Comparison of sterilization techniques on different feedstock for sugar preservation and bioethanol fermentation

Although bioethanol production is already well-established in several countries, there are stages of the pro-duction process that could still be optimized. Feedstock storage is often one of the least efficient part of the bioethanol production process because no sugar preservation techniques are used, which more than often results in sugar waste to microbial contamination. In addition, the trend for future biorefineries is the use of diverse feedstocks, which implies as well that there might be different storage requirements involved. Hence, this study aimed to compare the preservation efficiency of three sterilization techniques on sugar beet molasses and juice including filtration, pasteurization, and ozonation. Results showed that for the molasses, filtration and pasteurization allowed conservation of 80% of the total fermentable sugars, while ozone treatments allowed maintaining 65% readily available for downstream fermentation. In the case of beet juice, pasteurization and ozonation allowed a higher conservation of total fermentable sugars (61% and 41%, respectively) than the filtration treatment for which only 29% was achieved. The sterilization techniques did not have a negative impact on the fermentation performance, with positive controls presenting similar efficiency to fermentation control (similar to 70%). It hence shows that the feedstock composition is a key element in the identification of the most suitable and if possible cost-effective preservation technique.