Characterization of exopolysaccharides from dextran- and fructan-forming microorganisms from sugar crops.
Approximately 8.1 million metric tons of sugar are produced in the U.S. each year with sugar beets and sugarcane contributions at 55% and 45%, respectively. While each of these crops are typically grown in different geographic locations with divergent climates, significant overlap exists in terms of post-harvest processing challenges. Microbes such as Leuconostoc that infect sugar beet roots not only result in potential crop loss, but also cause additional problems during post-harvest processing. For instance, microbial degradation of sucrose-rich processing streams results in sucrose losses and exopolysaccharide production that cause economic losses and operational problems during both sugar beet and sugarcane post-harvest processing. Here we isolated and characterized microbial isolates such as Leuconostoc sp. from sugarcane post-harvest processing streams that are also present in sugar beet post-harvest processing streams. We show that these strains produce exopolysaccharides in a sucrose-dependent manner. Exopolysaccharides were isolated from microbial culture supernatants and used for structural analysis including Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and other analytical chemistry techniques that may be useful for determining how composition, molecular weight, and structure may affect viscosity and susceptibility to dextranase treatment during processing. Ongoing work is also exploring qualitative and quantitative techniques to measure the presence of components beyond dextran, including levan fructans and non-sucrose sugars. We are very interested in extending sugarcane analyses to problems relevant for sugar beets, as there is significant overlap in post-harvest processing technologies for the two industries.