Enhancement of the fermentation process and properties of bacterial cellulose: a review

Cellulose produced by bacteria (BC) has attracted increasing interest in view of its superior properties with respect to nanofibrillar structure, high purity and biocompatibility. Despite the intensive research, industrial production of BC has been limited, due to the low productivity, and the high cost of raw materials. This paper reviews the new approaches tried recently to get BC production feasible at large scale as the reduction in the quality of raw materials, the use of by-products and the optimization of the culture method. In addition, the new trends of enhancing specific properties of BC by varying culture conditions or by using additives have been reviewed. Thus, the paper presents how to obtain and enhance a desired property of BC for a specific use. This new approach will help researchers to develop new ideas in this field which will favour the commercialization of products made with BC and their industrial application.     

Application of novel technology to the abe fermentation process

Applied Biochemistry and Biotechnology - Traditional technology for ABE production and recovery does not allow an economic process. However, use of a fluidized-bed reactor using immobilized cells...     

The analysis of process gases: a review

 A general review of key issues involved in the analysis of process gases is presented. The reasons for such measurements – which include safety, quality, environmental and economic factors are considered. The technical issues arising from these measurements are dependent upon a variety of factors, including the overall sampling system, the type of analytical instrumentation, methods of data collection and the specified calibration protocols. The use of gas calibration cylinders as transfer standards is detailed and issues of stability and traceability to reference material discussed. Received: 1 March 2000 / Accepted: 31 March 2000     

Development of continuous fermentation using immobilized yeast cells for wine cooler process development

The continuous wine fermentation process, which employs a newly designed tapered column type bioreactor and immobilized yeast cells (Montrachet 522), was studied and its fermentation performance was compared with batch and suspended cell continuous wine fermentation systems. It was found that a stable continuous culture fermentation process could be maintained for a period of 2–3 mo when the new bioreactor system packed with immobilized yeast cells was employed. The new bioreactor containing immobilized yeast cells performed significantly better than the suspended cell culture system or batch culture. The effluent wine from the continuous fermentor system contained 7.1% (v/v) ethanol and 0.18% (w/v) residual sugar at 0.01 h^-1 dilution rate. The new continuous bioreactor system also gave 17–34 times higher maximum ethanol productivity compared to the conventional batch wine fermentation. At a low dilution rate, 0.01^-1, as high as 92% sugar to ethanol yield was achieved. Based on the results obtained from this study, the possibility of developing a continuous wine cooler fermentation process was demonstrated. A two-stage continuous wine fermentation system may be designed and operated. The grape juice can be fed into the first-stage that is operated at about 0.2 h^-1 dilution rate and the effluent from the first-stage is fed into the second-stage continuous fermentor operated at about 0.01 h^-1 dilution rate. By doing so, a wine cooler can be produced continuously and efficiently, by employing the newly designed tapered column type bioreactor charged with the immobilized yeast cells.     

Pervaporation-based hybrid process: a review of process design,applications and economics

Pervaporation is one of the developing membrane technologies that can be used for various industrial applications but for a predefined task, the optimal process design is unlikely to consist solely of pervaporation. Often the optimised solution becomes a hybrid process combining pervaporation with one or more other separation technologies. A distinction will be made between hybrid and integrated processes. Hybrid processes are important and consequently need to be considered in process design. This paper focuses on pervaporation–based hybrid processes that have been realised on an industrial scale. Both present and future prospects of applying these process combinations will be reviewed. The emphasis of this paper is, therefore, on pervaporation combined with distillation and with chemical reactors. The economic potential of these hybrid processes is evaluated, for various applications, by cost comparisons between the pervaporation-based hybrid processes and alternative separation processes. Pervaporation-based processes for waste water treatment and biotechnology applications involve other types of pervaporation based hybrid processes and have been excluded from this review.     

The surface chemistry of Bayer process solids: a review

The Bayer process is used for refining bauxite to smelting grade alumina (Al₂O₃), the precursor to aluminium. The process was developed and patented by Karl Josef Bayer 110 years ago, and has become the cornerstone of the aluminium production industry worldwide. Production of alumina reached 46.8 megatonnes (Mt) worldwide by the end of 1997, with Australia the worlds largest producer of bauxite and refiner of alumina with just under 30% of world production. Although the refining process is well established and the basic theories underpinning it are well defined, the fundamental chemistry of the Bayer process is not well understood. Of particular interest to industrial and academic researchers alike, is the chemistry of the Bayer process solids—aluminium trihydroxide, ‘red mud’ and sodium oxalate. The surface chemistry of these solids is of great industrial importance as the refining industry experiences significant restrictions due to limitations imposed on the process by surface chemical reactions. Of scientific interest is the conceptual advancement of our knowledge and understanding of the nature of surfaces under extreme (non-ideal) conditions. A review of the current literature relating to these important Bayer process solids is thus presented. While not exhaustive, the review is thorough and aims to familiarise the reader with current levels of understanding regarding the nature of Bayer process solids surfaces under Bayer process conditions, and the significant roles these solids play in the overall efficiency of the refining process. It is hoped that this review will provide a useful starting point for researchers new to the area of Bayer process research, whilst also stimulating further fundamental research in this economically and scientifically significant area.     

Estimation of temperature dependent parameters of a batch alcoholic fermentation process

In this work, a procedure was established to develop a mathematical model considering the effect of temperature on reaction kinetics. Experiments were performed in batch mode in temperatures from 30 to 38 degrees C. The microorganism used was Saccharomyces cerevisiae and the culture media, sugarcane molasses. The objective is to assess the difficulty in updating the kinetic parameters when there are changes in fermentation conditions. We conclude that, although the re-estimation is a time-consuming task, it is possible to accurately describe the process when there are changes in raw material composition if a re-estimation of parameters is performed.     

Continuous alcoholic fermentation process in a tower reactor with recycling of flocculating yeast

The influence of different substrate concentrations on the performance of a continuous system of alcohol prduction by fermentation using a tower reactor with recycling of flocculating yeasts was investigated. All experiments were carried out using a flocculating yeast strain IR-2, isolated from fermented food, and identified asSaccharomyces cerevisiae. Cane sugar juice was used as a substrate with sugar concentrations of 160, 170, 180, 190, and 200 g/L. Constant values of dilution rate, 0.20 h^?1, temperature, 30°C, and pH 3.3, were used. The performance of the reactor was observed to be efficient with high substrate concentrations. Maximum productivities of 18 g/L/h, 99% substrate conversion and ethanol concentrations of 90 g/L were obtained using 200 g/L of sugar in the feedstock. For substrate concentrations of 160 g/L, a maximum yield of 0.45 g of ethanol/g of sugar was observed or 90% of the theoretical value.

     

Application of microbiological sensors in fermentation processes

A review is presented of microbiological sensors which are composed of micro-organisms immobilized in a membrane and coupled to a sensing element. Conventional microbiological sensors such as those for biochemical oxygen demand (BOD), ethanol and acetic acid are discussed briefly. Novel sensors are then described. The sensor for carbon dioxide is based on a chemoautotrophic bacterium, that for alcohol on cell membranes of the acetic acid bacteria, Gluoconabacter suboxydans. Sensors for BOD carbon dioxide are based on thermophilic bacteria. Finally, a microbial field effect transistor sensor (FET) for alcohol sensor is described. For all the sensors, the ranges of linear response and their long-term stabilities are reported.     

Use ofK L a as a criterion for scaling up the inulinase fermentation process

Applied Biochemistry and Biotechnology - The scale-up of inulinase production in aerated cultures ofCandida kefyr DSM 70106 was studied, taking into account the criterion of maintainingK L a...     

Discrimination between ethanol inhibition models in a continuous alcoholic fermentation process using flocculating yeast

Discrimination between different rival models for describing the inhibitory effect of ethanol both on yeast growth and on fermentation was studied for a continuous process of alcoholic fermentation in a tower reactor with recycling of flocculating cells. Models tested include linear, parabolic, hyperbolic, exponential, and generalized nonlinear power-law types. The best expressions were identified under the criteria that all the kinetic parameters should assume acceptable values in a feasible range and should result in the best fit of the experimental data. The kinetic parameters were estimated from steady-state data of several sugar concentrations in feeding stream (S₀ = 160, 170, 180, 190, 200 g/L), constant dilution rate (D = 0.2 h^-1), recycle ratio (α = 13.6), and temperature (T = 30°C). The best model for the yeast growth was of power-law type, whereas for the product formation the best model was of linear type. These models were able to reproduce the trends of the process variables satisfactorily.     

Partitioned partial least squares regression with application to a batch fermentation process

The performance of Partial Least Squares regression (PLS) in predicting the output with multivariate cross‐ and autocorrelated data is studied. With many correlated predictors of varying importance PLS does not always predict well and we propose a modified algorithm, Partitioned Partial Least Squares (PPLS). In PPLS the predictors are partitioned into smaller subgroups and the important subgroups with high prediction power are identified. Finally, regular PLS analysis using only those subgroups is performed. The proposed Partitioned PLS (PPLS) algorithm is used in the analysis of data from a real pharmaceutical batch fermentation process for which the process variables follow certain profiles during a specific fermentation period. We observed that PPLS leads to a more accurate prediction of the yield of the fermentation process and an easier interpretation, since fewer predictors are used in the final PLS prediction. In the application important issues such as alignment of the profiles from one batch to another and standardization of the predictors are also addressed. For instance, in PPLS noise magnification due to standardization does not seem to create problems as it might in regular PLS. Finally, PPLS is compared to several recently proposed functional PLS and PCR methods and a genetic algorithm for variable selection. More specifically for a couple of publicly available data sets with near infrared spectra it is shown that overall PPLS has lower cross‐validated error than PLS, PCR and the functional modifications hereof, and is similar in performance to a more complex genetic algorithm. Copyright © 2011 John Wiley & Sons, Ltd.     

Recent development in HPLC enantioseparation — a selected review

Summary Recent developments in the field of separating optical isomers by HPLC are discussed in this brief review. In particular it is focussed on various techniques for direct enantioseparation, the interpretation of possible enantioselective separation mechanisms, and the advantages and limitations of the diverse methods. This goal is supported by representative and selected examples of chiral separations.     

In situ monitoring of the seed stage of a fermentation process using non-invasive NIR spectrometry

Non-invasive NIR spectrometry has been used to monitor in situ the seed stage of a streptomyces fermentation process. The main spectral change occurred at 7263 cm(-1) in the 1st derivative spectrum, and from comparison with off-line NIR spectra acquired of components present in the fermentation broth, can be attributed to biomass. The biomass signal was constant for the first 20 h of the seed stage, after which it decreased before increasing again. The time at which the minimum occurred in the NIR profile was either the same or slightly earlier than that at which a maximum in the carbon dioxide evolution rate (CER) occurred. The changes observed for the biomass signal in the NIR spectra can be attributed to growth and then fragmentation of mycelia, which indicates a change in metabolic activity. Hence, it may be possible to use NIR spectrometry in situ to determine the optimum transfer time for the seed stage of a fermentation process. Spectra were also acquired of the final stage of the same fermentation process. The variation in the biomass signal in the NIR spectra was more complicated in the final stage owing to changes in stir rate, and biomass concentration and morphology.     

The process of management review

Management review of the quality-management system is an item in many quality standards and a requirement of the ISO 9001:2000 standard and of laboratory standards ISO 15189 and ISO 17125, and others. These reviews are conducted to ensure that the top management is informed and involved in the quality-management system with respect to continuing adequacy and effectiveness, and opportunities for improvement of the system. The management review is a process that should be conducted and audited utilizing the process approach. A process approach is defined as “An activity using resources and managed in order to enable the transformation of inputs into outputs” (ISO 9001:2000). All identified main processes in the quality system should be monitored through data collection by appropriate methods, assuring that data are valid, representative, and adequate. For management review data must be collected and presented in an accessible form so that processes can be evaluated according to objectives, goals, resources, etc. On the basis of this information the laboratory management makes the necessary decisions and ensure that actions are taken that improve the effectiveness of the quality-management system. As output from the management review process, there should be evidence of decisions regarding: change of quality policy and objectives; plans and possible actions for improvements; corrective actions as appropriate; increased customer satisfaction; and planning of resources needs. Identification of the processes involved and using the process approach in the management review ensures the continual improvement of the quality system. Presented at the conference Quality in the Spotlight, March 2006, Antwerp, Belgium.     

Evaluation of optimization techniques for an extractive alcoholic fermentation process

The mathematical optimization of a continuous alcoholic fermentation process combined with a flash column under vacuum was studied. The objective was to maximize % yield and productivity in the fermentor. The results using surface response analysis combined with modeling and simulation were compared withy those obtained when the problem was written as a nonlinear programming problem and was solved with a successive quadratic programming (SQP) technique. Two process models were evaluated when the process was optimized using the SQP technique. The first one is a deterministic model, whose kinetic parameters were experimentally determined as functions of the temperature, and the second is a statistical model obtained using the factorial design technique combined with simulation. Although the best result was the one obtained using the rigorous model, the values for productivity and % yield obtained using the simplified model are acceptable, and these models can be used when the development of a rigorous model is excessively difficult, slow, or expensive.     

Optical interrogation of molecularly imprinted polymers and development of MIP sensors: a review

This article reviews the progress and developments achieved in the past five years (2000–2005) in the application of optical analytical techniques to the evaluation of molecularly imprinted polymer (MIP) characteristics. The MIP binding efficiency, recognition processes and selectivity have been intensively studied by optical means due to the general high sensitivity and simplicity of the utilisation of optical techniques. In addition, recent progress in the covalent linkage of MIPs to optical transducers has allowed for the realisation of highly efficient and robust optical MIP-based molecular recognition sensors. The review provides insight into the various approaches to the optical interrogation of MIPs, and is organised according to the type of optical technique employed (fluorescence, UV/Vis and infrared spectroscopy, surface plasmon resonance, chemiluminescence, refractive interference spectroscopy and Raman scattering) and the detailed strategies applied. The review also covers the recent progress achieved in the area of optical sensors based on MIPs.     

The development of heat flow calorimetry as a tool for process optimization and process safety

Classical thermo-analytical micro methods (DTA, DSC) are still very useful for process work, but medium scale instruments based on heat flow measurement are attaining an increasingly important role in this domain. As in many areas, development of reaction calorimetry for industrial applications was driven by needs and by available means (technical capabilities). The needs have been fairly constant over the past decades. There are data needs:

Reaction rates

Heat release rates

Heat of desired reactions and decompositions

Heat capacities and heat transfer capacities

It took the specialists of calorimetry a long time to recognize and to accept the operational needs, namely:

Working under controlled temperature conditions (constant temperature, temperature ramps)

Adding components during runs (continuously or in portions)

Simulation of industrial mixing conditions

The main driving force for the development of process oriented calorimetric instruments was the evolution of electronic hardware which made the control of heat flow on a (non micro) laboratory scale easy. The paper gives an overview on the principles of heat flow control and reviews the developments of the fifties and sixties, when the matching of heat flow with heat release by reactions was the goal. With the advent of fast and powerful laptop computers, the focus has shifted. Now, the deduction of true heat release rates from signals which may be badly distorted, is the goal. Some recent developments are reviewed and the hope is expressed that calorimetric equipment, inexpensive enough to be affordable for every laboratory engaged in process work, will be available soon.     

Application of enriched stable isotopes as tracers in biological systems: a critical review

The application of enriched stable isotopes of minerals and trace elements as tracers in biological systems is a rapidly growing research field that benefits from the many new developments in inorganic mass spectrometric instrumentation, primarily within inductively coupled plasma mass spectrometry (ICP-MS) instrumentation, such as reaction/collision cell ICP-MS and multicollector ICP-MS with improved isotope ratio measurement and interference removal capabilities. Adaptation and refinement of radioisotope tracer experiment methodologies for enriched stable isotope experiments, and the development of new methodologies coupled with more advanced compartmental and mathematical models for the distribution of elements in living organisms has enabled a broader use of enriched stable isotope experiments in the biological sciences. This review discusses the current and future uses of enriched stable isotope experiments in biological systems.     

The telomerisation of 1,3-butadiene and carbon dioxide: process development and optimisation in a continuous miniplant

The telomerisation of 1,3-butadiene and carbon dioxide is one of the first homogeneously catalyzed reactions using carbon dioxide as a C1-building block. In this article we describe the process development for a miniplant applying this telomerisation in a continuous scale. Through repeated optimisation of the plant setup combined with parallel laboratory batch experiments the overall space-time-yield of the plant was enhanced significantly.