Algal strain and methods for producing simple sugars
Inventors
Barney, Brett M. • Vogel, Evelyn • Mancipe, Natalia Calixto
Assignees
University of Minnesota System
Publication Number
US-12270063-B2
Publication Date
2025-04-08
Expiration Date
2042-07-21
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Abstract
Culturing S. glucoliberatum PABB004 under conditions effective for the S. glucoliberatum PABB004 to secrete simple sugars into culture medium. In one or more embodiments, the conditions include a pH of 6.0 to 8.5. In some cases, the culture can include a second organism. A co-culture includes S. glucoliberatum PABB004 and a second organism, wherein the co-culture has a pH of 6.0 or greater. In one or more embodiments, the second organism is selected to produce a product of interest such as, for example, ethanol.
Core Innovation
This invention describes a microalgal strain, Scenedesmus glucoliberatum PABB004, that secretes simple sugars, specifically glucose and maltose, into the extracellular culture medium. The invention includes both monocultures and co-cultures of S. glucoliberatum PABB004 with a second organism, where the simple sugars provided by the microalga support the growth or product synthesis of the second organism. A key aspect of the method is that S. glucoliberatum PABB004 can secrete sugars efficiently under pH conditions of 6.0 or greater, which are suitable for many industrial and biotechnological applications.
The problem addressed by this invention relates to the limitations of current sugar feedstocks for fermentation processes, which include high cultivation times, complex post-harvest processing, and the expensive extraction and saccharification steps needed to obtain fermentable sugars from land-based crops or algal biomass. Existing sugar-secreting microalgae typically release sugars only at lower, less industrially compatible pH levels, and are limited in the range and concentration of fermentable sugars produced. There is a need for readily recoverable simple sugars from microbial sources without extensive processing.
By utilizing S. glucoliberatum PABB004, which was isolated and characterized for its sugar secretion phenotype and unique genomic features, the invention enables continuous or batch production of glucose and maltose in culture media, with the option to directly extract these sugars or feed them to other microorganisms in co-culture systems. The invention details methods of culturing the microalga under defined pH ranges and using a carbon source, such as CO2, and includes methods to extract sugars or transfer cells for sustained production. The invention also defines co-cultures for the biosynthesis of products of interest (such as ethanol, triacylglycerides, wax esters, resorcinol, and bioplastics) by microbes that consume sugars secreted by S. glucoliberatum PABB004.
Claims Coverage
There is one independent claim defining the primary inventive feature of the invention.
Co-culture system with S. glucoliberatum PABB004 secreting simple sugars at pH 6.0 or greater
The invention provides a co-culture comprising: - A culture medium containing a carbon source; - S. glucoliberatum PABB004, which secretes at least one simple sugar into the culture medium in the presence of the carbon source; - A second organism, which is a microbe capable of feeding on the simple sugars secreted by S. glucoliberatum PABB004 into the culture medium; - Wherein the co-culture operates at a pH of 6.0 or greater. This system enables the production of simple sugars by S. glucoliberatum PABB004 in situ, allowing the second organism to utilize these sugars for growth or production of desired products.
The claim coverage centers on a co-culture system utilizing S. glucoliberatum PABB004 to secrete simple sugars for microbial use, with the distinctive requirement that the system operates at pH 6.0 or above.
Stated Advantages
Provides fermentable simple sugars (glucose and maltose) directly into culture media without the need for biomass pretreatment or saccharification steps.
Enables sugar secretion at higher, industrially relevant pH levels (6.0 and above), offering greater process flexibility and resilience than previously described sugar-secreting algae.
Broadens the pH range for extracellular sugar production, which facilitates co-culture with a variety of microorganisms for product biosynthesis.
Offers a potentially lower-cost and more rapid alternative to land crops as a sugar feedstock for fermentation-based production of fuels and commodity chemicals.
Documented Applications
Production of simple sugars (glucose and maltose) in culture media for recovery and downstream use.
Co-culture with a second microbe (bacterium, yeast, archaeon, or fungus) that utilizes the secreted sugars to synthesize products of interest, including ethanol, wax esters, triacylglycerides, resorcinol, and bioplastics (such as polyhydroxybutyrate).
Investigating nutrient exchange in biotechnological and industrial co-culture schemes using S. glucoliberatum PABB004 as a producer of fermentable carbon sources.
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