Enhanced production of pullulan by two strains of A. pullulans with different concentrations of soybean oil in sucrose solution in batch fermentations

摘要

Aureobasidium pullulans is a microorganism that produces pullulan (homopolysaccharide) extracellularly through a fermentation process with sugars (maltose, d-xylose, sucrose and starch) as its carbon source. Pullulan is a linear polysaccharide of D-glycopyranose containing (1 ->4)-alpha and (1 -> 6)-alpha linkages at a 2:1 ratio, is highly soluble in water and has various applications in the food, packaging, film and pharmaceutical industries. Lipids, primarily oils, having antifoaming properties as well as nutritional particularities, are considered an essential additional carbon source for the growth of microorganisms, especially fungi. These nutrient sources are very important for the maintenance of microorganism cells. In fact, these positive effects are only achieved when the right source is added at both the right time and the right dosage into the broth of the fermentation process. In this research on pullulan production with the strains NRRL Y-6220 and NRRL Y-2311-1, it was found that the latter strain achieved better results for undesirable pigment formation, pullulan titer, time of maximum production (96 hours) and biomass yields than strain NRRL Y-6220, which also showed suitable results for biomass yields and cell morphology. However, the dark pigmentation of the strain NRRL Y-6220, formed through the process, makes its application unacceptable for foods and pharmaceuticals. Strain NRRL Y-2311-1 was shown to be a promising potential industrial microorganism, whose applications should be studied more in depth.