ALGAL GLYCEROL PRODUCTION: INITIAL GLYCEROL SYNTHESIS KINETICS

A review of previous work has allowed presentation of a unified conceptual model relating the important biochemical mechanisms involved in regulating glycerol production in halophilic algae. Experimental results on the initial rate of glycerol synthesis are reported which are used to indicate sodium transport may be the rate limiting step. These and other related results are discussed in relation to the model, and to algal glycerol process considerations.     

MACROSCOPIC KINETIC MODELS OF GLYCEROL BATCH FERMENTATION WITH OSMOTOLERANT YEAST

Kinetics of glycerol production by fermentation with osmotolerant yeast Candida krusei was studied. Suppositions of cell negative effect on and glucose inhibition in specific growth rate and glycerol assumption for energy maintenance were made. Based on the suppositions, a set of unstructured kinetic models including cell groWth, glucose consumption and glycerol accumulation rate was proposed. To avoid the significant decrease of produced glyccerol in the latter fermentation stage, the fermentation was suggested to be ended when the concentration ratio of glycerol to glucose is close to 7.     

玉米浆浓度对甘油发酵的影响及动力学

引　言甘油是重要的化工原料 ,在日常生活中有广泛的用途 ,其生产前景看好[1,2 ] .甘油的生产方法主要有 3种 :肥皂和脂肪酸工业的副产品、化学合成法和微生物发酵法 .发酵法利用的是可再生资源(木薯、玉米、糖蜜等 ) ,在药品和食品上使用的竞争优势明显 ,因此具有巨大的发展潜力 .但是要使发酵法生产甘油成为真正具有生命力的产业 ,必须在提高甘油收率、降低成本等方面开展工作 .由于发酵培养基中玉米浆 (ＣＳＬ)的含量决定了菌体浓度 ,从而影响发酵过程中用于生长和维持所消耗的葡萄糖 ,进而影响甘油的收率 ,所以研究玉米浆浓度对甘油发酵…     

以氯化钠为渗透压调节剂的甘油间歇和连续发酵

引　言耐高渗酵母发酵生产甘油是于 2 0世纪 5 0年代开始研究的[1] ,到目前为止取得了很大的进展 .但是对其研究主要集中在间歇工艺方面 ,而连续化法作为一种有效的操作方式一直是人们追求的目标 .早在 2 0世纪 60年代 ,Ｄａｗｓｏｎ[2 ] 就对Ｓａｃｃｈａｒｏｍｙｃｅｓｒｏｕ     

VISCOSITY OF GLYCEROL AND ITS AQUEOUS SOLUTIONS MEASURED BY A TANK-TUBE VISCOMETER

In this paper we demonstrate several series of experiments for the measurement of viscosity of neat glycerol and its aqueous solutions using a tank-tube viscometer. Measuring viscosity of highly viscous liquids with the tank-tube viscometer is easier than other types of viscometers. This inexpensive viscometer continuously generates numerous reproducible viscosity data of highly viscous neat glycerol and its aqueous solutions under given experimental conditions such as a desired temperature and a desired concentration of water in aqueous glycerol solutions.

Fabricating the tank-tube viscometer is inexpensive, since this viscometer does not need sophisticated accessories such as a high-pressure liquid pump, a sensitive pressure sensor, and an accurate flow meter. The tank-tube viscometer consists of a large-diameter reservoir and a long, small-diameter, vertical tube.

The viscosity equation was developed under the following assumptions. Both the quasi steady state approach and the negligible friction loss due to a sudden contraction between the reservoir tank and the tube are valid. The kinetic energy of the emerging stream from the bottom end of the vertical tube of the tank-tube viscometer also is assumed to be negligible. Very viscous glycerol and its aqueous solutions were used to test the viscometer by comparing viscosity values from the viscometer with those from literatures.

The main objective of this study is to demonstrate effects of water as well as temperature on viscosity of aqueous glycerol solutions, applying experimental data of accumulated amounts of aqueous glycerol solutions at various drain durations to the newly-developed viscosity equation for the fabricated tank-tube viscometer.     

Candida krusei 的分批培养与补料分批培养生产甘油

采用Candida krusei分批发酵生产甘油,因菌体生长形成副产物,甘油总得率仅为0.377g/g。生长阶段改用流加培养,限制葡萄糖的供应,然后补入剩余葡萄糖。这样,菌体对葡萄糖的得率系数和甘油总得率比分批培养分别提高了0.258g/g和0.058g/g,最终甘油浓度提高了10g/L 左右。     

周期变温和后期通氮气或二氧化碳发酵对提高甘油产量的影响

引　言甘油是一种重要的工业原料 ,广泛用于化工、食品、医药等领域 .生产甘油的方法主要有化学合成、油脂水解和肥皂液提取以及糖类原料经微生物作用的发酵法 .由于化学合成甘油的产量有限 ,肥皂行业受到洗涤剂行业的冲击 ,肥皂生产减少 ,甘油产量也随之下降 ,市场供不应求 .因此 ,发酵法以其原料来源丰富、设备简单等得到人们的青睐[1～ 3 ] .发酵法是以糖类为原料 ,利用某些微生物在一定条件下通过代谢作用而产生甘油 .用耐高渗酵母发酵生产甘油的研究已有许多文献进行了报道[4～ 7] ,我国在这方面也做了大量的研究工作 .但大规模工业化…     

OPTIMAL FEED STRATEGY FOR FED-BATCH GLYCEROL FERMENTATION DETERMINED BY MAXIMUM PRINCIPLE

Optimal glucose feed strategy for glycerol fed-batch fermentation was investigated by Pontryagins maximum principle to maximize the final glycerol yield. The problem was solved by a nonsingular control approach by selecting the culture volume as the control variable, then the general optimal feed profile was numerically determined.     

反复分批发酵法制备甘油过程中的影响因素

对游离耐高渗酵母细胞反复分批发酵生产甘油的影响因素进行研究 ,结果表明 :反复分批发酵过程中所需的最优玉米浆浓度低于普通的分批发醇 ;较好的菌体反复利用时机确定为发酵液中残糖降至约 1% ,即细胞活性为 60 %时 ;在菌体的反复利用过程中残留在菌体中的代谢产物的累积会对甘油发酵产生抑制作用 ,每次菌体利用之前用无菌水洗涤菌体一遍可消除抑制.     

甘油环缩甲醛丙烯酸酯的合成与应用

合成了甘油环缩甲醛丙烯酸酯,并用ＩＲ、Ｈ－ＮＭＲ检测其结构,它含有加聚必不可少的双键,可作为ＵＰＲ的活性稀释剂和交联剂,并赋予树脂空干性。     

甘油连续生物歧化过程的过渡行为及其数学模拟

用肺炎杆菌将甘油转化为１,３－丙二醇过程对稀释速率和底物进料浓度变化的过渡行为反映了细胞生长和胞内物质代谢在不同条件下存在着显著的差异。体系的过渡响应取决于操作条件变化前后系统所处的状态,当底物浓度由限制状态向剩余状态过渡时,甘油的残余浓度不断上升,而乙醇的浓度则逐渐下降,同时生物量、１,３－丙二醇和乙酸的浓度呈现先增后降的趋势。本文用“甘油浓度变化速率”的概念修正了菌体生长模型,并对甘油歧化过程     

EFFECTS OF GLYCEROL ON THE DRYING OF GELATIN AND SUGAR SOLUTIONS

ABSTRACT

The water diffusion coefficients D of gelatin, sucrose arid maltodextrin solutions were determined from the isothermal drying (desorption) rates as a function of water content u ( 0.1 < u < 1.0 ) and temperature (303, 323K) for various glycerol contents ( W_G = 0 – 0.43 kg-glycerol/kg-total solid). When W_G was above 0.2, D increased especially at low water contents (u < 0.25). The desorption isotherms were measured for the same systems. The equilibrium water content at a given water activity A_w decreased with an increase in W_G when A_w < 0.5. This indicates that adding glycerol weakens the water-solute interaction especially at low water contents. Glycerol also softened gelatin films and resulted in loss possibilities of surface cracks during drying.     

Thermodynamic and kinetic behavior of glycerol aerosol

Glycerol and propylene glycol mixtures are common carrier solutions in electronic cigarettes. Aerosols produced from these mixtures will evaporate quickly in a dry environment due to their high volatility. In a humid environment, such as the lungs, the kinetics of evaporation and hygroscopic growth determine the evolution of aerosol plume glycerol. Here, we apply a temperature and relative humidity-controlled hygroscopicity/volatility tandem differential mobility analyzer system to study the growth and evaporation kinetics of glycerol aerosol over a wide range of temperature, relative humidity, and residence times. Results show that at dry conditions glycerol aerosols evaporate within seconds at temperatures warmer than 20°C and that the accommodation coefficient of glycerol vapor on dry glycerol particles is 0.8. Under humidified conditions, the mutual depression of vapor pressures of the aqueous glycerol/water solution slows the glycerol evaporation rate consistent with thermodynamic and kinetic model predictions. Model calculations show that water vapor aided condensation of glycerol can occur at high relative humidity for glycerol vapor concentrations that result in glycerol particle evaporation under dry conditions. The combined results will help with constraining computational modules that model the evolution of glycerol-containing aerosols along a prescribed thermodynamic trajectory.

Copyright © 2016 American Association for Aerosol Research     

Supercritical water gasification of glycerol: Intermediates and kinetics

In this paper, the liquid products from supercritical water gasification (SCWG) of glycerol were analyzed and some intermediates were identified. A simplified reaction pathway for gases production from SCWG of glycerol was proposed. The first quantitative kinetics model for describing the gaseous products (H₂, CO, CH₄ and CO₂) of SCWG of glycerol was developed. The model comprises seven reactions to describe the typical reactions in SCWG, and the reaction rate constant of each reaction was obtained by using the nonlinear least-square fitting method. The reaction rate analysis showed that the main sources of hydrogen yield were glycerol pyrolysis and steam reforming of intermediates, while the hydrogen yield from water–gas shift reaction (WGSR) was very small. The temperature estimated by the kinetics model for completely SCWG of glycerol solution was given. In addition, the sensitivity analysis of rate constant of WGSR was done based on the model.     

Heterogeneous numerical modelling for the auto thermal reforming of crude glycerol in a fixed bed reactor

A mathematical model for the catalytic autothermal reforming (ATR) reaction of synthetic crude glycerol to hydrogen in a fixed bed tubular reactor (FBTR) and over an in-house developed metal oxide catalyst is presented in this work. The heterogeneous model equations account for a two-phase system of solid catalyst and bulk feed gas. Also, the ATR of crude glycerol reaction scheme and intrinsic kinetic rate model over an active, selective, and stable nickel-based catalyst were integrated in the developed model. Also, the model was validated using experimental data generated in our labs for the ATR of synthetic crude glycerol. The modelling results adequately described the detailed gas product composition and distribution, temperature profiles, and conversion propagation in the axial direction of the fixed bed reactor over a wide range of reaction temperature (773-923 K) and mass-time (12.71-158.23 g cat·min·(mol C)^-1). The crude glycerol conversion predicted with the model showing a close resemblance to those obtained experimentally with an average absolute deviation (AAD) of less than 8%. The maximum crude glycerol conversion and hydrogen yield were found to be 92% and 3 mol hydrogen/mol crude glycerol, respectively. Also, the gas product concentration profile in the reactor was adequately described (90%) accuracy with a hydrogen concentration of 39% (volume).     

Absorption of glycerol and its effects on the physical properties of a collagen material: Leather

An aqueous solution of glycerol was applied to a polymeric biomaterial, leather, to evaluate its effects on the physical properties of leather, particularly stiffness. The initial strain energy, Young's modulus, and acoustic‐emission methods were used to characterize the stiffness of the resultant leather treated with these glycerol solutions. The measurements revealed that the glycerol treatment significantly reduced the stiffness of the dried leather, indicating the strong lubrication function of glycerol for leather. Experiments were also conducted to investigate the mechanism of glycerol adsorption into the leather matrix. Fick's second law of diffusion was employed to systematically derive a mathematical model for the absorption rate. The effect of temperature on the absorption rate was also included in the model by incorporation of the Arrhenius equation into Fick's second law of diffusion. The resultant model fits the experimental data very well. It not only depicts the mechanism of absorption but also predicts the absorption rate as a function of key variables. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1221–1231, 2003     

醋酸甘油酯对酚醛树脂交联反应的催化作用

利用pH值的测定和凝胶转化率的计算,研究了醋酸甘油酯（三醋酸甘油酯、二醋酸甘油酯、一醋酸甘油酯）对甲阶酚醛树脂交联反应的催化作用,以及体系pH值对催化作用的影响。结果表明：在同样条件下催化速度：三醋酸甘油酯〉二醋酸甘油酯〉一醋酸甘油酯。体系的pH值对催化作用有重要的影响,pH值〉12．5时交联反应不能进行,pH值越低,交联反应的速度越快;pH值对一醋酸甘油酯的催化作用影响最大,二醋酸甘油酯次之,三醋酸甘油酯最小。增加醋酸甘油酯的浓度和升高反应温度使交联反应的速度加快。     

Glycerolysis of Soybean Oil with Crude Glycerol Containing Residual Alkaline Catalysts from Biodiesel Production

The glycerolysis reaction of soybean oil was evaluated using crude glycerol obtained from the transesterification of soybean oil with methanol, catalyzed by sodium methoxide and sodium hydroxide, without any purification step other than the methanol removal. Crude glycerol with the lower content of remaining inorganic catalyst produced the highest concentration of monoglycerides (about 42%). The effect of the addition of water on the glycerolysis reaction was analyzed, evidencing a low formation rate of products in the first stages of the reaction due to the transformation of the inorganic catalyst to soaps, which are weaker bases. The sample of crude glycerol that led to the best results was evaluated at several temperatures. It was observed that the reaction with crude glycerol exhibits a lower formation rate of monoglycerides at low temperatures (160 and 180 °C) compared with the reaction with pure glycerol and catalyzed with NaOH. This behavior was explained by the lower activity of the soaps present in the crude glycerol respect to the inorganic base. Above 200 °C the reaction is very fast and the monoglycerides formed are consumed to produce diglycerides.     

Nd -P -O催化剂上甘油脱水生产丙烯醛反应性能

分别以磷酸、焦磷酸和三聚磷酸为磷源制备了稀土磷氧类化合物,并以甘油脱水生产丙烯醛反应为模型反应,对该类化合物催化性能进行比较.研究反应温度、载气流速、反应空速和反应溶液浓度对催化剂性能的影响,得到最佳反应条件:反应温度320℃,载气流速30 mL · min-1,甘油空速227 h-1,甘油水溶液浓度36.5％,此条件...