Ensilage is a truncated solid-state fermentation in which organic acids accumulate to reduce pH and limit microbial activity. Ensilage technologies have long been used by ruminant livestock producers to preserve large quantities of cellulosic materials for feed. They are also currently used to both preserve and pretreat biomass feedstocks for further downstream conversion into biofuels and biochemicals. In this research, eight lactic acid bacteria (LAB) strains were evaluated for stabilizing sugar beet pulp so that this seasonally produced organic residue can be used for year-round biofuel production. Untreated (no LAB addition) samples were also evaluated. The most promising strains were selected based on growth kinetics, pH reduction, and lactic acid, acetic acid and iso-butyric/butyric acid accumulation. Treatment of sugar beet pulp with each of the LAB strains resulted in a pH drop from 5.7 to approximately 4.0 during ensiling. The greatest concentration of lactic acid, 0.882 mmol/dry-g, was observed in sugar beet pulp treated with Lactobacillus brevis.  This treatment had moderate accumulation of volatile fatty acids (0.537 mmol/dry-g).  Treatments containing L. fermentum also had a high final lactic acid concentration (0.851 mmol/dry-g) and relatively low volatile fatty acid accumulation (0.345 mmol/dry-g).  The results indicate treatment with either organism would stabilize sugar beet pulp during storage.
KEYWORDS: ensilage; lactic acid bacteria; sugar beet pulp; fermentation