Erythritol, a four-carbon polyol, is a biological sweetener with applications in food and pharmaceutical industries. It is also used as a functional sugar substitute in special foods for people with diabetes and obesity because of its unique nutritional properties. Erythritol is produced by microbial methods using mostly osmophilic yeasts and has been produced commercially using mutant strains of Aureobasidium sp. and Pseudozyma tsukubaensis. Due to the high yield and productivity in the industrial scale of production, erythritol serves as an inexpensive starting material for the production of other sugars. This review focuses on the approaches for the efficient erythritol production, strategies used to enhance erythritol productivity in microbes, and the potential biotechnological applications of erythritol.

We consider the relationship between Hele-Shaw evolution with drift, the porous medium equation with drift, and a congested crowd motion model originally proposed by [MRS]- [MRSV]. We first use viscosity solutions to show that the porous medium equation solutions converge to the Hele-Shaw solution as m → ∞ provided the drift potential is strictly subharmonic. Next, using of the gradient flow structure of both the porous medium equation and the crowd motion model, we prove that the porous medium equation solutions also converge to the congested crowd motion as m → ∞. Combining these results lets us deduce that in the case where the initial data to the crowd motion model is given by a patch, or characteristic function, the solution evolves as a patch that is the unique solution to the Hele-Shaw problem. While proving our main results we also obtain a comparison principle for solutions to the minimizing movement scheme based on the Wasserstein metric, of independent interest. D. Alexander and I.

In this paper we investigate qualitative and asymptotic behavior of solutions for a class of diffusion-aggregation equations. Most results except the ones in section 3 and 6 concern radial solutions. The challenge in the analysis consists of the nonlocal aggregation term as well as the degeneracy of the diffusion term which generates compactly supported solutions. The key tools used in the paper are maximum-principle type arguments as well as estimates on mass concentration of solutions.

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This study isolated a novel erythritol-producing yeast strain, which is capable of growth at high osmolarity. Characteristics of the strain include asexual reproduction by multilateral budding, absence of extracellular starch-like compounds, and a negative Diazonium blue B color reaction. Phylogenetic analysis based on the 26S rDNA sequence and physiological analysis indicated that the strain belongs to the species Pseudozyma tsukubaensis and has been named P. tsukubaensis KN75. When P. tsukubaensis KN75 was cultured aerobically in a fed-batch culture with glucose as a carbon source, it produced 245 g/L of erythritol, corresponding to 2.86 g/L/h productivity and 61% yield, the highest erythritol yield ever reported by an erythritol-producing microorganism. Erythritol production was scaled up from a laboratory scale (7 L fermenter) to pilot (300 L) and plant (50,000 L) scales using the dissolved oxygen as a scale-up parameter. Erythritol production at the pilot and plant scales was similar to that at the laboratory scale, indicating that the production of erythritol by P. tsukubaensis KN75 holds commercial potential.