Regional Competitive Grants
Project Title: Development of a microbial factory for efficient conversion of biodiesel glycerol to value-added products
Principal Investigators and affiliations:
Start Date: 11/1/2007 End Date: 10/31/2009
Project Abstract:
Biodiesel is a viable alternative fuel produced from domestic renewable resources. Utilization of biodiesel reduces air pollution, global warming, and the US dependence on foreign oil. Glycerol is a major byproduct from biodiesel manufacturing. As the biodiesel consumption expands rapidly, there is an urgent need for innovative conversion of glycerol to value-added products. We propose to convert biodiesel glycerol to potentially high-volume, high-value biosurfactants (rhamnolipids) by microbial fermentation. Biosurfactants have the potential to replace their synthetic counterparts in various applications because of their biocompatibility, environment-friendliness and extraordinary effectiveness. Well recognized for applications in agricultural (as biopesticides), chemical, environmental and medical industries, rhamnolipids are currently expensive to produce because of the low microbial productivity and the difficulty to meet the cells’ respiration need by aerating the highly foaming broth. We will address these challenges using an integrated multidisciplinary approach: (1) isolate the most productive strain(s) from biodiesel production sites; (2) metabolically engineer the strain(s) to channel intermediates more efficiently into rhamnolipids for maximal productivity; and (3) develop an advanced fermentation technology that uses biodiesel glycerol as substrate and supplements nitrate for cell respiration; thus, minimizing the foaming associated with excessive aeration. The advanced fermentation technology developed will serve as a platform for large-scale production of rhamnolipids and other value-added products. The success of the project will ensure economic benefit to the soybean farmers, will have significant economic, environmental and scientific impacts, and will enhance the feasibility of the long-term self-sustenance of both the biodiesel and biosurfactant industries.
We propose to develop the bacterium Pseudomonas aeruginosa into a biological factory for production of value-added compounds from biodiesel glycerol via microbial fermentation. We will first select the P. aeruginosa strain that is most tolerant to high concentrations of glycerol and produces the biosurfactant, rhamnolipids. Our collaborator, Dr. Kuo, has isolated 31 P. aeruginosa strains that are highly tolerant to 10% glycerol from a biodiesel plant. These strains will be analyzed for rhamnolipid production while growing on biodiesel glycerol. The selected strain(s) will be further improved via molecular genetic and metabolic engineering to enhance rhamnolipid production. The metabolic engineering will maximize the channeling of precursors into rhamnolipid production by deleting genes in competing pathways. In addition, an artificial bacterial operon containing the rhamnolipid biosynthetic genes will be constructed and placed under the control of a regulatable promoter on a multicopy plasmid to maximize the biosurfactant production. The engineered P. aeruginosa strain will be then utilized in an advanced microaerobic denitrification fermentation technology to achieve maximum rhamnolipid production. The Co-PD (Dr. Ju) developed this novel patent-pending fermentation technology that minimizes foaming due to aeration but maintains a relatively high cellular activity necessary for production of desired products. This microaerobic denitrification technology utilizes the online monitoring of NAD(P)H fluorescence which reflects cellular activity to carefully control oxygen or nitrate respiration of P. aeruginosa. P. aeruginosa is an ideal organism to be developed into a biological factory because it is easy to grow on a variety of compounds as nutrients including glycerol and because it is genetically amenable to produce several valuable compounds with potential industrial applications including the biosurfactants (rhamnolipids) and biodegradable plastic.
There are over 1 billion pounds of surplus soybean oil in U.S. annually. A wider use of biodiesel converted from the surplus soybean oil will bring significant economic benefits to the farmers and agricultural industries in addition to its environmental benefits as a renewable energy source and decrease emissions of greenhouse gases. Biodiesel production and sales in the U.S. have increased almost exponentially in the past few years, from <1 million gallons in 1999 to 25 million gallons in 2004 to 75 million gallons in 2005. It is expected to further increase to 1 billion gallons by 2010 or 2012.
A major barrier to increased biodiesel utilization is its higher cost. The conversion of biodiesel byproduct, glycerol, to value-added products is therefore very important for the commercial viability of biodiesel. Rhamnolipids are high-value biosurfactants that are used in bioremediation, textile industry, medical application, and as flushing agents and biological control agents in agriculture. Thus, the proposed research has significant overall benefits in rural economic development, energy efficiency/displacement, and local as well as global environments. Thus, the proposed research has significant overall benefits in rural economic development, energy efficiency/displacement, and local as well as global environments, in accordance with the Sun Grant Mission.
The outcomes of this research will include: (1) Development of genetic engineering and metabolic engineering tools that enable Pseudomonas aeruginosa to function as microbial factory for converting biodiesel glycerol to value-added products, (2) Successful development of advanced fermentation technology that utilizes the unique and versatile metabolic capabilities of Pseudomonas aeruginosa and serves as a platform for large-scale production of rhamnolipids and other value-added products, and (3) Development of an effective process that converts biodiesel glycerol to high value products so as to improve long-term sustainability of biodiesel industry and to generate new income for farmers and agricultural industries.
Reports and Publications:
Quarter 1 - 2008
Quarter 2 - 2008
Quarters 3-4 - 2008
Quarter 1 - 2009
Quarter 2 - 2009
