Controlling bacterial contaminants in sugarcane ethanol fermentations

Fermentation;Sugarcane

Daum, Mary Angela ; Miller ; Michael J.

关键词: Fermentation;    Sugarcane;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/95527/DAUM-THESIS-2016.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Bioethanol from sugarcane has a lower carbon footprint than petroleum based fuels but the industry is plagued by various economic pressures, including product loss due to contamination of fermentation facilities. Lactobacillus species and other lactic acid producing bacteria from the feedstock and environment are important bacterial contaminants. Further studies focused on process optimization and validated the use of antibiotics and acid treatment to reduce ethanol losses due to bacterial contamination. Monensin, penicillin and virginiamycin have been shown to reduce bacterial counts in bioethanol but increased incidence of antibiotic resistant bacteria means alternative approaches are needed. To test efficacy of the antimicrobials hen egg white lysozyme, nisin and the combination of nisin and penicillin against representative contaminants a model system was developed. To mimic the typical Brazilian conditions, the model incorporates high initial yeast inoculum, fermentation times of twelve hours or less and final ethanol concentration of 5.5 to 6 % weight/volume. The impact of penicillin and nisin on bacteria isolated from sugarcane juice or adapted by successive passes in sugarcane juice in fermentation of sugarcane juice by Saccharomyces cerevisiae JAY291 was measured by counting the bacteria and yeast. In addition, ethanol and lactic acid titers were measured and by HPLC analysis of the fermentate. Plate counts revealed that the combination of 250 ppm of nisin and 2 ppm penicillin was the most effective treatment against Lactobacillus plantarum, as well as against a mix of L. plantarum and four other bacterial species. Combining nisin with penicillin could decrease the amount of penicillin used to control contamination and mitigate the risk of antibiotic resistant bacteria proliferating. This model system can be employed for testing other novel antibacterial measures such as bacteriophages, or engineered phage endolysins and bacteriocins.