths of visible light are beneficial to microalgae cells. For example, Tipnis & Pratt and others found that light with strong blue wavelengths and reduced red wavelengths resulted in increased lipid content, while the opposite wavelength profile (high red wavelengths and low blue wavelengths) resulted in a high protein content. Therefore, the use of appropriate wavelengths of light in algal cultivation is an effective way to enhance algal cell growth and alter chemical composition. The goal for this project was to create a scalable, low-cost filter technology to increase the efficiency of photoautotrophic microalgae cultivation. Previous algae research has focused on the effects of light quality with the use of artificial light sources. With the support of the National Science Foundation SBIR award (IIP-1345966) and the Kentucky Cabinet for Economic Development (KSTC-184-512-14-192), WaveTech translated such research into creating a nano-material based filter to selectively transmit specific wavelengths of natural sunlight. The NSF SBIR Phase I feasibility study had three specific objectives: 1) design and manufacture thin-film based optical filters for algae; 2) implement these filters to affect the light quality for algae grown in a variety of photobioreactors; and 3) evaluate the impact of these filters on the growth of algae. WaveTech successfully designed and manufactured two filter designs with different transmission spectra. WaveTech then partnered with Iowa State University where the filters were applied to three different algae bioreactor systems: cultivation flasks, flat panel bioreactors, and rotating algal biofilm reactors. Once cultivation cycles ended, the cultures were analyzed for their chemical composition. Initial results indicated that the filters increased biomass production and shifted chemical composition of the algal cultures. WaveTech continued to expand on the Phase I feasibility study by partnering with the University of Kentucky Center for Applied Energy Research (UK CAER) for a Phase IB project. The UK CAER department has been working on their ongoing carbon sequestration project utilizing airlift photobioreactors. The UK CAER’s experience with airlift bioreactors and knowledge of their algae strain was combined with WaveTech’s efforts to test its filters on a UK photobioreactor system. The collaboration between WaveTech and UK CAER focused on three key target areas: 1) increasing carbon dioxide uptake by means of increasing biomass production; 2) decreasing heat-loads within reactors; and 3) increasing the longevity of acrylic tubular photobioreactors. At the end of the Phase IB period, WaveTech filters were found to have an impact on both biomass productivity and chemical composition. Both filters had a positive impact on the amount of cell protein content produced. To the best of our knowledge, this work shows the first ever use of filtered natural sunlight to improve the production of algae biomass. WaveTech has demonstrated the design and production of light filters to improve the quality of light for algae and has demonstrated that the application of these filters improves biomass production and impacts cell composition of C. vulgaris and S. acutus grown in multiple photobioreactor systems. Importantly, the filters designed and produced in this work are compatible with scalable manufacturing techniques. The application of the "red" and "blue" light filters produced in this study showed mixed impact on the growth rate and cell composition of C. vulgaris and S. acutus. Total lipid content per cell did not increase, but there was an effect on the fatty acids produced and carbohydrate production was increased in C. vulgaris. S. acutus and C. vulgaris showed increased cell protein content but an overall decrease in culture protein due to considerably decreased growth rate. Importantly, the impact of filters is dependent on bioreactor, likely due to geometry effects on lighting. The feasibility of using light filters to impact cell composition is established, but future work is needed to develop WaveTech filter designs tailored to specific species and bioreactor design based on commercial application.
