Simultaneous saccharification and fermentation of wheat bran flour into ethanol using coculture of amylotic Aspergillus niger and thermotolerant Kluyveromyces marxianus

Studies on simultaneous saccharification and fermentation (SSF) of wheat bran flour, a grain milling residue as the substrate using coculture method were carried out with strains of starch digesting Aspergillus niger and nonstarch digesting and sugar fermenting Kluyveromyces marxianus in batch fermentation. Experiments based on central composite design (CCD) were conducted to maximize the glucose yield and to study the effects of substrate concentration, pH, temperature, and enzyme concentration on percentage conversion of wheat bran flour starch to glucose by treatment with fungal α-amylase and the above parameters were optimized using response surface methodology (RSM). The optimum values of substrate concentration, pH, temperature, and enzyme concentration were found to be 200 g/L, 5.5, 65°C and 7.5 IU, respectively, in the starch saccharification step. The effects of pH, temperature and substrate concentration on ethanol concentration, biomass and reducing sugar concentration were also investigated. The optimum temperature and pH were found to be 30°C and 5.5, respectively. The wheat bran flour solution equivalent to 6% (w/V) initial starch concentration gave the highest ethanol concentration of 23.1 g/L after 48 h of fermentation at optimum conditions of pH and temperature. The growth kinetics was modeled using Monod model and Logistic model and product formation kinetics using Leudeking-Piret model. Simultaneous saccharificiation and fermentation of liquefied wheat bran starch to bioethanol was studied using coculture of amylolytic fungus A. niger and nonamylolytic sugar fermenting K. marxianus.     

厌氧发酵生产丁二酸的动力学模型

引言 丁二酸(butanedioic acid)作为C4平台化合物,可以用于合成1,4-丁二醇、四氢呋喃、γ-丁内酯等有机化学品以及聚丁二酸丁二醇酯(PBS)类生物可降解材料,被美国能源部认为是未来12种最有价值的生物炼制产品之一.     

Simultaneous saccharification and fermentation of wheat bran flour into ethanol using coculture of amylotic Aspergillus niger and thermotolerant Kluyveromyces marxianus

Studies on simultaneous saccharification and fermentation (SSF) of wheat bran flour, a grain milling residue as the substrate using coculture method were carried out with strains of starch digesting Aspergillus niger and nonstarch digesting and sugar fermenting Kluyveromyces marxianus in batch fermentation. Experiments based on central composite design (CCD) were conducted to maximize the glucose yield and to study the effects of substrate concentration, pH, temperature, and enzyme concentration on percentage conversion of wheat bran flour starch to glucose by treatment with fungal α-amylase and the above parameters were optimized using response surface methodology (RSM). The optimum values of substrate concentration, pH, temperature, and enzyme concentration were found to be 200 g/L, 5.5, 65°C and 7.5 IU, respectively, in the starch saccharification step. The effects of pH, temperature and substrate concentration on ethanol concentration, biomass and reducing sugar concentration were also investigated. The optimum temperature and pH were found to be 30°C and 5.5, respectively. The wheat bran flour solution equivalent to 6% (w/V) initial starch concentration gave the highest ethanol concentration of 23.1 g/L after 48 h of fermentation at optimum conditions of pH and temperature. The growth kinetics was modeled using Monod model and Logistic model and product formation kinetics using Leudeking-Piret model. Simultaneous saccharificiation and fermentation of liquefied wheat bran starch to bioethanol was studied using coculture of amylolytic fungus A. niger and nonamylolytic sugar fermenting K. marxianus.     

Kinetic modeling of gamma-aminobutyric acid production by Lactobacillus brevis based on pH-dependent model and rolling correction

Gamma-aminobutyric acid (GABA) is a natural non-protein functional amino acid, which has potential for fermentation industrial production by Lactobacillus brevis. This work investigated the batch fermentation process and developed a kinetic model based on substrate restrictive model established by experimental data from L₂₅(5⁶) orthogonal experiments. In this study, the OD₆₀₀ value of fermentation broth was fixed to constant after reaching its maximum because the microorganism death showed no effect on the enzyme activity of glutamate decarboxylase (GAD). As pH is one of the key parameters in fermentation process, a pH-dependent kinetic model based on radial basis function was developed to enhance the practicality of the model. Furthermore, as to decrease the deviations between the simulated curves and the experimental data, the rolling correction strategy with OD₆₀₀ values that was measured in real-time was introduced into this work to modify the model. Finally, the accuracy of the rolling corrected and pH-dependent model was validated by good fitness between the simulated curves and data of the initial batch fermentation (pH 5.2). As a result, this pH-dependent kinetic model revealed that the optimal pH for biomass growth is 5.6-5.7 and for GABA production is about 5, respectively. Therefore, the developed model is practical and convenient for the instruction of GABA fermentation production, and it has instructive significance for the industrial scale.     

放射型根瘤菌分批发酵生产辅酶Q10的代谢特性和发酵动力学

以放射型根瘤菌WSH2601作为辅酶Q10分批发酵的试验菌,对其代谢特性进行了初步研究。对分批发酵过程中细胞生长、产物积累、糖消耗、中间产物有机酸及pH的变化规律进行了描述：由Logistic模型方程分别建立了放射型根瘤菌辅酶Q10发酵过程细胞生长、产物合成及基质消耗随时间变化的数学模型。模型模拟计算结果与实验值能较好地吻合。动力学研究结果表明该模型能较好地反映放射型根瘤菌的细胞生长、底物消耗和产物合成过程及其动力学机制。辅酶Q10分批发酵中细胞生长与产物合成属于半偶联型。     

辅酶Q10的发酵动力学

在5 L发酵罐实验数据基础上,应用Logistic方程基于Agrobacterium tumefaciensATCC4452(根癌农杆菌)菌种的生长、辅酶Q10的产量、底物的消耗、生物量的形成和维持创建动力学模型。应用MATLAB 7.0软件经非线性拟合和优化,获得了最佳的模型参数值,确定了菌体最大比生长速率为0.105 h-1和较大的生物量对辅酶Q10的得率系数YP/X=2.445 5,拟合模型R2均大于0.996,结果显示模型与实验数据能较好地吻合,确定了细菌合成辅酶Q10分批发酵过程的动力学特征。     

Development of a mathematical model for Bacillus circulans growth and alkaline protease production kinetics

BACKGROUND: An unstructured mathematical model was developed to understand information on the relationship between Bacillus circulans growth and metabolism‐related protease production (using logistic and Luedeking–Piret equations respectively) in a batch reactor with respect to glucose consumption and fermentation time. The objective was to develop an indispensable tool for the optimisation, control, design and analysis of alkaline protease production. RESULTS: Biomass growth and enzyme production titres changed with a change in substrate concentration. Modelling analysis of biomass and enzyme production titres at different substrate concentrations revealed significant accuracy in terms of statistical consistency and robustness with respect to fermentation kinetic profiles. CONCLUSION: With the B. circulans strain used, an economic protease yield (2837 × 10³ U g^?1) with respect to biomass and glucose ratio was achieved at low substrate concentration (10 g L^?1). The developed model could be effectively utilised for designing, controlling and up‐scaling the protease production process in high‐density fermentation in selected bioreactors with statistical consistency. Copyright © 2008 Society of Chemical Industry     

白色链霉菌分批发酵ε-聚赖氨酸的动力学分析

发酵过程动力学分析是实现发酵过程优化与控制的关键因素之一.通过运用Sigmoid模型,对白色链霉菌生产ε-聚赖氨酸的分批发酵过程进行分析,拟合得出底物消耗、菌体生长和产物形成的动力学方程,模拟得到的动力学曲线与试验值相符,可为ε-聚赖氨酸生产的分批发酵法和补料分批发酵法提供理论依据.     

ETHANOL FERMENTATION OF MIXED GLUCOSE AND XYLOSE BY PICHIA STIPITIS

Pichia stipitis CBS 5773 yeast cells were used to ferment the mixed substrates consisted of glucose andxylose to produce ethanol.The effects of aeration rate,initial substrate concentration and pH on substrateutilization and ethanol yield were evaluated.During batch fermentation,the oscillation phenomena in cell growthwere observed at low aeration rate,whereas the diauxic growth at high aeration rate.The substrate utilizationratio and ethanol yield reached 95％ and 0.46g/g respectively under appropriate operation conditions.Amodified unstructural model was proposed to simulate the diauxic cell growth,substrate consumption andproduct formation.     

Kinetics of lactic acid fermentation on glucose and corn by Lactobacillus amylophilus

The biosynthesis of ammonium lactate, a product of lactic acid fermentation was studied from corn and glucose at five different pH values of 5.4 to 7.8. In the glucose fermentations, a 100% conversion of substrate was obtained resulting in a maximum lactic acid production yield of 93.2%. The optimum pH for the maximum volumetric rate of lactic acid biosynthesis (1.56 g dm^?3 h^?1) was between 6.0 and 6.5. The corn fermentations were slower than the glucose fermentations with a resulting lactic acid yield of 67.5%. Hydrolysis of corn by enzymatic or chemical methods as well as the use of ammonium hydroxide for pH control increased both the final concentration and the rates of lactic acid production. An enhanced yield of more than 90% was finally obtained in the corn fermentations. A logistic model adequately described the kinetics of biomass growth, lactic acid production and sugar utilization in the glucose fermentations at different pH values. The dynamics of lactic acid formation in the corn fermentations were also successfully described by the developed model. The dependence of the model parameters on pH was investigated.     

A model of sugar utilisation during batch beer fermentation

A mathematical model describing the kinetics of sugar utilisation and changes in active yeast concentration during batch fermentation of brewers' wort is presented. Consideration is first given to the problems of modelling multiple substrate systems in which microorganisms can utilise carbohydrates both simultaneously and sequentially. Ideas outlined in the introductory sections are then used to develop a model of the beer fermentation process, and it is shown how the model can be matched to experimental data.     

蔗糖、乳酸及KH2PO4对乳链菌肽合成的影响

在恒pH、厌氧条件下,研究了蔗糖、乳酸及KH2PO4对L. lactis sp. lactis ATCC11454分批发酵中细胞生长和乳链菌肽合成的影响. 乳链菌肽的合成表现为初级代谢动力学特征. 蔗糖对乳链菌肽的合成具有调控作用,提高蔗糖浓度可以提高细胞浓度及乳链菌肽效价,但过高的蔗糖浓度(>30 g/L)抑制了乳链菌肽的合成. 乳酸作为代谢产物抑制了菌体的生长,同时导致乳链菌肽效价的下降,乳链菌肽对菌体的得率系数YN/X随起始乳酸浓度的增加而减小,表明乳酸对乳链菌肽合成的影响更大. KH2PO4在恒pH条件下对乳链菌肽的合成并没有促进作用.     

Production of L‐lactic acid by Lactobacillus delbrueckii in chemostat culture using an ion exchange resins system

L ‐Lactic acid production from beet molasses by Lactobacillus delbrueckii CECT 286 in a continuous fermenter‐ion exchange resins system has been investigated and compared with that observed in a conventional chemostat. The principle of this method is to remove the lactate during the course of fermentation as it is formed by adsorption to an anion exchange resin (Amberlite IRA‐420) in the carbonate form and to overcome its inhibitory effects on lactic acid bacteria by maintaining low lactate concentrations in the medium. Ammonium lactate was formed by percolating ammonium carbonate solution through this resin and it was converted to lactic acid by treatment with a cation exchange resin (Amberlite IR‐120) in hydrogen form. Compared with a conventional chemostat, this fermentation–ion exchange resins system enhanced the fermentation, controlled the pH, and showed the remarkable effect of increasing the yields of lactic acid from sucrose and biomass from sucrose due to the complete utilization of sucrose. © 1999 Society of Chemical Industry     

Hydrolysis and solubilization of corn gluten by Neutrase

Hydrolysis and solubilization of corn gluten were performed using a commercial protease preparation Neutrase. The effects of substrate concentration, enzyme concentration, temperature, pH and hydrolysate amount on the degree of hydrolysis and solubility of corn gluten were investigated depending on processing time. Trials were conducted in a batch reactor and degrees of hydrolysis were computed using a pH‐stat method. Results show that solubility and degree of hydrolysis were almost linearly related in all process conditions applied except in the case of hydrolysate addition. Optimum conditions for hydrolysis and solubilization were obtained as 10 g L^?1 protein concentration, 4 mL L^?1 enzyme concentration, 45 °C and pH 6.5. The mechanism of the kinetics was explained by taking into consideration association binding between the enzyme and substrate. The kinetics of hydrolysis and solubilization for all experiments performed were represented by exponential association equations that have not been used in the literature before. Also, to illustrate the effect of process variables on hydrolysis and solubilization, some modelling studies were performed. Copyright © 2007 Society of Chemical Industry     

Kinetics of Lactic Acid Fermentation by Lactobacillus delbrueckii Grown on Beet Molasses

The fermentation kinetics for the conversion of beet molasses, a valuable and economical fermentation substrate, to lactic acid by the homofermentative organism Lactobacillus delbrueckii C.E.C.T. 286 have been studied at controlled pH and temperature under anaerobic batch conditions. An inhibitory effect of lactic acid on fermentation of beet molasses has been found. The bacterium was able to produce lactic acid even after growth ceased. A kinetic model for the fermentation is proposed. From this model, the maximum allowable lactic acid concentration above which growth stops and the lactic acid level above which bacteria stop producing lactic acid were found to be 45 g dm⁻³ and 57 g dm⁻³, respectively. © 1997 SCI.     

天蓝色链霉菌产蓝色素的分批发酵动力学分析

在分批发酵中，研究了天蓝色链霉菌的生长、基质消耗及蓝色素分泌的特性. 基于Logistic方程和Luedeking-Piret方程，得到了描述分批发酵过程的动力学模型及模型参数，同时对实验数据与模型进行了验证比较. 模型计算值与实验数据拟合良好，模型基本反映了天蓝色链霉菌分批发酵过程的动力学特征.     

MATHEMATICAL MODEL OF L-LACTIC ACID FERMENTATION IN A RDC COUPLED WITH PRODUCT SEPARATION BY ION EXCHANGE

A Rotating Disk Contactor (RDC) was designed to perform the L-lactic acid fermentation with a filamentous fungus, Rhizopus oryzae, which was immobilized on the surface of rotating disks. The bioreactor was operated in repeated batch or continuous modes. The growth rate of the fungi was about 1 mm/day perpendicular to the disks' surface. A weak-base anionic resin, D354, was selected which was high in selectivity for lactic acid separation. Even at low concentration, the ion exchange capability was about 0.5 g Lac/g dry resin. A coupled process of L-lactic acid fermentation and ion-exchange separation was evaluated experimentally. The results indicated that the pH value of the fermentation broth could be maintained at pH 3.5 without any addition of alkali. The conversion ratio of glucose to L-lactic acid was about 0.7 g/g and the fermentation rate was able to reach as high as 62.5g glucose per hour per square meter of the disk surface area. A mathematical model was proposed to describe the simultaneous process of L-lactic acid fermentation and separation by ion exchange, in which the thickness increase of mycelia as well as the substrate and product inhibitions were included. The model simulation was in good agreement with the experimental data.     

Statistical optimization of fermentation conditions for the improved production of poly-β-hydroxybutyrate from Bacillus subtilis

Poly-β-hydroxybutyrate (PHB) has been an effective biodegradable plastic obtained by microbial fermentation. Batch fermentation of Bacillus subtilis features an attractive system for the production of PHB. Identification of appropriate media components and cultivation conditions are extremely important for the optimal production of biomass and/or PHB production. Statistical media design was utilized for the optimization of different fermentation variables (glucose, peptone, sodium chloride, K₂HPO₄, KH₂PO₄, ammonium sulfate, ammonium chloride, sodium sulfate, temperature, inoculum size, and pH). The optimized media predicted the optimal dry cell weight of 7.54?g?L^?1 and PHB production of 77.2?mg?L^?1 at 1?g?L^?1 of peptone, 1.46?g?L^?1 sodium sulfate, and pH 6.8 in 24?h. Glucose utilization, batch growth, and PHB production kinetics of B. subtilis were determined experimentally. The effect of substrate inhibition on specific growth rate was also determined experimentally for B. subtilis. The values of kinetic and substrate inhibition parameters obtained from this study shall be utilized to develop a mathematical model for PHB production for further improving the production of PHB.     

沙雷氏菌Serratia sp.BK-98发酵生产2-酮基-D-葡萄糖酸的工艺优化及动力学研究

引言 2-酮基-D-葡萄糖酸(2-KDG)有着广泛的用途,它能被用作食品添加剂、水泥增塑剂、洗涤剂,是照片显影剂的重要成分[1];同时它也是除草剂[2]、D-核酮糖、D-阿拉伯糖,特别是D-异抗坏血酸合成过程中的重要前体.     

沙雷氏菌Serratia sp.BK-98发酵生产2-酮基-D-葡萄糖酸的工艺优化及动力学研究

Based on the optimization of culture conditions for producing 2-keto-D-gluconic acid(2-KDG)by Serratia sp.BK-98 in a Erlenmeyer flask, the factors of dissolved oxygen(DO)and pH affecting 2-KDG batch fermentation in 100 L fermenter were further optimized to be 30% and 6.0 respectively.Under the DO-stat and pH-stat batch culture conditions, 2-KDG production reached 211.2 g·L^-1.The kinetics of DO-stat and pH-stat batch fermentation were also investigated and the models for biomass, substrate consumption and product were established respectively based on the Logistic equation, Leudeking-Piret equation and Modified Leudeking-Piret equation.Curve fittings for the above models by using experimental data were performed by the non-linear least squares method with the software Origin 8.0.With the evaluated model parameters, the calculated values of the models and experimental data were in good agreement and the models could provide guidance for 2-KDG fermentation production.