Isolation and analysis of microbial contaminants from Louisiana raw sugarcane factories

Authors: Bruni, Gillian; Qi, Yunci; Klasson, K Thomas; Lima, Isabel; Terrell, Evan

Submitted to: International Sugar Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2022
Publication Date: 9/5/2022
Citation: Bruni, G.O., Qi, Y., Klasson, K.T., Lima, I.M., Terrell, E. 2022. Isolation and analysis of microbial contaminants from Louisiana raw sugarcane factories. International Sugar Journal. 124(1485):530-538.

Interpretive Summary: An ongoing challenge to raw sugar production is reducing sucroses losses and problematic polysaccharides due to microorganisms that contaminate sugar factories and juices. To better understand the role of microbes present in raw sugar factories, we isolated and characterized multiple isolates from locations in Louisiana. In addition to some well-known microbes, we also identified additional bacteria and yeast that appear to play a role in sucrose losses. Some of these microbes produce dextrans while others produce fructans, both of which contribute to viscosity problems and potential penalties during raw sugar production. Bacterial isolates were tested for sensitivity to sodium hypochlorite (bleach). The results indicated that much higher concentrations of sodium hypochlorite are required to significantly inhibit growth of these organisms than is typically used in sugar factories. These isolated microorganisms will be used for further studies will be aimed at improved microbial and polysaccharide control measures.

Technical Abstract: A persistent challenge during raw sugar production is the mitigation of the growth of microbes that consume sucrose and produce polysaccharides. Here, we developed a sugarcane-based growth medium, CJ+, and utilized molecular microbiology approaches to isolate and identify microorganisms present in Louisiana raw sugarcane factories. In addition to well-known Leuconostoc, several other bacterial and yeast genera were identified. All these microbes contribute to sucrose degradation, with some consuming greater quantities as measured by HPLC. We also show that extracellular polysaccharide (EPS) production varies between isolates, and that EPS production by Leuconostoc and Gluconobacter isolates is sucrose-dependent, whereas Pantoea is not limited to sucrose for EPS production. Growth assays in sodium hypochlorite (bleach) indicates that 600-800 ppm is required for significant growth inhibition of these bacteria. These isolated microorganisms will also be used for further studies aimed at improving microbial and polysaccharide control measures that are crucial for increasing profits by decreasing sucrose losses and reducing costs.