Identification of Soil Bacteria Capable of Utilizing a Corn Ethanol Fermentation Byproduct

A commercial corn ethanol production byproduct (syrup) was used as a bacterial growth medium with the aim to repurpose the resulting microbial biomass as a protein supplement in aquaculture feeds. Anaerobic batch reactors were used to enrich for soil bacteria metabolizing the syrup as the sole nutrient source over an eight-day period. Amplification of the V4 variable region of the 16S rRNA gene was performed using barcoded primers to track the succession of microbes enriched for during growth on the syrup. The resulting PCR products were sequenced using Illumina MiSeq protocols, analyzed via the program QIIME, and the alpha-diversity was calculated. Seven bacterial families were the most prevalent after the enrichment: Clostridiaceae, Alicyclobacillaceae, Ruminococcaceae, Burkholderiaceae, Bacillaceae, Veillonellaceae, and Enterobacteriaceae. Reactor isolates were identified at a species level using the full 16S rRNA gene and other biomarkers. These and other laboratory stock strains of interest were grown in microtiter plates with the syrup substrate to monitor growth rate and yield. Bacillus species, commonly used as probiotics in aquaculture, showed the highest growth rate and biomass yield of all monocultures examined. Binary combinations yielded no significant synergism between organisms, suggesting competition for nutrients instead of cooperative metabolite conversion.