Statistical media optimization for the biomass production of postharvest biocontrol yeast rhodosporidium paludigenum

A cane molasses-based medium for the biomass production of biocontrol agent Rhodosporidium paludigenum was statistically optimized. Molasses concentration (after pretreatment), yeast extract, and initial pH were identified by the Plackett-Burman design to show significant influence on the biomass production. The three factors were further optimized by central composite design and response-surface methodology. The statistical analysis indicated the optimum values of the variables were 89.98g/L for cane molasses, 2.35g/L for yeast extract and an initial pH of 8.48. The biomass yield at the optimal culture achieved 15.89g/L in flask fermentation, which was 2.1 times higher than that at the initial NYDB medium. In a 10-L fermenter, 18.97g/L of biomass was obtained after 36hr of cultivation. Moreover, the biocontrol efficacy of the yeast was investigated after culture optimization. The results showed the yeast harvested in the optimal medium maintained its initial biocontrol properties by reducing the percen age of decayed apples to below 20%.