Monday, July 25, 2011
Grand Ballroom, 5th fl (Sheraton New Orleans)
Zymomonas mobilis (Zm) is an industrially useful bacterium that can produce ethanol at rates and concentrations exceeding that of yeast. This has made Zm, an attractive alternative or supplement to Saccharomyces cerevisiae for ethanol production and there have been attempts to genetically modify the microbe for enhanced ethanol production. However its use may alter the nutritional content of distillers grains (DG) as an animal feed. Therefore in this study, a Polymerase Chain Reaction (PCR) based assay has been developed for the detection of Zm in DG. PCR is superior to culture based detection systems, since it can detect nonviable or non-culturable bacteria. Eight strains of Zm were obtained from the ARS culture collection in Peoria, IL. Overnight cultures were serially diluted, and inoculated into DG for testing into relevant matrices. Assay time was reduced through the use of whole bacterial cells instead of extracted DNA as a PCR template. Primer sequences specific for Zm targeted a 900 bp rRNA overlapping region of the 16S, and the 23S genes. The sensitivity of whole bacterial cells was comparable to extracted DNA. The limit of detection was 10^4 cfu/g or 5 cfu/PCR in 5 hours after addition of buffer supplemented with detergent and 10 cfu/g after 22 hours of overnight enrichment. This assay is rapid compared to traditional plate culture methods which take up to 72 hours. Field DG samples (n=25) were tested with the results indicating that Zm is not being currently used by the biofuel industry.
Keywords: distillers grains, Zymomonas, bioethanol