Chemical Engineering and Applied Chemistry

Yield and productivity are critical for the economics and viability of a bioprocess. In metabolic engineering, the main objective is the increase of a target metabolite production through genetic engineering. However, genetic manipulations usually result in lower productivity due to growth impairment.

Recent advances in synthetic biology have equipped 9 us with new tools for bioprocess optimization at the genetic level. 10 Previously, we have presented an integrated in silico design for the 11 dynamic control of gene expression based on a density-sensing unit 12 and a genetic toggle switch. In the present paper, analysis of a serine- 13 producing Escherichia coli mutant shows that an instantaneous OFF switch leads to a maximum theoretical productivity improve-15 ment of 29.6% compared to the mutant. To further the design, 16 global sensitivity analysis is applied here to a mathematical model of 17 serine production in E. coli coupled with a genetic circuit. The model 18 of the quorum sensing and the toggle switch involves 13 parameters of which 3 are identified as having a significant effect on 19 serine concentration. Simulations conducted in this reduced parameter space further identified the optimal ranges for these 3 key 20 parameters to achieve productivity values close to the maximum theoretical values. This analysis can now be used to guide the 21 experimental implementation of a dynamic metabolic engineering strategy and reduce the time required to design the genetic 22 circuit components.

Synthetic biology, which involves the design of genetic circuits, has been valuable for understanding and engineering biological systems. Such genetic circuits could be valuable in metabolic engineering applications, where the goal is to manipulate the machinery of the organism in order to force or improve the bioengineering objective (which is typically in conflict with the organism's objective governed by evolution, i.e. to optimally allocate the resources for growth).

A microencapsulation-based technology platform has been developed for salt double fortification with iron and iodine, aiming to address two globally prevalent micronutrient deficiencies simultaneously. Specifically, ferrous fumarate was microencapsulated into a form of salt grain-sized premix, and then added into iodised salt. The earlier process involved fluidised-bed agglomeration followed by lipid coating. To improve physico-chemical properties of the iron premix, the use of cold-forming extrusion for agglomerating and microencapsulating ferrous fumarate was investigated and optimized in this study, leading to optimal formulations and operation parameters. Grain flours were suitable for forming an extrudable dough incorporating high percentages of ferrous fumarate. All extruded iron particles, regardless of binders used, were rich in iron and had excellent iron in vitro digestibility. The extruded iron particles formed the basis of the final, microencapsulated iron premixes with desired particle size (300-700 mm), and other physical, chemical, nutritional, and organoleptic properties suitable for salt fortification.

The addition of folic acid to Double Fortified Salt (with iron and iodine) aims to simultaneously ameliorate three major micronutrient deficiencies in vulnerable populations. To make Triple Fortified Salt, we added folic acid to the iodine solution (first method) and the iron premix (second method) that are used to fortify salt with iron and iodine. When added through the solution, sodium carbonate was needed to dissolve folic acid and to adjust pH. Alternately, folic acid was added either to the iron core or sandwiched between the core and TiO2 layer of the iron premix. Folic acid and iodine were stable in all cases, retaining more than 70% of the added micronutrients after six months at 45 °C/60–70% relative hu. Adding folic acid to the premix's iron core is preferred as folic acid retention was slightly higher, and the added folic acid did not impact the salt's colour. The additional cost for adding the micronutrients to salt is about 27¢/person per year. Folic acid in th...

The stability of table salt double-fortified with iron as ferrous fumarate, and with iodine as potassium iodide or potassium iodate, has been investigated under actual field conditions of storage and distribution in the coastal and highland regions of Kenya. Seven 200-g sample packets of double-fortified salt in sealed polyethylene bags and a similar packet containing a datalogger for monitoring temperature and humidity were packaged with 21 sample bags of salt from another study into a bundle, which then entered the distribution network from a salt manufacturer's facility to the consumer. Iodine retention values of up to 90% or more were obtained during the three-month study. Double-fortified salt was prepared using ferrous fumarate microencapsulated with a combination of binders and coloring agents and coated with soy stearine, in combination with either iodated salt or salt iodized with potassium iodide microencapsulated with dextrin and coated with soy stearine. Most of the ...

A membrane-based protein isolation process was originally developed to produce nvo protein isolates €rom defatted canola meal. Both products had high protein content while low in phytates and essentially free of glucosinolates, thus representing a potential source of food-grade protein. As phenolic compounds present in canola bind to the proteins, and cause the dark colour and undesirable taste of these protein products or their aqueous solutions, the interactions between phenolic compounds aqd canola prateins were investigated using a series of chemical treatments in combination with membrane processing to break phenolicprotein complexes and separate the phenolics from the proteins. Approximately 50% of the phenolic compounds extractable in aqueous media was thus identified to be bound to canola protein by different mechanisms: ionic bonding, hydrophobic interactions, hydrogen bonding, and covalent bonding. Based on the study of phenolic-protein interactions, a variety of treatrnents was tested for the removal of phenolic compounds from canola protein. The combined use of these treatments was able to reduce the phenolic contents in the products by 80-90%. The original protein isolation process was then modified with the treatrnents to remove phenolics. The modified process produced two high-quality canola protein isolates, both of high protein content (>85%), low in phenolic acids (-200 mg/100 g), and essentially free of tannins, and the removal of phenoIic compounds improved the colour and taste of canola protein isolates. Also, as a necessary tool in this study, a new analytical method was developed for the detemination of total phenolic acid content in canola protein products, yiving accurate quantification in a reasonable time. My thesis supervisor, Professor L. L. Diosady deserves my utmost gratitude for it would have been impossible for me to carry out this prograrn without his guidance, support, encouragement, and above all, his faith in my capability of pursuing a Ph.D. degree. To me he has been and will always be a great mentor. 1 am also very grateful to the other two members of my reading cornmittee, Professors M. J. Phillips and D. G. B. Boocock, who gave much valuable advise and many constructive suggestions throughout the prograrn. Al1 the members on my oral defense cornmittee have obliged me with their important input to my thesis, among whom are Professor M. Naczk from St.

Ferrous fumarate is useful in iron fortification because of its high bioavailability, mild taste, and relatively low cost. A ferrous fumarate premix for incorporation into salt has been developed by agglomerating ferrous fumarate with appropriate binder materials into salt-size particles followed by microencapsulation. The bioavailability of iron is critical for the usefulness of double-fortified salt. This study examined the in vitro bioavailability of various iron forms in double-fortified salt and microencapsulated ferrous fumarate premixes prepared by various techniques in an effort to identify key processing factors affecting iron bioavailability. Iron in vitro bioavailability was approximated through the rate of dissolution of iron in 0.1 N HCl, which closely approximates the acid in gastric juice. Iron in vivo bioavailability was tested using the hemoglobin repletion assay in rats. The materials and techniques used in microencapsulating ferrous fumarate had little effect on i...

Ultra Rice grains are micronutrient-fortified, extruded rice grains designed to address specific nutritional deficiencies in populations where rice is a staple food. Vitamin A and some of the B vitamins, as well as iron and zinc, are target nutrients for fortification through Ultra Rice technology. Vitamin A is sensitive to degradation. Therefore, the original Ultra Rice formulations included stabilizers, some of which were not approved as food additives in all of the receiving markets. To develop a new antioxidant system for improving vitamin A storage stability in Ultra Rice grains, while complying with international food regulations. Ten formulations were prepared containing various combinations of hydrophilic and hydrophobic antioxidants, as well as moisture stabilizers. Accelerated vitamin A storage stability tests were conducted at 25 degrees, 35 degrees, and 45 degrees C with 70% to 100% relative humidity. The most stable samples contained one or more phenolic antioxidants, a...

Dietary micronutrient deficiencies, which lead to diseases such as iodine deficiency disorders, iron-deficiency anemia, and vitamin A deficiency, are serious public health problems in the developing world. Fortifying salt with iodine, iron, and vitamin A is an attractive approach to simultaneously reduce the deficiencies of these three micronutrients in the diet. To explore the technical feasibility of producing triple-fortified salt fortified with iodine, iron, and vitamin A that would be stable under the climatic conditions of developing countries (i.e., high temperature and high humidity). Triple-fortified salt was obtained by granulation and encapsulation of commercially produced vitamin A products, iodine, and iron compounds. Vitamin A retention was determined in the presence of five iron and two iodine compounds, in different combinations, under three different storage conditions. The influence of commercial stabilization techniques for the vitamin A palmitate source used (spr...

Deficiencies in small quantities of micronutrients, especially iodine and iron, severely affect more than a third of the world's population, resulting in serious public health consequences, especially for women and young children. Salt is an ideal carrier of micronutrients. the double fortification of salt with both iodine and iron is an attractive approach to the reduction of both anemia and iodine-deficiency disorders. Because iodine is unstable under the storage conditions found during the manufacturing, distribution, and sale of salt in most developing countries, the effects of packaging materials and environmental conditions on the stability of salt double-fortified with iron and iodine were investigated. Salt was double-fortified with potassium iodide or potassium iodate and with ferrous sulfate or ferrous fumarate. the effects of stabilizers on the stability of iodine and iron were followed by storing the salt under three conditions that represent the extremes of normal d...

Commercially available field test kits for the determination of iodate in salt were tested to evaluate their performance and to devise improvements in their range and accuracy. Dropper tests based on the blue colour of the starch-iodine complex formed with iodine released by excess potassium iodide gave rapid qualitative indication of the presence of iodate. Because of the dark colour of the complex, the tests were found to be quantitative over only a limited range, typically 0 to 20 μg of iodine per gram of salt. We have developed methods for improving the reliability and colour reproducibility of these types of kits. Instructions for producing reliable kits of this type with improved colour reproducibility are presented. Improved qualitative tests in the range of 0 to 50 μg/g were obtained with a simple liquid-phase colourimetric system, based on the same chemistry. A field test kit was developed and tested in laboratories in India and Zimbabwe, as well as in our laboratory in Tor...

Double fortified salt containing both potassium iodate and ferrous fumarate microcapsules was produced at an Indian commercial facility. The packaged product became discolored, turning yellow, to a degree that would impact consumer acceptance. Therefore, there was a need for an investigation into the cause and possible remedy for this discoloration. The components of the fortified salt product, storage conditions, and processing characteristics were taken into consideration. Canadian and Indian salt samples were prepared unfortified as well as with iodine and/or iron microcapsules; stored at 25˚C and 45˚C in glass, polyethylene, or commercial polymer film. Some samples were heat treated prior to storage. Salt samples containing iodine that were heated before storage in packaging material turned yellow in color. From this study, it was found that due to heat and the presence of a sacrificial antioxidant component in the packaging film, potassium iodate was reduced to elemental iodine (I 2 ) turning packaged salt samples to a yellow/orange color. Hence it is recommended that in the manufacture of foods containing potassium iodate, the packaging material selected should be free from readily accessible antioxidants.

Salt iodization is widely available throughout the developing world. Incorporating other micronutrients into the existing salt iodization process could prevent multiple deficiencies. The thesis objective was to develop a stable formulation of salt dual fortified with folic acid and iodine, using a single solution that could be sprayed on. The micronutrients needed to be fully solubilized and stable in solution for at least one month. In the absence of an alkaline environment or antioxidant, iodine losses occur most likely due to the oxidation of folic acid by potassium iodate. Optimal salt formulations were prepared by spraying a pH 9 carbonate-bicarbonate buffer solution containing folic acid and iodine dissolved at 0.35% (w/v) each. Acceptable micronutrient retentions of > 90% were observed in refined salt after 6 months of storage at 45°C/60% relative humidity. Further investigations into increasing the concentration of iodine and folic acid in the spray solution are recommended.