Effect of a biocide treatment on microbes in sweet sorghum juice

Microbial contamination of sweet sorghum juice can result in loss of fermentable sugars used as bioproducts. A carbamate-based biocide in doses of 200 and 400 ppm used in the sugarcane industry was applied to sorghum juice collected from 4 and 8 in billets, or whole stalks, and growth of microbes was evaluated. Dosing with 200 ppm biocide reduced the microbial count in juice samples by approximately 99%, but a residual microbial count had potential to consume sugars in the juice and replicate. Increasing the dose to 400 ppm did not eliminate microbial contamination. Some of the contaminating microbes were found to be spore-formers, which enhances their ability to survive biocide treatment.   Key words: Bacteria, fungi, carbamate, billet.