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Factors Affecting Volatile Phenol Production During Fermentations with Pure and Mixed Cultures of Dekkera bruxellensis and Saccharomyces cerevisiae

Janez Kosel, Neža Čadež and Peter Raspor1*


University of Ljubljana, Biotechnical Faculty, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia

1
Current address: University of Primorska, Faculty of Health Sciences, Polje 42, SI-6310 Izola, Slovenia


Article history
:
Received July 17, 2013

Accepted February 4, 2014

Key words:

Saccharomyces cerevisiae
, Dekkera bruxellensis, wine fermentation, volatile phenols


Summary:

The paper examines the impact of ethanol, and hidroxycinnamic and vinylphenol precursors
on the production of volatile phenols in fermentations of mixed and pure cultures of yeasts Saccharomyces cerevisiae and Dekkera bruxellensis. Three different D. bruxellensis strains were examined and they all showed a unique volatile phenol production pattern in the fermentations of pure and mixed cultures. Generally, the results showed that in mixed culture fermentations less vinylphenols and more ethylphenols were produced in comparison with D. bruxellensis pure culture fermentations. Vinylphenol precursors significantly inhibited the growth of S. cerevisiae and the production of ethylphenols. Nevertheless, it was found that D. bruxellensis genes encoding for enzymes coumaric acid decarboxylase (CAD) and vinylphenol reductase (VPR) are more responsive to vinylphenol precursors in  comparison with hidroxycinnamic acids. Consequently, higher concentrations of vinylphenols in the cell were found to be more cytotoxic than hidroxycinnamic acids. In general, low ethanol concentrations induced higher production of volatile phenols by S. cerevisiae and D. bruxellensis. This was confirmed with the expression pattern of gene encoding for CAD of D. bruxellensis.


*Corresponding author:      peter.raspor@fvz.upr.si

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Microbial Anchoring Systems for Cell-Surface Display of Lipolytic Enzymes


Ana Bielen, Renata Teparić, Dušica Vujaklija2* and Vladimir Mrša1*


1
Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6,
HR-10000 Zagreb, Croatia
2Division of Molecular Biology, Institute Ruđer Bošković, Bijenička 54, HR-10000 Zagreb, Croatia


Article history
:
Received January 17, 2014
Accepted March 3, 2014

Key words:

surface display, genetic immobilization, lipolytic enzymes, bacterial envelope, yeast cell wall

Summary
:                                                                                                                                                                                
Studies of microbial cell envelopes and particularly cell surface proteins and mechanisms
of their localization brought about new biotechnological applications of the gained knowledge in surface display of homologous and heterologous proteins. By fusing surface proteins or their anchoring domains with different proteins of interest, their so-called genetic immobilization is achieved. Hybrid proteins are engineered in a way that they are expressed in the host cells, secreted to the cell surface and incorporated into the wall/ envelope moiety. In this way, laborious and often detrimental procedure of chemical immobilization of the protein is avoided by letting the cells do the whole procedure. Both bacterial and yeast cells have been used for this purpose and a number of potential biotechnological applications of surface-displayed proteins have been reported. Among the most frequently used passenger proteins are lipolytic enzymes, due to their great technological significance and numerous important applications. In this review, our current knowledge on mechanisms and molecular systems for surface display of lipolytic enzymes on bacterial and yeast cell surfaces is summarized.

 

 

*Corresponding author:      vujaklij@irb.hr, vmrsa@pbf.hr

§
Both authors contributed equally to this paper


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Brief Note on the Development of Biotechnology

Karl Bayer

Department of Biotechnology, University of Natural Resources and Life Sciences,
Muthgasse 18, A-1190 Vienna, Austria

Article history:

Received April 10, 2013

Accepted September 23, 2013

Key words:
molecular biotechnology, biopharmaceuticals, PAT, QbD

Summary:

Biotechnology, with the main applications in food and nutrition, dates back to the early
times of mankind. In the recent decades the progress in natural sciences, mathematics and computer science has led to a new branch termed molecular biotechnology, which finally developed as an autonomous scientific discipline. The field of biotechnology, in the past generally empirically driven, now largely benefits from molecular biotechnology by improved systems, knowledge and understanding. Thereby, compliance with the recently published initiatives of the regulatory authorities to accelerate the approval process for the manufacturing of biopharmaceuticals can be gained.


*Corresponding author:        karl.bayer@boku.ac.at

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Membrane Transport Inhibition as Mode of Action of Polyene Antimycotics: Recent Data Supported by Old Ones

Miroslava Opekarová1 and Widmar Tanner2*


1
Institute of Microbiology, Academy of Sciences of the Czech Republic, CZ-14220 Prague, Czech Republic

2Institute of Cell Biology and Plant Physiology, University of Regensburg, DE-93053 Regensburg, Germany

Article history:

Received March 29, 2013

Accepted September 23, 2013


Key words:

amphotericin B, nystatin, natamycin, sugar and amino acid transport

Summary:

Recent studies demonstrate that the actual interactions of polyenes with membrane
sterols are the basis for their antimycotic toxicity and not, as previously assumed, their potentialb to form pores. Therefore, sterols must play a vital role in membranes and this function is seriously disturbed once polyenes bind to and/or sequester them. Essential membrane proteins obviously require sterols for their activity. Among the various membrane protein/ergosterol interactions discussed herein, transport proteins of the plasma membrane are most likely the primary target for polyenes. All data available which support this notion are summarized in this review. Even data obtained almost 40 years ago could be useful in guiding future research.


*Corresponding author:        widmar.tanner@biologie.uni-regensburg.de

                                           

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