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Submitted by Fátima Piedade (fpiedade@sa.isel.pt) on 2013-02-17T12:48:23Z No. of bitstreams: 1 Supercritical carbon dioxide extraction of bioactive compounds from microalgae and volatile oils fromaromatic plants.rep.pdf: 279813 bytes, checksum: 9bc79a5af01ddc7f004e86f79272064b (MD5) Made available in DSpace on 2013-02-17T12:48:23Z (GMT). No. of bitstreams: 1 Supercritical carbon dioxide extraction of bioactive compounds from microalgae and volatile oils fromaromatic plants.rep.pdf: 279813 bytes, checksum: 9bc79a5af01ddc7f004e86f79272064b (MD5) Previous issue date: 2011-12

The Laboratório Associado Institute for Biotechnology and Bioengineering (IBB) is a research unit aiming to be a strategic infrastructure for the development of the Portuguese R&D and innovation policies in the areas of Biotechnology, Bioengineering, Biomaterials and Life, Biomedical and Agricultural Sciences. IBB combines its R&D activities with advanced higher education, technology transfer, consulting and services, with the aim of fostering the industrial, health, agriculture and environmental sectors.

This paper discusses the importance of an engineering systems approach to international bioengineering education and how a new educationalresearch program, the MIT-Portugal Program Bioengineering Systems focus area, aims to develop future global bioengineering leaders. The program, comprising both post-graduate advanced studies and doctoral programs, commences in September 2007. Several other international-collaborative educational and research programs—such as the Cambridge-MIT Institute, the Singapore MIT Alliance, and the Socrates/Erasmus “Erasmus Programme”—offer lessons learned in international collaboration. The MPP Bioengineering Systems program differs from these programs in several respects. The unique collaboration in MPP offers an engineering systems approach, a joint degree offered by three Portuguese universities, and collaborative teaching and research efforts between MIT and Portuguese faculty and students.

The influence of sonication power, suspension volume and cell concentration on the kinetics of cytochrome b5 and intracellular protein release by sonication of Escherichia coli TB1 cells was studied. The influence of freezing and thawing of the cell suspension was also evaluated. Freezing and thawing increased the recovery yield of cytochrome b5. The sonication efficiency increased with the increase of sonication power and with the decrease of the suspension volume and cell concentration.

A commercial inulinase preparation from Aspergillus niger was immobilized into polyvinyl alcohol hydrogel lenticular particles (Lentikats®) and into hemispheric-shaped capsules, both based on the use of LentiKat® liquid. The characterization of the resulting biocatalysts, aiming at inulin hydrolysis to fructose, was performed, and the two methods of immobilization were compared. Temperature and pH profiles, as well as kinetic constants were determined, for both free and immobilized enzyme preparations. A broader-shaped curve was observed for the pH-activity profile when immobilized forms were compared to the free form. The apparent KM of inulinase increased roughly 2-fold upon immobilization in either form of the support particles, suggesting diffusion limitations of inulin inside the gel. Long-term operation with immobilized enzymes proved unfeasible above 55 °C, due to the lack of mechanical stability of the supports tested. When the temperature of incubation was lowered to 50 °C, the hemispheric form of the immobilized enzyme displayed considerable long-term operational stability, since it allowed 20 repeated, consecutive batch-mode runs, with a final decay in product yield of 20 %. When inulinase immobilized in Lentikats® particles was used, the final decay in product yield was roughly 70 %.

To significantly enhance the downstream processing, two cutinase variants were constructed by genetic fusion small hydrophobic peptides (WP)2 and (WP)4, respectively. However, the fusion of these peptides impairs cutinase secretion by the host cell Saccharomyces cerevisiae and increases cutinase inactivation in the culture broth due to cutinase aggregation, resulting in cutinase activities per biomass of 56 % of cutinase-(WP)2 and of 7 % of cutinase-(WP)4, in relation to cutinase without the hydrophobic tags. It was observed that the addition of non-ionic surfactant Tween-80 into the culture broth could minimise the cutinase inactivation. The addition of Tween-80 also results in the enhancement of cutinase secretion by the yeast cell, leading to 1.25 and 2.51 fold-higher extracellular cutinase-(WP)2 and cutinase-(WP)4, respectively, in relation to cultivations performed in the absence of surfactant. Therefore, the addition of Tween-80 on the culture broth partly minimises the effect of fusion of the hydrophobic tags on the inactivation of the enzymatic activity and on the reduction of the protein secretion. By this way, the use of Tween-80 on the S. cerevisiae cultivation may contribute to the efficiency enhancement of the downstream processing of tagged cutinases.

Fundação para a Ciência e a Tecnologia (FCT)