Hydrolysis of liquefied corn starch in a membrane reactor

The objective of this study was to develop a continuous hydrolysis process for the enzymatic saccharification of liquefied corn starch using a membrane reactor. A residence time distribution study confirmed that the membrane reactor could be modeled as a simple continuous stirred tank reactor (CSTR). Kinetic studies indicated that the continuous reactor operated in the first-order region with respect to substrate concentration at substrate concentrations greater than 200 g/L. At a residence time of 1 h and an enzyme concentration of 1 g/L, the maximum reaction velocity (V(m)) was 3.86 g glucose/L min and the apparent Michaelis constant (K(m) (')) was 562 g/L. The K(m) (') value for the continuous reactor was 2-7 times greater than that obtained in a batch reactor.Kinetic data were fit to a model based on the Michaelis-Menten rate expression and the design equation for a CSTR. Application of the model at low reactor space times was successful. At space times of 6 min or less, the model predicted the reactor's performance reasonably well. Additional work on the detection and quantitation of reversion products formed by glucoamylase is required. Isolation, detection, and quantitation of reversion products by HPLC was difficult. Detailed analysis on the formation of these reversion products could lead to better reactor designs in the future.     

Kinetics on the turbidity change of wheat starch during its retrogradation

Wheat starch dispersions of 10–40% (w/w) were gelatinized and the change in turbidity of each solution during storage was measured in the 400–1100 nm wavelength range. The relative transmittance, defined as the ratio of transmittance at any storage time to that at the initial time, decreased when the solutions were stored at 5 and 30 °C; the decrease, reflecting the progress of retrogradation, was larger at 5 °C than at 30 °C. Most of the changes in relative transmission taking place over 14 days were achieved during the first 90 min. The change in the relative transmittance is inversely proportional to the energy required for deformation. The kinetics on change in relative transmittance can be expressed by Weibull equation. The larger rate constant at higher starch concentration could be ascribed to the state of the starch granules, which depended on starch concentration.     

响应面法优化米糠淀粉酶法水解工艺

以米糠为原料,对米糠淀粉酶法水解生产葡萄糖的液化工艺进行研究和优化,来提高葡萄糖收率。在单因素试验的基础上,用响应面法对液化工艺进行优化。结果表明,液化工艺的最佳条件为酶用量0.11%、醪浓度25%、pH=6.0、温度88℃,在此条件下得到的液化葡萄糖值(即DX值)平均值为6.54%。然后对此液化液进行糖化,最终得到的糖化液DX值为97.07%。     

Iteration model of starch hydrolysis by amylolytic enzymes.

An elaborate computer program to simulate the process of starch hydrolysis by amylolytic enzymes was been developed. It is based on the Monte Carlo method and iteration kinetic model, which predict productive and non-productive amylase complexes with substrates. It describes both multienzymatic and multisubstrate reactions simulating the "real" concentrations of all components versus the time of the depolymerization reaction the number of substrates, intermediate products, and final products are limited only by computer memory. In this work, it is assumed that the "proper" substrate for amylases is the glucoside linkages in starch molecules. Dynamic changes of substrate during the simulation adequately influence the increase or decrease of reaction velocity, as well as the kinetics of depolymerization. The presented kinetic model, can be adapted to describe most enzymatic degradations of a polymer. This computer program has been tested on experimental data obtained for alpha- and beta-amylases.     

Activities in Crude Porcine Pancreatic Lipase: Enantioselectivity in Hydrolysis of the Diacetate of 2-Phenylpropane-1,3-Diol

The hydrolysis of a prochiral diacetate by porcine pancreatic lipase is catalysed by the purified enzyme, not by an enzyme present in the crude enzyme but absent from the purified enzyme, as previously reported.     

Influence of photocrosslinking on the retrogradation of wheat starch based films

The ageing of wheat starch based materials was followed as a function of time for different systems suitably hydrated to be in the rubbery state. In particular, one aspect of retrogradation, that is to say the development of crystallinity is analysed in order to study the influence of a specific crosslinking treatment of starch films made by UV irradiation (photocrosslinking). Mechanical and thermal properties showed that an important limitation on this particular ageing occurs after photocrosslinking at room temperature. A process of accelerated ageing, monitored by modulated DSC, was also performed at 60 °C in order to increase retrogradation kinetics. The results showed a recrystallisation decrease and it appeared that the presence of the plasticiser enhances retrogradation. For a plasticised sample (17% glycerol), a decrease of 30% of the melting enthalpy was observed compared to 91% for an unplasticised one. A modification in the nature of the melting peaks, as recorded by modulated DSC, allowed us to propose a model for amylopectin retrogradation after crosslinking.     

Effects of acid hydrolysis and defatting on crystallinity and pasting properties of freeze-thawed high amylose corn starch

Paste of defatted and/or mildly acid-hydrolyzed high amylose corn starch was freeze-thawed, and then the starch was isolated by vacuum drying for the analysis in crystallization and pasting properties. X-ray diffraction pattern and differential scanning calorimetric analysis showed that the crystallinity of the freeze-thawed starch was increased as the degree of hydrolysis increased. The diffraction pattern revealed B- and V-crystals with patterns with diffraction peaks at 17, 20, and 23–25° (2θ), which were developed by amylose recrystallization during the freeze-thawing. The crystal melting enthalpies, for dual endothermic transitions above 100 °C, which resulted from the melting of amylose–lipids complex and amylose double helices were raised by the treatment. The isolated and dried starch formed a paste by aqueous heating under the ambient pressure, and its paste viscogram exhibited substantially higher resistance to shear-thinning, and rapid setback upon cooling. Acid hydrolysis, however, reduced overall paste viscosity, possibly due to the increased crystallinity. Enzyme-resistant starch content in the acid hydrolyzed starch was increased by the freeze-thawing, but not by acid hydrolysis. It was slightly increased by defatting.     

大豆分离蛋白不同酶解方式水解度与乳化性和起泡性关系

研究了大豆分离蛋白酶解产物水解度与乳化和起泡功能特性的关系。试验结果表明:大豆分离蛋白酶解产物起泡性随着水解度的增加而增加,不同酶处理液的起泡性以AS1.398酶解液最好,水解度为20%时起泡性达到了360±2.46%。研究还发现,乳化性随着水解度增加而逐渐下降,以双酶复合酶解液最差(DH=25%时乳化性最差,17.60±0.80m l.g-1)。     

A novel raw starch digesting thermostable α-amylase from Bacillus sp. I-3 and its use in the direct hydrolysis of raw potato starch

A new strain of Bacillus sp. I-3, isolated from natural soil samples, showed a high raw starch digesting activity towards potato starch. Upon optimization of various environmental and cultural conditions, the yield of α-amylase reached 642 U/mL. The kinetic characterization of partially purified enzyme exhibited the maximum activity at 70 °C, pH 7.0 and revealed a high thermostability in the presence of 10 mM CaCl₂·2H₂O where it could retain more than 90% residual activity at 70 °C after 3.5 h. At 80, 90 and 100 °C, the enzyme retained 80, 59 and 26% of its maximum activity after 2.5, 0.5 and 0.5 h, respectively. The enzyme preparation had a strong affinity towards raw potato starch granules and was almost completely adsorbed onto it. It also hydrolyzed raw potato starch at a concentration of 12.5% significantly in a short period of time of 12 h.     

Effect of water-soluble and insoluble non-starch polysaccharides isolated from wheat flour on the rheological properties of wheat starch gel

Water-soluble (WSP) and insoluble non-starch polysaccharides (WIP) were isolated from wheat flour to evaluate the effects of WSP and WIP on starch gel properties. Isolated WSP and WIP were added to two types of isolated wheat starch with different amylose content at a concentration of 3% based on the dry weight of starch. 30% starch gels were prepared and stored at 5 °C for 1, 8, or 24 h. The dynamic viscoelasticity of 30% starch gels mixed with WSP and WIP was measured using parallel plate geometry, showing that WSP and WIP affected the elastic component of starch gels in opposite ways. Adding WIP increased the storage shear modulus (G′) of starch gels, while adding WSP decreased G′ and dramatically increased the loss tangent (tan δ=G″/G′).     

白蜡虫卵蛋白酶解工艺的研究

本项目对白蜡虫(Ericerus pela)卵蛋白的酶解工艺进行了研究。通过正交试验确定木瓜蛋白酶为适宜的水解用酶,最佳用量为1.5%;酶解条件为酶解温度50℃,酶解pH值9.0,酶解时间24 h,原料与水比例为1∶20;试验结果还表明原料在酶解前经过预处理,蛋白水解率可提高20.7%,预处理条件为原料在20倍的1 mol/L盐酸溶液中,80℃恒温加热30 min;在确定的最佳条件下对白蜡虫卵进行预处理和酶解,蛋白水解率可达58.4%。     

Hydrolysis of crambe oil by enzymatic catalysis: An evaluation of the operational conditions

Abstract

In this work, the enzymatic hydrolysis of the crambe oil by using a commercial immobilized lipase Lipozyme RM IM was evaluated. The effect of the operational conditions, such as temperature, water/oil molar ratio, enzyme/substrate mass ratio and stirring speed were assessed based on the experimental designs. The experiments were performed in a closed and batch system with controlled temperature and stirring speed. In addition, the kinetics of the process was studied in the best operational conditions, wherein the experimental data were obtained and described by a mathematical model. The influence of the operational conditions was assessed based on the measured values of the free fatty acids (FFA) produced by the enzymatic hydrolysis. In 4?h of reaction, a yield of 42.6% was observed and the most significant operational conditions were the enzyme/substrate mass ratio and stirring speed. By the kinetic investigation, an initial reaction rate of 3.5?×?10⁴?mol?mL^?1?h^?1 and a maximum yield of 74% were observed after 40?h of reaction (in the equilibrium condition). The mathematical model was not only able to adequately describe the experimental data of FFA concentrations profiles but also showed predictive capacity to independents assays in different operational conditions. Therefore, based on the simulation analysis of the enzymatic hydrolysis of the crambe oil, the model can be useful for process optimization and phenomenological studies.     

Encapsulation of sunflower oil in starch matrices via extrusion: effect of the interfacial properties and processing conditions on the formation of dispersed phase morphologies

In this study, the encapsulation of sunflower oil in a starch matrix via extrusion was investigated. The aim of this study was to get insight into the relations between the processing parameters, the hydrophile–lipophile balance (or the hydrophobic–hydrophilic balance; HLB) value of the emulsifier and the morphology of the dispersed phase. The obtained samples were analysed for their dispersed phase morphology using scanning electron microscopy. It was seen that the HLB value of the emulsifier affected the dispersed phase morphology. The average size of the dispersed oil droplets decreased with increasing HLB value, and was explained by the observed decrease in the interfacial surface tension between the starch melt and the oil phase. Average sizes of oil droplets also decreased with increasing screw speed, increasing melt temperature and decreasing throughput. The screw configurations also affected the average sizes of dispersed oil droplets. Especially dispersive mixing elements and kneading blocks favour the formation of smaller dispersed oil droplets.     

Effect of substitution of wheat starch by potato starch on the performance,digestive physiology and health of growing rabbits

The goal of this research was to study the effect of the substitution of wheat starch by potato starch (PS) on the performance, health and digestion of growing rabbits. Three experimental diets were formulated with 0%, 7% and 14% PS (PS0, PS7 and PS14, respectively) and similar starch contents (22% dry matter basis), proteins and fibre. The three diets were administered to three groups of 48 rabbits from weaning (28 days) to slaughter (70 days), and growth and health measurements were made. Another 10 rabbits per diet (30 rabbits at each age), reared under similar conditions, were slaughtered at 6 to 10 weeks of age, and the digesta were collected to analyse the caecal microbial activity (pH, volatile fatty acids (VFA) levels, fibrolytic activity) and the starch concentration in the ileal digesta. At the same ages, the whole tract digestibility coefficients were measured in 10 other rabbits for each treatment (30 rabbits). The feed intake between 28 and 42 days of age (days) increased by 11% (P < 0.05) in PS0 v. PS14. Over the whole growth period (28 to 70 days), weight gain was similar among diets (40.5 g/day), whereas the feed intake and feed conversion increased (8.5% and 5.2%, respectively; P < 0.05) with the PS14 diet. Mortality and morbidity were not affected by the diets. The starch concentration of the ileal contents increased (P < 0.01) with the addition of PS to the diet (0.39%, 0.77% and 1.08% for diets PS0, PS7 and PS14, respectively). Starch digestibility was 0.8 percentage units higher (99.8% v. 99.0%) with the PS0 diet than the PS14 diet (P = 0.04). The bacterial cellulolytic activity in the caecum tended to be higher with the PS14 diet (P = 0.07). The total VFA caecal concentration increased (P < 0.01) only in 6-week-old rabbits with PS7 compared with PS0 (54.7 v. 74.5 mmol/l). Protein digestibility and ileal starch concentration decreased (P < 0.05) with age (6 v. 10 weeks), and hemicelluloses digestibility increased (P < 0.05). At 10 weeks of age, rabbits showed a higher VFA pool (6.25 mol) and proportion of butyrate (15.9%) and a lower proportion of acetate (79.3%), ammonia level (7.5 mmol/l) and C3/C4 ratio (0.31) than at 6 weeks of age. The intake of potato starch had no effect on the performance, caecal microbial activity or digestive health of growing rabbits.     

Adsorption characterisation of water and ethanol on wheat starch and wheat gluten using inverse gas chromatography

Adsorption of water and ethanol on wheat starch and wheat gluten has been studied in the temperature range of 60–150 °C using inverse gas chromatography (IGC). From the chromatographic retention data it is able to calculate the separation factors for the two solutes and obtain values for thermodynamic parameters such as Gibbs free energy (ΔG_s) and the enthalpy (ΔH_s) of adsorption of water and ethanol. The results indicate that water is adsorbed more strongly than ethanol at all temperatures, and the low temperature is found to facilitate the adsorptive separation of water from ethanol. It is also shown that the starch definitely plays a crucial role for the water and ethanol separation, despite that wheat flour includes both gluten and starch. The wheat starch is seen to have potential application in biomass water–ethanol separation to obtain fuel ethanol through the preferential adsorption of water from aqueous ethanol.     

On the effect of surface active agents and their structure on the temperature-induced changes of normal and waxy wheat starch in aqueous suspension. Part II: A confocal laser scanning microscopy study

The location and penetration patterns of two fluorescently labelled, surface active molecules into normal and waxy wheat starch granules prior, during and after the temperature-induced gelatinization were studied by means of confocal laser scanning microscopy (CLSM). Amphiphilic dyes were found to have a tendency to penetrate wheat starch granules in aqueous suspension. The penetration patterns were however found to be dependent on the contact time, type of starch and the chain length (C₁₂ vs. C₁₆) of the amphiphilic dye. The penetration of amphiphilic dyes through the starch granule matrix proved to be less restricted in waxy than in normal wheat starch. For a given type of starch, the penetration of the longer chain dye was more constrained than that of the shorter chain one. The extent to which the dye diffuses into the granule matrix as it gelatinizes is also affected by the chain length of the dye, diffusion of the shorter chain dye occurring more profusely and at lower temperatures than for the longer chain one. These differences are suggested to be related to the dissociation temperature of the AM-amphiphilic dye complexes.     

重组小麦静息巯基氧化酶的表达、酶学特性及其对面包品质的影响

为发展新型面粉改良酶制剂,利用大肠杆菌Escherichia coli原核表达了小麦静息巯基氧化酶(Wheat quiescin sulfhydryl oxidase,wQSOX)。将合成的wqsox基因构建至pMAL-c5x载体,并在大肠杆菌中进行表达,优化蛋白表达条件后对重组蛋白进行分离纯化及融合标签切除,获得的重组wQSOX蛋白用于酶学性质探究以及面包品质改良。结果表明,合成的截短wqsox基因包含1359 bp,编码453个氨基酸,理论蛋白分子量51 kDa;构建的pMAL-c5x-wqsox重组质粒在E.coli Rosetta gamiB(DE3)中可溶表达了重组蛋白MBP-wQSOX,其最佳表达条件为:诱导温度25℃,诱导剂IPTG浓度0.3 mmol/L,诱导时间6 h;利用Xa因子蛋白酶切除了MBP融合标签,亲和层析纯化得到了wQSOX;wQSOX可催化DTT、GSH和Cys氧化,并伴随着H2O2的生成,其中对DTT表现出最高的底物特异性;酶学性质研究发现,wQSOX最适反应温度和pH分别为50℃和10.0,在高温和碱性环境条件下表现出较好的稳定性;每克面粉中添加1.1 U wQSOX能够显著(P<0.05)提高26.4%的面包比容,降低20.5%的面包芯硬度和24.8%的咀嚼性,表现出了较好的改良面包加工品质能力。研究结果对丰富新型面粉改良酶制剂种类以及推动wQSOX在焙烤行业的应用奠定了理论基础。