Sweet and sour potential of yeast from the Yarrowia clade

The food industry is witnessing a growing demand for food additives. Microbial fermentation is an attractive way to produce them using microorganisms, including the yeast Yarrowia lipolytica. Twelve species of the Yarrowia clade were screened for erythritol, mannitol and citric acid production from pure glycerol, glucose or fructose in four different media. During shake-flask cultures, only Y. lipolytica was able to secrete citric acid. Glycerol was found to be the best substrate for erythritol and mannitol biosynthesis by all the species. The six best candidate species for sweetener biosynthesis were cultivated in bioreactors. Up to 69.8 g dm⁻³ of total polyols with a yield of 0.59 g g⁻¹ was obtained for Candida oslonensis, the best sweetener producer. It secreted 44.6 g dm⁻³ of erythritol (Q_Ery = 1.16 g dm⁻³ h⁻¹ and Y_Ery/S = 0.4 g g⁻¹) and 34 g dm⁻³ of mannitol (0.29 g g⁻¹). Additionally, Candida hollandica and Yarrowia divulgata represent promising species for which media composition and culture parameters still have to be optimized.     

High selectivity of erythritol production from glycerol by Yarrowia lipolytica

The effect of different vitamins and nitrogen sources on the yield, productivity and selectivity of erythritol production from glycerol in batch and fed-batch cultures by Yarrowia lipolytica Wratislavia K1 strain was examined in the study.Thiamine was a vitamin necessary for efficient erythritol production and the yeast extract (YE) turned out to be its best source. The YE was additionally a very good source of nitrogen in this process. Erythritol production may be efficient in the media containing only yeast extract and crude glycerol. The application of a high substrate concentration (325 kg m⁻³) in the fed-batch system with pulsed addition of glycerol resulted in erythritol production of 201.2 kg m⁻³ after 168 h of cultivation. The mass fraction of by-products, such as other polyols and organic acids, did not exceed 10%. The study showed that by-products formation could be significantly reduced by the addition of a nitrogen source after glycerol depletion from the media. Wratislavia K1 strain does not utilize erythritol in the presence of other carbon sources and this feature was used in order to increase product selectivity up to 99.7% and protein content in yeast biomass up to 28.7%. The factors determining the use of biomass as animal feed, i.e. protein concentration and presence of metal ions, were discussed as well.     

Characterization and Analysis of Tetranitrate Esters

Thermal behaviors, vapor pressures, densities, and drop weight impact results, as well as analytical protocols, are reported for three tetranitrate esters: erythritol tetranitrate (ETN), 1,4‐dinitrato‐2,3‐dinitro‐2,3bis(nitratomethylene) butane (DNTN), and pentaerythritol tetranitrate (PETN). ETN and DNTN both melt below 100 °C and have ambient vapor pressures comparable to TNT. While LC/MS was shown to be a viable technique for analysis of all three tetranitrate esters, only ETN was successfully analyzed by GC/MS. Performance of these nitrate esters as evaluated in lab using the small‐scale explosivity device (SSED) suggested RDX≫DNTN>PETN>ETN. Detonation velocities were calculated using Cheetah 6.0. Since the starting material is now widely available, it is likely that law enforcement will find ETN in future improvised explosive devices. This paper with its analytical schemes should prove useful in identification of this homemade explosive.     

赤藓糖醇的发展及应用

本文着重介绍了目前世界赤藓糖醇市场的发展状况 ,并对其应用情况作了阐述。     

A comparison of heat transfer enhancement in a medium temperature thermal energy storage heat exchanger using fins

An experimental energy storage system has been designed using a horizontal concentric tube heat exchanger incorporating a medium temperature phase change material (PCM) Erythritol, with a melting point of 117.7 °C. Three experimental configurations, a control system with no heat transfer enhancement and systems augmented with circular and longitudinal fins have been studied. The results presented compare the system heat transfer characteristics using isotherm plots and temperature-time curves. The system with longitudinal fins gave the best performance with increased thermal response during charging and reduced subcooling in the melt during discharging. The experimentally measured data for the control, circular finned and longitudinal finned systems have been shown to vindicate the assumption of axissymmetry (direction parallel to the heat transfer fluid flow) using temperature gradients in the axial, radial and angular directions in the double pipe PCM system.     

Synthesis and Thermal Energy Storage Properties of Erythritol Tetrastearate and Erythritol Tetrapalmitate

Erythritol tetrapalmitate (ETP) and erythritol tetrastearate (ETS) were synthesized as novel solid‐liquid phase change materials (PCM) by means of the direct esterification reaction of the erythritol with palmitic and stearic acids. The ETP and ETS esters were characterized chemically using FT‐IR and ¹H NMR techniques. The energy storage properties of the esters were determined by DSC analysis. The results indicated that the ETP and ETS esters synthesized as novel solid‐liquid PCMs are promising materials for thermal energy storage applications at large scale such as solar energy storage, building heating or cooling, indoor temperature controlling, and production of smart textile and insulation clothing.     

Heat transfer enhancement in medium temperature thermal energy storage system using a multitube heat transfer array

An experimental energy storage system has been designed using an horizontal shell and tube heat exchanger incorporating a medium temperature phase change material (PCM) with a melting point of 117.7 °C. Two experimental configurations consisting of a control unit with one heat transfer tube and a multitube unit with four heat transfer tubes were studied. The thermal characteristics in the systems have been analysed using isothermal contour plots and temperature time curves. Temperature gradients along the three directions of the shell and tube systems; axial, radial and angular directions have been analysed and compared. The phase change in the multitube system was dominated by the effect of convective heat transfer compared to conductive heat transfer in the control system. The temperature gradient in the PCM during phase change was greatest in the radial direction for both the control and multitube systems. The temperature gradients recorded in the axial direction for the control and multitube systems during the change of phase were respectively 2.5 and 3.5% that of the radial direction, indicating essentially a two-dimensional heat transfer in the PCM. The onset of natural convection through the formation of multiple convective cells in the multitube system significantly altered the shape of the solid liquid interface fluid flow and indicates the requirement for an in-depth study of multitube arrangements.