METABOLIC PROPERTIES AND KINETICS OF METHANOGENIC GRANULES

Two types of mesophilic methanogenic granules (R- and F-granules) were developed on different synthetic feeds containing acetate, propionate and butyrate as major carbon sources and their metabolic properties w ere characterized. The metabolic activities of granules on acetate, fo rmate and H2-CO2 were related to the feed composition used for their d evelopment. These granules performed a reversible reaction between H-2 production from formate and formate synthesis from H-2 plus bicarbona te. Both types of granules exhibited high activity on normal and branc hed volatile fatty acids with three to five carbons and low activity o n ethanol and glucose. The granules performed a reversible isomerizati on between isobutyrate and butyrate during butyrate or isobutyrate deg radation. Valerate and 2-methylbutyrate were produced and consumed dur ing propionate-butyrate degradation. The respective apparent K(m) (mm) for various substrates in disrupted R- and F-granules was: acetate, 0 .43 and 0.41; propionate, 0.056 and 0.038; butyrate. 0.15 and 0.19; is obutyrate, 0.12 and 0.19: valerate, 0.15 and 0.098. Both granules had an optimum temperature range from 40 to 50-degrees-C for H2-CO2 and fo rmate utilization and 40-degrees-C for acetate, propionate and butyrat e utilization and a similar optimum pH.