Impact of potential fermentation inhibitor present in sweet sorghum sugar solutions

Sweet sorghum is a sugar crop that can be integrated with other crops due to its relative short plant and harvest season.  The juice from the sweet sorghum stalk is generally less pure than juice from sugar cane and the juice also contains higher levels of inverse sugars than cane juice.  While less suitable for food quality sugar, sweet sorghum juice (and concentrated syrup) is very suitable for biofuel production.  However, it has been reported that aconitic acid, present in some sweet sorghum juices, is a potential inhibitor to ethanol-producing yeasts.  In this work, we determined the impact of aconitic acid on the respiration rate and ethanol titer by common brewer’s yeast.  Results from experiments with various acontic acid concentrations, inoculum sizes, and fermentation pH’s are presented.