Continental-scale insights into the sugarbeet diffusion juice microbiomes

Authors: BILL, MALICK - North Dakota State University; Eide, John; Fugate, Karen; Bolton, Melvin; KANDEL, HARI - Lake Superior State University; Kandel, Shyam

Submitted to: Microbiology Spectrum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2024
Publication Date: 9/23/2024
Citation: Kandel, S.L., Bill, M., Eide, J.D., Fugate, K.K., Bolton, M.D. 2024. Continental-scale insights into the sugarbeet diffusion juice microbiomes. Microbiology Spectrum. 12(11). https://doi.org/10.1128/spectrum.01093-24.
DOI: https://doi.org/10.1128/spectrum.01093-24

Interpretive Summary: Sugarbeet processing is the industrial process to produce sugar from sugarbeet roots. Bacterial contaminants in sugarbeet factory processing can consume sucrose leading to significant sugar loss, in addition to filtration problems during the juice purification. However, no studies have yet analyzed the bacterial contaminants in the raw sugar extracts in the U.S. and Canada. Therefore, the major objective of our study was to analyze the diversity of bacteria present in sugarbeet juice from roots harvested from different North American production regions that were stored for variable durations prior to processing. Sugarbeet juice samples were collected from nearly all sugarbeet processing factories across the U.S. and Canada. Sugarbeet juice samples were collected from two consecutive processing campaigns: 2021 and 2022 with four sampling times from late November to April. Results of the study revealed that lactic acid bacteria such as Leuconostoc and Lactobacillus are the major bacterial contaminants in raw sugarbeet juice. Additional studies indicated that, high raffinose concentrations in raw juice strongly favor the growth of Leuconostoc mesenteroides. The data gathered will be useful in benchmarking problematic bacterial populations during sugar processing. Ultimately, this will help the industry in developing targeted mitigation strategies to address the issue of bacterial contamination in factory processing, thus, reducing sucrose loss and minimizing the negative economic consequences thereof.

Technical Abstract: Bacterial contamination of raw diffusion juice poses unique challenges during the sugar extraction process. This study profiled bacterial communities by using full-length 16S rRNA amplicon sequencing and quantified the carbohydrate concentrations in raw diffusion juice samples received from sugar factory regions across the United States and Canada. Juice samples were collected at four time points during the 2021 and 2022 processing campaigns. Firmicutes was the dominant phylum from the raw diffusion juice samples collected during both campaigns and comprised 85.5% of total bacterial abundance. Lactic acid bacteria such as Leuconostoc and Lactobacillus were among the core genera which also dominated the bacterial community in raw diffusion juice. Positive correlations in the abundance of functionally and taxonomically related bacterial communities were identified. During the 2021 campaign, 44 bacterial genera were differentially abundant in raw diffusion juice extracted from sugarbeet roots in Periods 1 to 4. This number declined 6-fold during the 2022 campaign to three genera. The concentration of raffinose in raw diffusion juice positively correlated to the relative abundance of Leuconostoc. Furthermore, an in vitro assay was performed to assess the growth dynamics of Leuconostoc mesenteroides in sucrose or raffinose rich medium and observed the rapid consumption of both carbohydrates by this bacterium. This finding is important for deciphering microbial growth dynamics in raw diffusion juice that can be useful in minimizing sugar loss during the factory processing.