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Colorimetric Enzymatic Assay of L-Malic Acid Using Dehydrogenase from Baker’s Yeast

Maristela F.S. Peres1*, Cecilia Laluce2 and Edwil A.L. Gattás1


1
School of Pharmaceutical Science, São Paulo State University – UNESP, Department of Food and Nutrition, Rodovia Araraquara-Jaú, Km 1, BR-14801-902, SP, Brazil

2Department of Biochemistry and Chemical Technology, Institute of Chemistry, UNESP, R. Prof. Francisco Degni s/n C.P. 355, BR-14801-970, Araraquara, SP, Brazil

Article history:

Received July 17, 2006
Accepted September 23, 2007

Key words:

colorimetric assay of L-malic acid, fruit juices, wine, malate dehydrogenase (MDH), baker’s yeast

Summary:

A colorimetric method has been developed and optimized to measure L-malic acid in samples of fruit juices and wine. This method is based on oxidation of the analyte, catalyzed by malate dehydrogenase (MDH) from dry baker’s yeast, and in combination with the reduction of a tetrazolium salt (MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide). In the present study, the method exhibited sensitivity in the range of 500–4000 μM of L-malic acid in the reaction cuvette, with the lower detection limit of 6.7·10–2 g/L, the upper limit of 53.6·10–2 g/L and a maximum standard deviation of only 2.5 % for the analyzed samples. The MDH activity from baker’s yeast was also optimized, the enzyme showed a high stability at pH=8.0–9.0 and the activity was maintained completely at temperatures up to 40 °C for 1 hour. The results show that the colorimetric method using enzymatic preparations from dry baker’s yeast is a simple and low-cost method with possibility of wide application.

 


*Corresponding author:          fmrsperez@uol.com.br
                                               ++55 16 33 016 929
                                               ++55 16 33 016 920

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Production and Characterization of Poly(3-Hydroxybutyrate) from Oleic Acid by Ralstonia eutropha

Vitor Henrique Grigull1, Delne Domingos da Silva1, Michele Cristina Formolo Garcia1,2, Sandra Aparecida Furlan1, Ana Paula Testa Pezzin1, Andréa Lima dos Santos Schneider1* and Gláucia Falcão Aragão2


1Laboratory of Biotechnology, University of Joinville Region, Santa Catarina, BR-89201-972 Brazil

2Federal University of Santa Catarina, Florianópolis, BR-88800-000 Brazil

Article history:

Received August 23, 2006
Accepted June 25, 2007

Key words:

biopolymers, Ralstonia eutropha, oleic acid, characterization

Summary:

The aim of this research is to investigate the influence of oleic acid concentration on the cell growth and the physical properties of the polymer formed by cultures of Ralstonia eutropha in mineral medium. Cells were cultivated in Erlenmeyer flasks with 300 mL of mineral medium, containing glucose and fructose as a carbon source (30 g/L) and ammonium sulphate (5.0 g/L) as a nitrogen source. Oleic acid was added as nutritional supplement in different concentrations (0, 0.3, 0.9, 1.5 and 3.0 g/L) and the cells were incubated at 30 °C and 150 rpm. The films prepared by casting were evaluated by X-ray diffraction, thermogravimetry and differential scanning calorimetry. These results indicate that the increase of oleic acid concentrations leads to a higher specific growth rate and cell productivity. The characterization of the films revealed that the increase of the concentration of oleic acid from 0 to 1.5 g/L has no influence on thermal behaviour and crystallinity degree. However, the thermal stability, melting temperature, glass transition temperatures and crystallinity degree decreased when 3.0 g/L of oleic acid were used.



*Corresponding author:           aschneider@univille.br
                                               ++(55) 47 34 619 107
                                               ++(55) 47 34 619 077

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Production of Antioxidant Nutraceuticals by Solid-State Cultures of Pomegranate (Punica granatum) Peel and Creosote Bush (Larrea tridentata) Leaves

Cristóbal Noé Aguilar1*, Antonio Aguilera-Carbo2, Armando Robledo1, Janeth Ventura1, Ruth Belmares1, Diego Martinez1, Raul Rodríguez-Herrera1 and Juan Contreras1


1
Food Research Department, School of Chemistry, Universidad Autónoma de Coahuila, Saltillo, MX-25000 Coahuila, México

2Department of Food Science and Nutrition, Universidad Autónoma Agraria 'Antonio Narro', MX-25000 Buenavista, Saltillo, Coahuila, México

Article history:

Received August 8, 2006
Accepted January 5, 2007

Key words:

pomegranate peel, creosote bush, antioxidants, solid-state fermentation

Summary:

In this work, creosote bush (Larrea tridentata) leaves and pomegranate (Punica granatum) peels were characterized for their use as a source of antioxidants and a support in solid- state fermentation. This work focuses on the kinetic evaluation of physicochemical changes during the fungal fermentation of two tannin-rich plant materials, mainly on the polyphenolic content. Aspergillus niger GH1 was used in the fermentation processes, the cultures were monitored for 96 h. The content of proteins, crude fibres, lipids, reducing and total sugars was evaluated following the AOAC methods. Tannins were analyzed using a spectrophometric method. Biodegradation of ellagitannins was monitored kinetically and the accumulation of gallic and ellagic acids was determined by HPLC. Results demonstrated that pomegranate peel and creosote bush leaves are excellent supports for solid-state fermentation and sources of antioxidants.

 


*Corresponding author:           cag13761@mail.uadec.mx
                                               ++52 844 4159 534

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Fungal Biodegradation of Tannins from Creosote Bush (Larrea tridentata) and Tar Bush (Fluorensia cernua) for Gallic and Ellagic Acid Production

Janeth Ventura1, Ruth Belmares1, Antonio Aguilera-Carbo2, Gerardo Gutiérrez-Sanchez3, Raul Rodríguez-Herrera1 and Cristóbal Noé Aguilar1*


1
Food Research Department, School of Chemistry, Universidad Autónoma de Coahuila, Saltillo, MX-25 000 Coahuila, Mexico

2Department of Food Science and Nutrition, Universidad Autónoma Agraria 'Antonio Narro', Buenavista, Saltillo, MX-25 000 Coahuila, Mexico
3Complex Carbohydrate Research Center, The University of Georgia, 315 Riverband Road, GA-30602-4712 Athens, USA

Article history:

Received July 11, 2006A
Accepted June 13, 2007

Key words:

Aspergillus niger PSH, creosote bush, tar bush, gallic acid, ellagic acid

Summary:

In the present work, the production of two potent antioxidants, gallic and ellagic acids, has been studied using solid-state fermentation (SSF) of tannin-rich aqueous plant extracts impregnated in polyurethane foam. Extracts from creosote and tar bush were inoculated with Aspergillus niger PSH spores and impregnated in the polyurethane support. The kinetics of the fermentation was monitored every 24 h. The maximum biodegradation of hydrolysable and condensed tannins was, respectively, 16 and 42 % in creosote bush, and 40 and 83 % in tar bush. The maximal productions of gallic and ellagic acid (152 and 177 %, respectively) were reached with aqueous extracts of creosote bush. Tar bush extracts inoculated with A. niger PSH spores produced only gallic acid (92 %), while ellagic acid was not recovered after the fermentation process. Results demonstrated the potential use of these plants as a source for the production of antioxidants.



*Corresponding author:    cag13761@mail.uadec.mx
                                                      ++52 844 4159 534

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