Control of industrially relevant microbial isolates by antimicrobial agents: Implications for sugar factories

Microbial isolates from sugar crop processing facilities were tested for sensitivity to several industrial antimicrobial agents to determine optimal dosing. Hydritreat 2216 showed broad-spectrum activity against all bacterial isolates as well as Saccharomyces cerevisiae. Sodium hypochlorite showed broad-spectrum activity against all isolates, but at much higher effective concentrations. Hops BetaStab XL was effective against Gram-positive isolates. Magna Cide D minimum inhibitory concentration was lowest for S. cerevisiae and Zymomonas mobilis but was less effective against Gram-positive bacterial strains. Based on laboratory experiments, factory losses of sucrose from a single microbial species in the absence of antimicrobials could range from 0.13 to 0.52 kg of sucrose per tonne of cane. Additional improvements in sugar yield are anticipated from agents with broad-spectrum activity. A cost analysis was conducted considering sucrose savings due to antimicrobial application to provide estimates for break-even costs, which ranged from approximately $0.50 to $2.00/L for a given antimicrobial agent. Application of antimicrobial agents at minimal inhibitory doses for microbes results in optimal inhibition of microbial growth and sucrose consumption.