Evaluation of UF and RO in a cellulose saccharification process

The applications of membrane separation within the bioconversion of lignocellulosic materials to ethanol are studied, and this paper reports on cellulolytic enzyme recovery, and reduction of the product inhibition. The conversion of cellulose and hemicellulose to hexoses and pentoses is carried out in a laboratory scale UF-membrane reactor, and the sugars, which have an inhibiting effect on the enzymes, are continuously removed with the permeate. By optimizing the space velocity, the enzyme inhibition is minimized and the rate of hydrolysis is significantly increased.The recovery of the enzymes has also been investigated with regard to their mechanical stability and adsorption on the substrate. Prior to enzymatic hydrolysis, the raw material is subjected to a pretreatment to make the cellulose more accessible to the enzymes, and the effect of the pretreatment can easily be evaluated in the UF-membrane reactor.As a result of the continuous removal of products formed in the hydrolysis, the permeate has a low content of fermentable sugars, and to give the optimal conditions for the fermentation a concentration step is needed. Different RO-membranes are tested in a laboratory scale batch cell to be able to choose a membrane material, fit for filtration in larger modules.     

酶解反应与膜分离耦合连续制备酪蛋白磷酸肽

采用酶解反应与膜分离耦合新工艺连续水解全酪蛋白制备酪蛋白磷酸肽(CPPs)。考察了超滤膜对胰蛋白酶及底物溶液的截留效果;研究了初始底物质量浓度、初始酶质量浓度、反应体积、膜渗透通量等参数对反应器性能和反应转化率的影响规律;利用高效凝胶排阻色谱系统(HPSEC)对酶解产物进行检测分析;建立了酶膜反应器连续水解动力学模型,并对间歇与连续酶解过程进行比较分析,证明反应-分离耦合技术可使酶解效率及蛋白酶利用率大幅提高,并使产物得到调控与富集,为CPPs的酶法制备提供了一种更为有效的方法。     

Kinetic studies of wheat straw hydrolysis using sulphuric acid

The kinetics of cellulose and hemicellulose hydrolysis of wheat straw was studied using both isothermal and non-isothermal techniques in a batch reactor. Reactions were carried out between 100 and 210°C and product sugars were analyzed using a Bio-Rad HPX-87P liquid chromatographic column. A simple first order series reaction model was used for both cellulose and hemicellulose hydrolysis reactions and kinetic parameters were obtained for the Arrhenius rate equations for three different sulphuric acid concentrations (0.5, 1.O and 1.5%). Activation energies remained constant with acid concentration but the pre-exponential factors showed an increase with acid concentration. To minimize the amount of experimental data required and to achieve a unique solution to the kinetic parameters, the technique of combining isothermal and non-isothermal reaction data was studied.     

利用乳液酶膜反应器拆分萘普生甲酯实验研究

利用乳液酶膜反应器进行外消旋萘普生甲酯的水解反应,以制备光学纯对映体(S)-萘普生,反应同时从膜透过侧收集产物,实现反应分离一体化。实验研究了固定酶前后膜传质阻力和反应过程的水相跨膜通量,考察了透过侧的产物浓度、反应器的转化率、产量和对映体选择性。结果表明:固定化酶引起的传质阻力远大于膜本身的阻力;透过侧的产物浓度与水相渗透通量密切相关,通量较低时,产物浓度较高;固定化酶的初始反应速率为3.660μmol/(h.g),为自由酶的20倍以上,固定化酶的对映体过剩值为99%—100%,远高于自由酶的选择性,表明该反应体系为脂肪酶催化拆分反应提供了良好环境。     

基于蛋白质结构知识解析活性多肽的酶解制备反应行为(Ⅱ)酶解反应过程的集总动力学模型

以酪蛋白-胰蛋白酶反应体系为研究对象,建立了非均相酶解反应四集总动力学模型.研究中根据高效液相色谱分析结果及目标多肽所在区间,按分子量大小将酶解产物分段集总;依据反应机理与基本假设,构建集总反应网络;用包含酶失活、底物抑制和产物抑制常数的本征动力学方程描述各集总组分的反应行为,得到微分方程组形式的动力学模型;采用膜截分方法制得各集总组分,经实验测定和Marquardt法估算得到各集总组分动力学常数与反应网络各动力学参数;模型拟合与验证结果表明：所建多参数集总动力学机理模型具有良好的拟合性与外推性.     

高底物浓度纤维乙醇同步糖化发酵工艺的比较

引言日益加剧的能源危机和环境污染,正迫使人们寻求新的可再生替代能源。纤维乙醇作为一种重要的生物质替代能源,经过近40多年的发展,已经具备了实现工业化生产的潜力。为了进一步降低纤     

纤维素超临界水水解糖化研究进展

纤维素在超临界水中转化为简单糖是一种环境友好型的新技术。本文综述了纤维素在超临界水中水解糖化的反应机理、反应动力学和反应设备，以及反应产物和不同反应条件对产物组成的影响。并展望了今后该技术的发展前景。     

反应器操作方式对酶动力学拆分立体选择性的影响

描述了在批式反应器和连续流搅拌反应器（ＣＳＴＲ）中酶动力学拆分对映异构体的不同之处，从宏观反应器平衡角度，推导出了在ＣＳＴＲ反应器中不同于在批式反应器中的一定酶立体选择性（Ｅ）下，底物或产物的对映体过量值与反应的转化率之间关系的定量关系式。并通过商品脂肪酶及芽胞杆菌Ｅ－５３脂肪酶催化的萘普生甲酯的不对称水解反应得到了证实。分别在批式反应器和ＣＳＴＲ反应器中进行萘普生的酶法拆分，在一定转化率下，批式     

Reactor modeling and recipe optimization of polyether polyol processes: Polypropylene glycol

The reactor modeling and recipe optimization of conventional semibatch polyether polyol processes, in particular for the polymerization of propylene oxide to make polypropylene glycol, is addressed. A rigorous mathematical reactor model is first developed to describe the dynamic behavior of the polymerization process based on first‐principles including the mass and population balances, reaction kinetics, and vapor‐liquid equilibria. Next, the obtained differential algebraic model is reformulated by applying a nullspace projection method that results in an equivalent dynamic system with better computational performance. The reactor model is validated against plant data by adjusting model parameters. A dynamic optimization problem is then formulated to optimize the process recipe, where the batch processing time is minimized, given a target product molecular weight as well as other requirements on product quality and process safety. The dynamic optimization problem is translated into a nonlinear program using the simultaneous collocation strategy and further solved with the interior point method to obtain the optimal control profiles. The case study result shows a good match between the model prediction and real plant data, and the optimization approach is able to significantly reduce the batch time by 47%, which indicates great potential for industrial applications. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2515–2529, 2013     

Galacto-oligosaccharide production with immobilized β-galactosidase in a packed-bed reactor vs. free β-galactosidase in a batch reactor

We report here that the usage of immobilized enzyme in a continuous packed bed reactor (PBR) can be a good alternative for GOS production instead of the traditional use of free enzyme in a batch reactor. The carbohydrate composition of the product of the PBR with immobilized enzyme was comparable to that of the batch reactor with free enzyme. The stability of the immobilized enzyme at a lactose concentration of 38% (w/v) and at 50 °C was very high: the half-life time of the immobilized enzyme was approximately 90 days. The enzymatic productivity of GOS production using immobilized enzyme in a PBR can be more than six times higher than that of GOS production with free enzyme in a batch reactor. Besides, when aiming for an equal volumetric productivity to the batch process in designing a PBR, the volume of the PBR can be much smaller than that of the batch reactor, depending on the enzyme dosage and the run time of a single batch.     

Software for Simulation of Second‐Generation Ethanol Production by a Simultaneous Saccharification and Fermentation Process

Environmental impacts associated with the consumption of fossil fuels and the need to generate power through renewable resources demands the usage of alternative materials. The objective is the production of clean energy from materials like lignocellulosic biomass to produce second‐generation (2G) ethanol. A software in the Matlab program is elaborated to simulate the simultaneous saccharification and fermentation (SSF) process of lignocellulosic biomass for the 2G ethanol production in batch reactors. Studying the effects of the process variables, it was found that the higher interference is caused by cellulose concentration. Higher concentrations of the product in batch processes are obtained with the maximum cellulose concentrations, cells, and enzyme.     

CONCENTRATED ACID CONVERSION OF PINE SAWDUST TO SUGARS. PART II: HIGH-TEMPERATURE BATCH REACTOR KINETICS OF PRETREATED PINE SAWDUST

A study of high-temperature, concentrated-acid hydrolysis kinetics was undertaken for pretreated pine utilizing a corotating twin-screw extruder reactor. Five different acid concentrations were prepared ranging from 5 to 30 wt.% acid. These solutions were subjected to high-temperature acid hydrolysis at 110°, 120°, and 130°C using a custom-fabricated zirconium batch reactor. A number of nonlinear and linear regression analyses were undertaken so that the concentration of less resistant cellulose, resistant cellulose, glucose, and decomposition products could be obtained as a function of time, temperature, and acid concentration. Application of the kinetic rate constants obtained from the static batch reactor hydrolysis studies demonstrates that more than 50% of the theoretical glucose available in the pine sawdust can be obtained in roughly 25 minutes and 41% of the theoretical glucose available can be achieved in as little as 3 minutes. Further analysis highlights the importance of the pretreatment technique in achieving significant quantities of theoretical glucose in a short high-temperature reaction time.     

汽爆秸秆膜循环酶解耦合丙酮丁醇发酵

利用新型的汽爆玉米秸秆膜循环酶解耦合发酵系统进行了丙酮丁醇发酵的研究,并对使用该系统所导致的丙酮丁醇梭菌(Clostridium acetobutylicum AS1.132)代谢的变化进行了讨论. 在稀释率为0.075 h-1的条件下,丁醇的产量为0.14 g/g (纤维素+半纤维素),最大丁醇产率达到0.31 g/(L×h),溶剂组成为丁醇:丙酮:乙醇65.3:24.3:10.4(体积比),纤维素和半纤维素的转化率分别为72%和80%,使用单位纤维素酶所产生的丁醇量为3.9 mg/IU,是分步水解批次发酵的1.5倍. 利用该系统使酶解和发酵分别在各自最适的条件下同时连续进行,减少了纤维素酶的用量,有效地解除了酶解产物对纤维素酶的抑制作用,并减轻了溶剂产物尤其是丁醇对微生物活性的影响,延长了发酵周期.     

CONCENTRATED ACID CONVERSION OF PINE SAWDUST TO SUGARS. PART II: HIGH-TEMPERATURE BATCH REACTOR KINETICS OF PRETREATED PINE SAWDUST

A study of high-temperature, concentrated-acid hydrolysis kinetics was undertaken for pretreated pine utilizing a corotating twin-screw extruder reactor. Five different acid concentrations were prepared ranging from 5 to 30 wt.% acid. These solutions were subjected to high-temperature acid hydrolysis at 110°, 120°, and 130°C using a custom-fabricated zirconium batch reactor. A number of nonlinear and linear regression analyses were undertaken so that the concentration of less resistant cellulose, resistant cellulose, glucose, and decomposition products could be obtained as a function of time, temperature, and acid concentration. Application of the kinetic rate constants obtained from the static batch reactor hydrolysis studies demonstrates that more than 50% of the theoretical glucose available in the pine sawdust can be obtained in roughly 25 minutes and 41% of the theoretical glucose available can be achieved in as little as 3 minutes. Further analysis highlights the importance of the pretreatment technique in achieving significant quantities of theoretical glucose in a short high-temperature reaction time.     

Study on the enzymatic hydrolysis of racemic methyl ibuprofen ester

The hydrolysis of racemic methyl ibuprofen ester in the presence of lipase from Candida rugosa was investigated in shake flasks. Experiments were performed to study the effect of temperature, pH and shaking speed on the reaction rate. Different hydrophobic co‐solvents were screened for the highest reaction rate and the presence of enzyme inhibition by substrate and products was examined. A kinetic expression was then proposed to describe the reaction. Kinetic parameters were determined for the optimum operating conditions and the proposed model was verified with the experimental results. Next, this reaction was scaled up to a fed batch stirred tank reactor. Batch reactor and fed batch reactor configurations were compared for better conversions. The effects of aqueous phase hold‐up, substrate concentration and feed flow rate on the conversion of the reaction were also studied. Higher conversions were obtained in a fed batch reactor when compared with the batch reactor. In the fed batch reactor, increased conversions were observed with lower feed flowrates and high aqueous phase hold‐up. © 2001 Society of Chemical Industry     

Low-Temperature Dilute Acid Hydrolysis of Oil Palm Frond

Oil palm frond (OPF) fiber, a lignocellulosic waste from the palm oil industry, contains high cellulose and hemicellulose content, thus it is a potential feedstock for simple sugars production. This paper describes the two-stage hydrolysis process focusing on the use of low-temperature dilute acid hydrolysis to convert the hemicellulose in OPF fiber to simple sugars (xylose, arabinose, and glucose). The objective of the present study was to evaluate the effect of operating conditions of dilute sulfuric acid hydrolysis undertaken in a 1 L self-built batch reactor on xylose production from OPF fiber. The reaction conditions were temperatures (100–140°C), acid concentrations (2–6%), and reaction times (30–240 min). The mass ratio of solid/liquid was kept at 1:30. Analysis of the three main sugars glucose, xylose, and arabinose were determined using high-pressure liquid chromatography. The optimum reaction temperature, reaction time, and acid concentration were found to be 120°C, 120 min, and 2% acid, respectively. Based on the potential amount of xylose (10.8 mg/mL), 94% conversion (10.15 mg/mL) was obtained under the optimum conditions with small amount of furfural (0.016 mg/mL). To enhance the effectiveness of dilute acid hydrolysis, the hydrolysis of OPF fiber was also performed using ultrasonic-pretreated OPF fiber. The effects of ultrasonic parameters power (40–80%) and ultrasonication times (20–60 min) were determined on sugar yields under optimum hydrolysis conditions (2% acid sulfuric, 120°C and 120 min). However, the use of ultrasonication was found to have detrimental effect on the yield of simple sugars due to the 10-fold increase in the formation of furfural.     

有机相中固定化酶催化反应拆分手性化合物--间歇反应器内非定态动力学模拟

建立了有机相间歇反应器内球形多孔载体固定化酶催化反应拆分手性化合物的非定态动力学模型.采用正交配置法求解,讨论了对映体选择性E、内外传质阻力以及底物和水的抑制作用对酶促拆分手性化合物的拆分效果和速率的影响.结果表明:对映体选择性E是决定手性化合物能否拆分的关键参数;若一拆分过程对S-对映体优先反应,传质阻力可以忽略,E≥100,则R-和S-对映体几乎完全被拆分;如果存在传质阻力,则酶的对映体选择性降低,拆分效果不好,且拆分速率下降;底物和水的抑制作用对酶促拆分的效果影响不大,但拆分所需的时间相应增加.     

Tween80对稻草水解及同步糖化与发酵产乳酸的影响

在生物转化纤维原料产乳酸的过程中,酶解纤维原料产还原糖是限速步骤。为了获得较高的产物产率,需较高的酶用量,这使大规模酶解废弃纤维原料的成本很高。对吐温80在酶解稻草纤维素产糖,以及耐高温乳酸菌同步糖化发酵稻草产乳酸过程中的作用进行了考察。初步结果表明,吐温80加入可使保持同等程度的水解率所需的酶用量降低,添加0.2 g/g底物的吐温80到酶用量10 FPU/g体系,水解120 h的糖产率为292.2 mg/g,比不加表面活性剂体系的糖产率增加了11%;添加0.7 g/L的吐温80进行同步糖化与发酵72 h,能使乳酸产量提高24.2%。     

用于分布式制氢的甲烷蒸汽重整膜反应器的数值模拟

采用反应-分离集成的膜反应器进行分布式制氢,对简化工艺、降低能耗、提升技术经济性至关重要。本文采用数学模型对甲烷蒸汽重整制氢过程膜反应器进行模拟,系统分析了渗透侧操作策略、反应压力、反应温度、钯基膜性能、催化剂性能对反应器行为的影响;并以1m³/h甲烷最大程度转化为目标进行分布式制氢案例分析,详细比较膜反应器技术与“常规反应器+膜分离”工艺技术。结果表明,膜反应器在反应压力30atm（1atm=101325Pa）、反应温度500℃下操作可实现紧凑设计,比“常规反应器+膜分离”工艺技术具有明显优势,但是亟需研发更佳活性（10倍）的钯基膜和催化剂以实现显著的过程强化。模拟结果可为不同规模分布式制氢膜反应器的操作与设计及进一步的性能强化提供指导。     

Microbial oxidation of naphthalene to cis-1,2-dihydroxy-1,2-dihydronaphthalene in a membrane bioreactor

A microbial dihydroxylation process for the production of cis-1,2-dihydroxy-1,2-dihydronaphthalene from naphthalene is reported. The oxidation reaction was initially studied in a stirred tank reactor using resting cells of a Pseudomonas fluorescens mutant, grown on glucose as carbon source and acetyl salicylate as inducer of the naphthalene dioxygenase enzymatic system. In these conditions the productivity of the system was limited by the efficiency of the oxygenation and by a reversible product inhibition phenomenon. In order to overcome the inhibitory effect of the 1,2-dihydrodiol accumulation, the biotransformations were carried out in a stirred reactor equipped with a membrane ultrafiltration device. In this way, the cells and the insoluble naphthalene were retained and recycled into the vessel, while the soluble diol was continuously removed through the membrane permeate. The diol was recovered by selective adsorption on a column packed with an adsorbent resin, allowing the rapid and direct recycle of the reaction medium back to the enzymatic reactor. This system afforded a final yield three-fold higher than that of the batch process, exhibiting a bioconversion rate of 1·3 g h⁻¹ dm⁻³ for more than 16 h of continuous working.