| If H2 yield rates from dark fermentation are to improve, methods must be designed that prevent interspecies H2 transfer to methanogens. Long chain fatty acids (LCFAs) have been proven to an inexpensive, natural methanogenic inhibitors. BES (2-bromoethanesulfonate), a synthetic chemical inhibitor, is also an effective methanogenic inhibitor. A BES concentration of approximately 50 mM was needed to reduce methane production to the level observed with 2000 mg/l LA. Maximum yields of 3.22 and 3.24 mol H2/mol glucose were observed in cultures containing 3000 mg/l LA and 100 mM BES at an initial pH 5.5, respectively. Cultures fed with LAU produced more H 2 than cultures containing LA during the first glucose injection period. The breaking of inhibitor additions into two equal increments separated by 24 hours did not improve H2 yields. However, methane reduction of 46% and 42% was observed for LA and BES, respectively. |
