Bioprocess design for the microbial production of natural phenolic compounds by Debaryomyces hansenii.

Debaryomyces hansenii NRRL Y-7426 metabolised ferulic acid into different phenolic compounds using a factorial design where glucose concentration (in the range of 1-20 g/L), peptone concentration (2-20 g/L) and yeast extract concentration (0.2-10 g/L) were the independent variables. The interrelationship between dependent and operational variables was well fitted (R (2) > 0.95) to models including linear, interaction and quadratic terms. Depending on the glucose and nitrogen concentrations, which redirected the metabolism, the major degradation products were 1,226.2 mg 4-vinyl guaiacol/L after 72 h (molar yield of 86.0 %), 1,077.8 mg vanillic acid/L after 360 h (molar yield of 91.1 %) or 1,682.6 mg acetovanillone/L after 408 h (molar yield of 98.8 %) in fermentations carried out with 2,000 mg ferulic acid/L. Other metabolites such as vanillin, vanillyl alcohol or 4-ethylguaiacol were present in lower amounts.

Development of culture media containing spent yeast cells of Debaryomyces hansenii and corn steep liquor for lactic acid production with Lactobacillus rhamnosus.

To develop a cost-effective fermentation medium, biomass of Debaryomyces hansenii coming from xylitol production and corn steep liquor was evaluated for lactic acid production by Lactobacillus rhamnosus in glucose-containing media. Glucose consumption and lactic acid generation were followed using a variety of media made with different nutrient supplementation. Under selected conditions, media containing glucose, biomass of D. hansenii and corn steep liquor as unique components led to product yields similar to those obtained in a fully supplemented medium.