Optimization of erythritol production through fermentation using molasses as carbon source

Erythritol is a beneficial sugar alcohol that can be used as a sugar substitute for diabetic patients. Erythritol is a bioproduct produced by microorganisms as a response to high osmotic pressure and stress in the growth medium. High concentrations of carbon source substrate can increase the osmotic pressure and provide more nutrient supply for yeast growth and metabolism. Aside from that, an optimal carbon-to-nitrogen (C/N) ratio can also make the erythritol conversion pathway more favorable. Therefore, this research aims to determine the optimal concentrations of molasses as the carbon source, yeast extract as the nitrogen source, and the optimal carbon-to-nitrogen (C/N) ratio to achieve the highest erythritol productivity. The research also seeks to optimize NaCl concentrations and pH while comparing batch and fed-batch fermentation systems to determine which produces a higher erythritol yield. One-Factor-at-A-Time (OFAT) method was used to identify optimal production conditions. The study found that the highest erythritol concentration, 17.48 ± 0.86 g/L, was achieved using 200 g/L of molasses, 7 g/L of yeast extract (200/7), and 25 g/L of NaCl, with a yield mass of 0.262 ± 0.00 g/g and a volumetric productivity of 0.095 ± 0.021 g/Lh. The pH optimization revealed that the best erythritol production occurred within a pH of 5. Furthermore, fed-batch fermentation significantly increased erythritol concentration to 26.52 ± 1.61 g/L, with a yield mass of 0.501 ± 0.032 g/g and a volumetric productivity of 0.158 ± 0.01 g/Lh. These findings emphasize the importance of optimizing carbon source, nitrogen source and NaCl concentration, pH, and fermentation systems, particularly highlighting the benefits of fed-batch fermentation in maximizing erythritol production. These findings provide a solid foundation for improving erythritol yields for industrial applications.