Electronic System for Detecting Low-levels of Bacteria in Yeast Culture Inoculum

We aim to develop an electrical-sensor to detect low-levels of Lactic Acid Bacteria (LAB) in yeastinocula used to start large-scale ethanol cultures reducing the loss of productivity of the culture andthe incidence of "stuck" fermentations [Topic-Area 8.8: Biofuels and Bio-based products whereinwe will be "developing new and improved technologies that will lead to improvedcompetitiveness"]Currently contamination by LAB is detected indirectly: by measuring products (lactic-acid) in thefermentation-broth using HPLC or LC-MS. These methods have a high limit-of-detectioncorresponding to > 1 Million CFU/mL.The proposed sensing-approach relies on two phenomena. First: LAB can be killed rapidly usingantibiotics that have minimal effect on yeast-cells. Second: this death can be monitored in real-timeusing microchannel Electrical Impedance Spectroscopy (m-EIS). Briefly m-EIS relies on the factthat because living cells have a non-zero membrane-potential exposing them to a high-frequencyAC field results in charge accumulation at the cell-membranes (electrical-capacitance). Loss ofmembrane-potential accompanying cell death results in a drop in this capacitance. Hence if analiquot from a yeast inoculum is exposed to said antibiotics and monitored using m-EIS one shouldsee cell-death (drop in capacitance) only if LAB are present.In Phase I we will demonstrate the ability to detect LAB at concentrations as low as 100 -1000CFU/ml (3 orders-of-magnitude lower than incumbent methods). It is expected that screeninginocula using this technology will result in fewer incidences of "stuck fermentations" and alsoincrease the productivity of other cultures.