Processes2014, 2(3), 675-693; doi:10.3390/pr2030675 - published 18 August 2014 Show/Hide Abstract
Abstract: The synthesis of water networks based on properties has commonly ignored the effect of temperature on the property balances that are part of the formulation. When wide differences of temperatures are observed within the process, such an effect might yield significant errors in the application of conventional property balances. In this work, a framework for the development of water networks that include temperature effects on property balances is presented. The approach is based on the inclusion of constants in the property operators that are commonly used to carry out the property balances. An additional term to take care of composition effects is also included. The resulting approach is embedded into a formulation based on a mixed-integer nonlinear programming model for the design of water networks. A case study is presented that shows that the proposed approach yields an improvement in the prediction of the resulting properties for the integrated network, thus affecting the optimal solution.
Processes2014, 2(3), 658-674; doi:10.3390/pr2030658 - published 13 August 2014 Show/Hide Abstract
Abstract: The objective of this study was to characterize our designed through-thickness perfusion bioreactor which could generate large scaffold-free tissue engineered cartilage constructs. The hypothesis being that through-thickness perfusion could accelerate maturation of scaffold-free tissue engineered cartilage, grown in transwell culture inserts large enough to repair typical size chondral lesions in the human knee. Internal cell culture media temperature and pH were examined over time, upon implementation of the bioreactor perfusion system inside a CO2 incubator, to ensure adequate regulation conducive to cell viability. Results indicate that temperature and pH both equilibrate within approximately 3 h. The bioreactor was tested for its efficacy to support formation of 4.5 cm2 constructs by porcine neonatal chondrocytes. Tests were conducted under three conditions: immediate perfusion with flow from bottom to top, immediate perfusion with media flow from top to bottom, and bottom to top perfusion after four weeks of static culture, giving the cells time to self-aggregate into a consolidated construct prior to perfusion. The best cell culture results were obtained when perfusion was delayed for four weeks relative to the immediate perfusion of the other methods, and this should be further investigated.
Processes2014, 2(3), 639-657; doi:10.3390/pr2030639 - published 8 August 2014 Show/Hide Abstract
Abstract: The use of multifactorial design of experiments (DoE) in tissue engineering bioprocess development will contribute to the robust manufacturing of tissue engineered constructs by linking their quality characteristics to bioprocess operating parameters. In this work, perfusion bioreactors were used for the in vitro culture and osteogenic differentiation of human periosteum-derived cells (hPDCs) seeded on three-dimensional titanium (Ti) alloy scaffolds. A CaP-supplemented medium was used to induce differentiation of the cultured hPDCs. A two-level, three-factor fractional factorial design was employed to evaluate a range of bioreactor operating conditions by changing the levels of the following parameters: flow rate (0.5–2 mL/min), cell culture duration (7–21 days) and cell seeding density (1.5 × 103–3 × 103 cells/cm2). This approach allowed for evaluating the individual impact of the aforementioned process parameters upon a range of genes that are related to the osteogenic lineage, such as collagen type I, alkaline phosphatase, osterix, osteopontin and osteocalcin. Furthermore, by overlaying gene-specific response surfaces, an integrated operating process space was highlighted within which predetermined values of the six genes of interest (i.e., gene signature) could be minimally met over the course of the bioreactor culture time.
Processes2014, 2(3), 625-638; doi:10.3390/pr2030625 - published 7 August 2014 Show/Hide Abstract
Abstract: The eukaryotic green alga, Chlamydomonas reinhardtii, is a unique expression platform that can efficiently express complex therapeutic proteins. However, demonstrating that therapeutic molecules can be produced in quantifiable levels is essential to establish the potential of the C. reinhardtii expression system. Thus, the objective of this investigation was to determine the process conditions that could maximize C. reinhardtii biomass accumulation and induced-production of the two recombinant proteins, a single chain fragment antibody molecule (αCD22 scFv) and malaria vaccine antigen (Pfs25), produced in the chloroplast of C. reinhardtii.To achieve a higher production of recombinant proteins, cultivation variables of C. reinhardtii, such as mixing, light-induction time and intensity, nutrient depletion and culture age, were investigated and optimized. The optimal light-induction time was 24 h at a light intensity of 300 μmol m−2 s−1. Replacement of the culture media in the late exponential growth with fresh media was beneficial to the accumulation of recombinant proteins. Optimization led to increases in the accumulation of recombinant proteins by six-fold and the recombinant protein fraction in the extracted soluble protein by two-fold.
Processes2014, 2(3), 596-624; doi:10.3390/pr2030596 - published 5 August 2014 Show/Hide Abstract
Abstract: Increasing epidemiological and experimental data now emphasize that a diet rich in vegetables and fruits confers many health benefits. Functional products containing elevated levels of bioactive compounds are attracting considerable attention due to their potential to lower the risk of chronic diseases and their associated huge healthcare costs. On a global scale, there is an increasing demand for berries and fruits, since they are natural polyphenol-rich raw material to be incorporated into functional foods, nutraceuticals and pharmaceuticals. This is a major challenge for both industry and horticultural experts, because the content of health-promoting compounds in plants varies widely not only in different plant species, but also between cultivars. The content is also significantly affected by harvesting, storage and processing factors. This review summarizes the recent data and clarifies the main contributors of harvesting time, various storage conditions and post-harvest procedures, such as temperature management, controlled atmosphere, 1-MCP, calcium and plant activators, as ways to influence health-promoting compounds in fruits. Furthermore, the ways processing factors, e.g., enzymatic treatment, pressing, clarification, temperature, pressure and fermentation, can influence the levels of polyphenols and vitamins in berries and soft fruits will be discussed. Finally, strategies for preventing the decline of health-promoting compounds in fruits during long-term storage will be assessed in light of recent scientific progress and modern methods, which preserve the levels of polyphenols, will be highlighted.
Processes2014, 2(3), 570-595; doi:10.3390/pr2030570 - published 4 August 2014 Show/Hide Abstract
Abstract: Broad evidence exists for cross talk between the Mitogen-activated protein kinases (MAPK) pathway and Smad-dependent TGF-β signal transduction. A variety of studies, oftentimes involving different cell types, have identified several potential mechanisms for the crosstalk. However, there is no clear consensus on the actual mechanism(s) responsible for the crosstalk. This work develops a model of the pathway, including several hypothesized crosstalk mechanisms, and discusses which of the potential mechanisms can appropriately describe observed behaviors. Simulation results show a good agreement of the findings with results reported in the literature.