Milena Fernandes da Silva

Lichtheimia blakesleeana as a new potencial producer of phytase and xylanase.

Brazil is known for its great potential for production of renewable resources such as agro-industrial residues. These residues can be used as alternative sources of new products. Meanwhile, solid-state fermentation, with its advantages of energy conservation and pollution reduction, has been identified as a process of great potential for the production of bioactive compounds, especially enzymes. In the present work, a 23 factorial design was used to evaluate the effects of pH, temperature and moisture on the production of phytase and xylanase by Lichtheimia blakesleeana URM 5604 through the fermentation of citrus pulp. Statistical analyses of the results showed that the only the pH influenced the production of these enzymes, with the best phytase production (264.68 U/g) ocurring at pH 6.0, 34 °C, initial moisture 50%, after 48 hours of culture. The best conditions for xylanase production (397.82 U/g) were fermentation for 120 hours at pH 4.0, 26 °C and initial moisture of 70%. The best parameters for the simultaneous production of phytase (226.92 U/g) and xylanase (215.59 U/g) were determined to be initial moisture of 50%, pH 6.0, 26 °C, and 48 hours of fermentation.

A new bioenergetic and thermodynamic approach to batch photoautotrophic growth of Arthrospira (Spirulina) platensis in different photobioreactors and under different light conditions.

Photobioreactor configuration, mode of operation and light intensity are known to strongly impact on cyanobacteria growth. To shed light on these issues, kinetic, bioenergetic and thermodynamic parameters of batch Arthrospira platensis cultures were estimated along the time at photosynthetic photon flux density (PPFD) of 70μmolm(-2)s(-1) in different photobioreactors with different surface/volume ratio (S/V), namely open pond (0.25cm(-1)), shaken flask (0.48cm(-1)), horizontal photobioreactor (HoP) (1.94cm(-1)) and helicoidal photobioreactor (HeP) (3.88cm(-1)). Maximum biomass concentration and productivity remarkably increased with S/V up to 1.94cm(-1). HoP was shown to be the best-performing system throughout the whole runs, while HeP behaved better only at the start. Runs carried out in HoP increasing PPFD from 40 to 100μmolm(-2)s(-1) revealed a progressive enhancement of bioenergetics and thermodynamics likely because of favorable light distribution. HoP appeared to be a promising configuration to perform high-yield indoor cyanobacterial cultures.

Chlorella vulgaris as a lipid source: Cultivation on air and seawater-simulating medium in a helicoidal photobioreactor

The freshwater microalga Chlorella vulgaris was cultured batchwise on the seawater‐simulating Schlösser medium either in a 1.1‐L‐working volume helicoidal photobioreactor (HeP) or Erlenmeyer flask (EF) as control and continuously supplying air as CO2 source. In these systems, maximum biomass concentration reached 1.65 ± 0.17 g L−1 and 1.25 ± 0.06 g L−1, and maximum cell productivity 197.6 ± 20.4 mg L−1 day−1 and 160.8 ± 12.2 mg L−1 day−1, respectively. Compared to the Bolds Basal medium, commonly employed to cultivate this microorganism on a bench‐scale, the Schlösser medium ensured significant increases in all the growth parameters, namely maximum cell concentration (268% in EF and 126% in HeP), maximum biomass productivity (554% in EF and 72% in HeP), average specific growth rate (67% in EF and 42% in HeP), and maximum specific growth rate (233% in EF and 22% in HeP). The lipid fraction of biomass collected at the end of runs was analyzed in terms of both lipid content and fatty acid profile. It was found that the seawater‐simulating medium, despite of a 56–63% reduction of the overall biomass lipid content compared to the Bolds Basal one, led in HeP to significant increases in both the glycerides‐to‐total lipid ratio and polyunsaturated fatty acid content compared to the other conditions taken as an average. These results as a whole suggest that the HeP configuration could be a successful alternative to the present means to cultivate C. vulgaris as a lipid source.

Doxycycline Degradation by the Oxidative Fenton Process

Doxycycline is a broad-spectrum tetracycline occurring in domestic, industrial, and rural effluents, whose main drawback is the increasing emergence of resistant bacteria. This antibiotic could be degraded by the so-called Fenton process, consisting in the oxidation of organic pollutants by oxygen peroxide (H2O2) in the presence of Fe2

Characterisation of bare and tannase-loaded calcium alginate beads by microscopic, thermogravimetric, FTIR and XRD analyses

Incorporating enzymes into calcium alginate beads is an effective method to immobilise them and to preserve, at the same time, their catalytic activity. Sodium alginate was mixed with Aspergillus ficuum tannase in aqueous solution, and tannase-loaded calcium alginate beads were prepared using a simple droplet-based microfluidic system. Extensive experimental analysis was carried out to characterise the samples. Microscopic imaging revealed morphological differences between the surfaces of bare alginate matrix and tannase-loaded alginate beads. Thermal analysis allowed assessing the hydration contents of alginate and revealed the presence of tannase entrapped in the loaded beads, which was confirmed by vibrational spectroscopy. X-ray diffraction allowed us to conclude that alginate of tannase-loaded beads is not crystalline, which would make them suitable as carriers for possible controlled release. Moreover, they could be used in food applications to improve tea quality or clarify juices.

Brazilian Kefir-Fermented Sheep’s Milk, a Source of Antimicrobial and Antioxidant Peptides

Fermented milks are a source of bioactive peptides and may be considered as functional foods. Among these, sheep’s milk fermented with kefir has not been widely studied and its most relevant properties need to be more thoroughly characterized. This research study is set out to investigate and evaluate the antioxidant and antimicrobial properties of peptides from fermented sheep’s milk in Brazil when produced by using kefir. For this, the chemical and microbiological composition of the sheep’s milk before and after the fermentation was evaluated. The changes in the fermented milk and the peptides extracted before the fermentation and in the fermented milk during its shelf life were verified. The antimicrobial and antioxidant activities of the peptides from the fermented milk were evaluated and identified according to the literature. The physicochemical properties and mineral profile of the fermented milk were like those of fresh milk. The peptide extract presented antimicrobial activity and it was detected that 13 of the 46 peptides were able to inhibit the growth of pathogenic microorganisms. A high antioxidant activity was observed in the peptides extracted from fermented milk (3.125 mg/mL) on the 28th day of storage. Two fractions displayed efficient radical scavenging properties by DPPH and ABTS methods. At least 11 peptides distributed in the different fractions were identified by tandem mass spectrometry. This sheep’s milk fermented by Brazilian kefir grains, which has antioxidant and antimicrobial activities and probiotic microorganisms, is a good candidate for further investigation as a source for bioactive peptides. The fermentation process was thus a means by which to produce potential bioactive peptides.

Immobilization of Aspergillus ficuum tannase in calcium alginate beads and its application in the treatment of boldo (Peumus boldus) tea

Tannase (tannin acyl hydrolase, E.C. 3.1.1.20) is an enzyme that catalyzes the hydrolysis of ester and depside linkages in hydrolysable tannins such as tannic acid, releasing gallic acid and glucose. It has several commercial applications in food industry, among which are gallic acid production, reduction of tannin content in fruit juices, and preparation of instantaneous tea. In this study we immobilized Aspergillus ficuum tannase in calcium alginate beads and then used it to treat boldo (Peumus boldus) tea. Such a technique allowed entrapping tannase with a 75% efficiency and appreciably increasing its thermal and pH stability compared with the free enzyme. Storage stability and reuse of the immobilized enzyme were very promising, in that about 60% of starting enzyme activity was retained after bead storage for 90 days at 4 °C or after six cycles of use. Boldo tea treatment with immobilized tannase for 120 min at 40 °C led to 31 and 60% removals of tannins and epigallocatechin gallate, an increase of about two orders of magnitude in gallic acid content, 56 and 109% increases in total flavonoids and epigallocatechin contents, a 42.8% increase in antioxidant activity and significant enhancements of tea color, clarity and pH.