Laboratory Model of Anaerobic Manure and Food Waste Treatment for Energy Recovery
Eric Poomiwatracanont, Vidal Cortes, Erika Martinelli, Irene Chang
Mentors: Betty H. Olson, Jan Scherfig
The biological conversion of manure to simpler substrates and biogas can be monitored
by measuring gas production, as CO2 and methane, major metabolites, as Volatile Fatty
Acids (VFAs), and the dominant organisms in the reactor, Acidogenic and Methanogenic
bacteria. This project involved the development of a low-cost respirometer to measure the
real-time production of carbon dioxide and methane, a method to measure VFAs from
manure and pure culture samples, and the development of ribosomal DNA extraction
methods. The DNA extraction process was optimized considering the following factors:
blending times, dilution techniques, solids content, precision, accuracy, and purity. The
manure samples from the reactors were often high in solids, creating difficulty while
pipetting. To remedy this problem, samples were blended with water for a minimum of
two minutes to ensure even distribution and minimize the occurrence of blocking the
pipette tips. Sample dilutions showed that for every factor of ten the sample was diluted
the DNA yield would increase by a factor of ten but the precision would decrease.
Through many trials, the dilution for optimum yield and precision was a sample with a
total solid concentration of .01%. During DNA extraction it was noticed that with manure
samples the DNA purity was sometimes low, ranging from 1.1 to 1.3. Acceptable levels
of purity are 1.6 or higher. To increase purity of DNA, samples were incubated with
proteinase K, an enzyme that deactivates nucleases that often degrade DNA during
purification and remove contamination.