Steady states of a biotechnological process for producing lactic acid at a given dilution rate

Conditions are determined that ensure the presence of steady states in a continuous biotechnological process for producing lactic acid. The possibility of implementing multiplicity depending on the kinetic parameters and the inlet values of the characteristics of the synthesis process is shown. An algorithm is developed for evaluating the multiplicity of steady states and calculating the characteristics of the process under the conditions of multiplicity.     

Modeling the continuous biotechnological process of lactic acid production

The results of the mathematical modeling of a continuous biotechnological process for producing lactic acid are considered. The model is based on the Luedeking-Piret kinetic equation, which includes the concepts of the maximum specific rates of biomass growth, substrate consumption, and product formation. The possibility of the existence of optimum conditions for productivity with respect to the target product and the possibility of the existence of a multiplicity of steady states that ensure the same value of productivity are shown. An algorithm is described for calculating the characteristics of the process for different concentrations of a substrate in the inlet stream and different dilution rates.     

Mathematical modeling of biotechnological process of lactic acid production by batch fermentation: A review

The results of analyzing mathematical models of the process of batch fermentation for the production of lactic acid have been presented. Three groups of mathematical models have been considered. The first two groups are based exclusively on the notion of the specific growth rate, dependent or independent on substrate concentration. The third group uses the notions of the specific rate of substrate consumption and specific rate of product formation in additions to the notion of specific growth rate. The numeric estimates of constants are presented for the majority of models as well as comparison with the experimental studies. Mathematical models of the processes where the formation of side products is possible have been discussed, which may or may not be of value on their own. The possible practical applicability of the models has been evaluated based on the results of the analysis.     

Formation of the stream of liquid at the inlet to a spinneret hole

Conclusions Investigation of the formation of a stream of liquid at the entrance to a spinneret hole has shown that the size of the disturbing zone in the reservoir and the profile of liquid flow velocity at the entrance to the capillary depend on the Reynolds number and the rheological properties of the liquid.When Re<1, rearrangement of the stream velocity fields in the initial section of the capillary takes place identically for all values of the mean velocity and viscosity of the liquid, and the length of thehydrodynamic stabilization section for lengthwise stream velocity depends basically on the radius of the reservoir. When Re>10, the length of the hydrodynamic stabilization section depends only on the Reynolds number.The formation and magnitude of the stagnant zones at channel angles depends on the Reynolds number for Newtonian liquids, but for anomalously viscous liquids, it depends, even directly, on the mean velocity of the stream of liquid.Translated from Khimicheskie Volokna, No. 1, pp. 44–46, January–February, 1986.     

氯乙酸的间歇式与连续化生产工艺比较

比较了国内氯乙酸间歇式生产工艺和国外连续式生产工艺,提出了宜采用连续式生产工艺的建议。     

Design of a continuous process for the alkaline treatment of xylose into lactic acid

A compact process based on a gas/liquid contactor was designed for the continuous alkaline oxidation of xylose into lactic acid. An experimental design using Doehlert's method was used to study the effect of: i) the NaOH concentration, ii) the xylose concentration, iii) the reaction temperature, and iv) the residence time, on the yield of lactic acid. Results indicate that the conversion of xylose at concentrations between 5-15% (w/w) is complete and nearly instantaneous at both high temperatures (over 200°C) and high sodium hydroxide concentrations ((> 10% w/w). Yields of lactic acid reaching 50% (with a theoretical yield of 60% (w/w)) were obtained under the most favorable experimental condition suggested by the model developed.     

A continuous process for the recovery of lactic acid by reactive distillation

Separation and purification of lactic acid from the fermentation broth are difficult because of its non‐volatile nature and the presence of other organic acids. Esterification of lactic acid with methanol followed by hydrolysis of the separated methyl lactate is an effective technique for this purpose. A continuous process for recovery is proposed and various aspects are evaluated through simulation and experiments. In the proposed route, a vapor stream containing methyl lactate is removed from a two‐phase CSTR, used for esterification, operated under boiling conditions. The ester thus separated from the aqueous solution is further hydrolyzed in a reactive distillation column. Continuous removal of the volatile component (i.e. methanol) from the reaction zone increases conversion, thus pure lactic acid is obtained from the bottom of reactive distillation column. The results obtained in the experiments are compared with the simulation results. Further simulation studies were performed to obtain the suitable operating conditions for higher conversion and concentration of lactic acid. Copyright © 2006 Society of Chemical Industry     

Theoretical analysis of inhibition effect on steady states of enzymatic membrane reactor with substrate and product retention for reaction producing weak acid

The aim of this study is to formulate a model of enzymatic membrane reactor (EMR), i.e., a continuous, stirred tank bioreactor with full enzyme recycle, for a reaction producing a weak acid, and to explore the effect of substrate and product inhibition of different mechanisms coupled with transport properties of the membrane on the static behaviour of the system. The inhibition of an enzyme by a substrate leads to the non-monotonicity of reaction rate expression with respect to the substrate concentration. If a product of enzymatic reaction, taking place in the EMR, influences the pH of a reaction mixture this is also the factor causing the non-monotonicity of the substrate and product dependent reaction rate. The character of these dependencies affects substantially the structure of the steady states of the reactor. The bifurcation diagrams, shown in the work, are of different characters depending on the bifurcation parameter. It has been found, that bifurcation diagrams for competitive and uncompetitive inhibition by a substrate differ in the number and position of bifurcation points. Steady states of multiplicity five have been localised in case of uncompetitive inhibition by the substrate at high affinity of the enzyme to this substrate. Retention of reagents, related to transport properties of a membrane, influences significantly the effectiveness of a process. A specially written software in Delphi™ has been used for the calculations.     

Use of sweet sorghum juice for lactic acid fermentation: preliminary steps in a process optimization

BACKGROUND: Lactic acid has many applications in the chemical industries and it can be produced economically by microorganisms using biomass raw materials of different origins. Sweet sorghum juice is a high sugar content raw material with potential for lactic acid production because after hydrolysis of its sucrose content the remaining glucose and fructose can supply the carbon demand of most lactic acid bacteria. However, satisfying the nitrogen and B‐vitamin needs of the bacteria by supplementation with yeast extract and/or other alternative nitrogen‐containing supplements can make the process too expensive. RESULTS: Using a statistical optimization process much of the yeast extract can be replaced by a cheaper alternative nitrogen source, namely wheat gluten. This resulted in a fermentation with 99% lactic acid yield and 3.04 g L^?1 h^?1 volumetric productivity. CONCLUSION: Using response surface methodology (RSM) media optimization was performed for lactic acid fermentation with an industrially acceptable result, reducing the costs of raw materials by half, replacing yeast extract by an alternative nitrogen source and applying yeast extract only as a source of micro‐elements (vitamins, salts, etc.) Copyright © 2010 Society of Chemical Industry     

Role of pH-regulation in lactic acid fermentation: Second steps in a process improvement

Lactic acid has versatile application in chemical industries and it can be economically produced from biomass resources, for example from sweet sorghum juice, containing easily fermentable sugars in high concentration (150-180 gL⁻¹). To neutralize the produced lactic acid, alkali addition (i.e., titration) or pH buffering was applied to avoid the inhibitory effect of the undissociated lactic acid. However, such a high concentration of ionized lactate also inhibits the growth and further production. Our task was to find an appropriate pH regulation method and to describe pH dependency of the used strain. Five pH regulation agents were tested and among them trimethylamine gave the best productivity result (3.13 gL⁻¹ h⁻¹), but considering technological aspects (such as dilution) ammonium hydroxide is also recommended. Titration by NH₄OH and buffering by CaCO₃ were compared, and then combined, resulted in very good productivity (3.55 gL⁻¹ h⁻¹). pH dependence of the used strain was also examined and the optimal pH value was between 6.8 and 7.0.     

烷基化废酸制备硫酸铵的新工艺方法

国内的烷基化装置主要以硫酸法为主,但烷基化废酸较难处理,其中以废酸生产硫酸铵的工艺比较成熟,但存在诸多问题。为降低能耗,提高效率,文中介绍了一种烷基化废酸制备硫酸铵的新工艺方法。以废硫酸与液氨为原料,以气升式浮选装置进行反应产物与聚合油分离,使用活性碳吸附塔脱色脱臭,蒸发结晶系统进行结晶。工艺在硫酸铵近饱和条件下生产,使用中和反应生成的热蒸汽为液氨汽化及硫酸铵结晶工序提供热量,实现能量集成。工艺得到的硫酸铵产品颜色纯白,品相较好,氮质量分数达20.80%,满足市场要求。使用流程模拟软件ASPEN对节能效果进行模拟计算,2万t/a处理量的项目可节约低压蒸汽1.9万t/a。工艺平均每处理1 t废酸净收益400元,经济效益显著。     

磷酸浓缩过程中的脱氟研究

采用强制循环蒸发系统进行磷酸浓缩过程中的脱氟研究,通过加入含SiO2的物质来增强磷酸脱氟效果。考察了浓缩出口磷酸浓度、酸循环流量、脱氟剂及其添加量对磷酸浓缩过程中脱氟效果的影响。结果发现:实验所用脱氟剂中较好的是硅藻土,脱氟剂适宜添加量约为100%理论量;系统酸循环流量的变化对脱氟效果影响较小;磷酸脱氟率正相关于出口磷酸浓度,当出口磷酸w(P2O5)约为55.1%时,磷酸脱氟率约为88.6%。     

半水-二水湿法磷酸装置结晶槽游离硫酸根的稳定控制

以进出物料平衡为出发点,分析导致结晶槽游离硫酸根波动的各种原因,从中找出稳定控制硫酸根的对策,最终达到制取易于过滤和洗涤的半水物晶体的目的。     

Steady states of the surface of a nonadiabatic flame near the limits

Within the framework of a weakly linear model, which describes a nonadiabatic flame near the limit of its propagation caused by heat losses, steady states of the combustion-wave from are studied. Three-dimensional structures of the wave front are formed because of diffusion-thermal instability of the planar flame. The limits of propagation of a curved flame front are shown to expand if the diffusion-thermal instability is taken into account: a cellular flame can exist at heat losses higher than the critical value for the two-dimensional flame. The stability of steady solutions, which describe the cellular flame near the limits of its propagation, is studied. For sufficiently high heat losses, steady solutions for a nonadiabatic flame with front discontinities are obtained. Translated fromFizika Goreniya i Vzryva, Vol. 35, No. 4, pp. 3–11, July–August 1999.     

Developing a process for producing ethylacetate via the dehydrogenation of ethanol

This work is devoted to developing a domestic process for the catalytic dehydrogenation of ethanol into ethylacetate, a product that is widely used as a solvent in the production of paint-and-lacquer materials, medicinal substances, and printing ink dyes for the food industry. The process is an alternative to the conventional method for producing of ethylacetate via the esterification of acetic acid with ethanol. In our process, ethanol (bioethanol) is the only raw material. Compared to the traditional technique, our process is nearly wasteless with respect to the raw material despite its reversibility and produces no harsh media or waste water. Ethanol is dehydrogenated into ethylacetate on NTK industrial catalysts (OOO Dorogobuzh, Russia) with different chemical composition. The catalysts are tested in a flow unit within a range of temperatures of 230–300°C and pressures of 0.1–2.0 MPa. The NTK-4 catalyst yields the best results: it allows the single-pass conversion of ethanol from 40 to 63% at a process selectivity of 86–94%. The NTK-4 catalyst exhibits stable operation and reproducibility of results under the conditions of laboratory tests, and the process is intended for tests in a pilot unit. The process could be of interest to low-capacity enterprises that are not equipped to operate with sulfuric acid using the conventional method and are engaged in the fields of solvents, the paint and lacquer industry, and packing materials.     

Effects of operation variables on the recovery of lactic acid in a batch distillation process with chemical reactions

In this study, the feasibility of recovery of lactic acid by batch reactive distillation using cation exchange resin as a catalyst was investigated. For the recovery of lactic acid, two reactions, esterification and hydrolysis, are involved and hence, an apparatus with two distillation columns was developed and operated in a batch mode to ensure enough residence time in the reboiler and column. The effects of operation variables such as catalyst loading, reactant mole ratio, feed concentration, type of alcohols and partial condenser temperature on the yield were studied. In this study, the reaction products of the esterification (methyl lactate and water) were distilled to the hydrolysis part to be recovered into pure lactic acid. The yield of lactic acid increased as catalyst loading in the esterification part increased and reactant mole ratio and feed lactic acid concentration decreased. Methanol as a reactant gave higher yield than any other alcohols. The yield of recovered lactic acid was as high as 90%. The yield of lactic acid was closely related to the boiling temperature of the reaction mixture in the esterification part     

Removal of TEX vapours from air in a peat biofilter: influence of inlet concentration and inlet load

This paper presents the results of the study of the removal of toluene, ethylbenzene, and o‐xylene (TEX) by biofiltration using a commercial peat as filter‐bed material. Runs with a single organic compound in air, and with the mixture of TEX in air, were carried out for at least 55 days in laboratory‐scale reactors inoculated with a conditioned culture. The influence of organic compound inlet load and of gas flow rate on the biofilter's performance was studied, including relatively high values of pollutant inlet concentration (up to 4.3 gC m^?3 for ethylbenzene, 3.2 gC m^?3 for toluene, and 2.7 gC m^?3 for o‐xylene). Results obtained show maximum elimination capacities of 65 gC m^?3 h^?1 for o‐xylene, 90 gC m^?3 h^?1 for toluene, and 100 gC m^?3 h^?1 for ethylbenzene, and high removal efficiency (>90%) even for moderately elevated concentrations: 3.0, 2.5 and 1.8 gC m^?3 for ethylbenzene, toluene and o‐xylene, respectively. The behaviour of the TEX mixture was in good agreement with the results obtained for the runs in which only one organic compound was present. Ethylbenzene and toluene are degraded easier than o‐xylene, and inhibitory effects due to the presence of multiple substrates were not observed. Copyright © 2005 Society of Chemical Industry     

Strain isolation and optimization of process parameters for bioconversion of glycerol to lactic acid

BACKGROUND: The crude glycerol from biodiesel production represents an abundant and inexpensive source which can be used as raw material for lactic acid production. The first aim of this investigation was to select a strain suitable for producing lactic acid from glycerol with a high concentration and productivity. The second aim was to obtain the optimum fermentation conditions, as a basis for large‐scale lactate production in the future. RESULTS: Eight bacterial strains, which could aerobically convert glycerol to lactic acid, were screened from soil samples. One of the strains, AC‐521, which synthesized lactic acid with a higher concentration, was identified based on its 16S rDNA sequences and physiological characteristics. These results indicated that this strain was a member of Escherichia coli. The optimal fermentation conditions for Escherichia coli AC‐521 were 42 °C, pH 6.5, 0.85 min^?1 (K_La). CONCLUSION: Escherichia coli AC‐521 suitable for producing lactic acid from glycerol with high concentration and productivity was identified. After 88 h of fed‐batch fermentation, both the lactic acid concentration and glycerol consumption reached maximum, giving 85.8 g L^?1 of lactic acid with a productivity of 0.97 g L^?1 h^?1 and a yield of 0.9 mol mol^?1 glycerol. Copyright © 2009 Society of Chemical Industry     

网络丝生产工艺探讨

用HEBERLEINP2 12网络喷嘴 ,在法国ICBTFTF12E3加弹机上生产不同网络度和牢度的网络丝。探讨了网络张力、压缩空气压力等工艺条件与网络度和牢度的关系 ;优化工艺参数 ,生产的网络丝满足了市场多样化的需求。