Evan Terrell, Gillian O Bruni and Isabel M Lima
USDA-ARS Southern Regional Research Center, New Orleans, LA 70124, United States of America; gillian.bruni@usda.gov
A persistent issue faced during raw sugar manufacturing is the presence of microbial contaminants such as bacteria (e.g., Leuconostoc spp.) and their associated exopolysaccharides (EPS). Many of these microorganisms consume sucrose directly, decreasing product value, while also generating EPS that may elevate viscosities and introduce operational challenges and associated costs. Bacterial isolates from processing facilities were collected and grown on high-sucrose liquid media in the presence of antimicrobial agents, a dextranase enzyme, and both treatments concurrently. We hypothesize that the presence of EPS confers some additional resistance to bacteria making them less susceptible to microbial control measures. Following growth experiments, bacterial growth and EPS production were quantified using optical density (OD) and culture viscosity measurements. Untreated controls of the Leuconostoc cultures had very high culture viscosity and OD, while those treated with antimicrobial agent were significantly lower in OD and viscosity. Application of dextranase as a treatment alone resulted in somewhat elevated OD and viscosity values for resulting culture solutions. The antimicrobial treatment was effective at inhibiting microbial growth; however, the lowest OD and viscosities in some instances resulted from concurrent application of both enzyme and biocide. These results provide evidence to support the hypothesis that EPS mitigation strategies may introduce improved microbial control when antimicrobial agents are applied. Through the application of enzymatic treatments, such as dextranase(s), bacteria present during sugarcane processing will have less opportunity to form EPS and biofilms. As a result, this could predispose dextran-forming bacteria to control measures, like the application of antimicrobial agents. Importantly, the application of EPS-mitigating enzymatic treatments with “biocides” could confer additional benefits for microbial control, beyond those realized through applications of these treatments individually. Overall, this strategy can improve operational efficiencies by decreasing required volumes/costs for processing aids and increasing raw sugar production.