Chemical and volatile composition of Pálinka produced using different commercial yeast strains of Saccharomyces cerevisiae.

Pálinka is Hungarian traditional alcoholic drink, and its quality is strongly depending on applied yeast strain. Unfortunately, all commercial yeast strains used the production of pálinka are selected for oenological purpose, and thus the efficacy and aroma releasing capacity are vary depending on the type and quality of fruit used. In this study, the fermentation efficacy of nine commercial yeast strains of Saccharomyces cerevisiae was focused. All strains were able to do alcoholic fermentation of apple juice quite efficiently, and the simple sugars (fructose, glucose and sucrose) were almost exhausted at the end of fermentation. Meanwhile, the alcohol production capacity and yield were no significant differences (around 9.17 v/v %-9.43 v/v %), whereas the ability of sugar consumption of strains Uvaferm Danstil A and Fermicru AR2 was stronger than others. The differences in the concentration and composition of volatile compounds were recorded. The highest levels of total volatile compounds were observed in samples fermented with Uvaferm Danstil A, Fermiblanc Arom, Vin-O-Ferm Roses, and Fermicru AR2. Meanwhile total volatile compounds, 2-methyl-1-propanol, 3-methyl-1-butanol, total higher alcohols, ethyl acetate, and total esters were considered as key parameters for describing the profile of fermented apple juices, whereas total fusel alcohols, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, and total volatile compounds were characteristic indicators of samples fermented with Uvaferm Danstil A. This work provides very good information of commercial yeast strains for industrial pálinka production.

Formation of novel hydrogel bio-anode by immobilization of biocatalyst in alginate/polyaniline/titanium-dioxide/graphite composites and its electrical performance.

A new bio-anode containing gel-entrapped bacteria in alginate/polyaniline/TiO2/graphite composites was constructed and electrically investigated. Alginate as dopant and template as well as entrapped gel was used for immobilization of microorganism cells. Increase of polyaniline concentration resulted an increase in the conductivity in gels. Addition of 0.01 and 0.02 g/mL polyaniline caused 6-fold and 10-fold higher conductivity, respectively. Furthermore, addition of 0.05 g/mL graphite powder caused 10-fold higher conductivity and 4-fold higher power density, respectively. The combination of polyaniline and graphite resulted 105-fold higher conductivity and 7-fold higher power-density output. Optimized concentrations of polyaniline and graphite powder were determined to be 0.02 g/mL and 0.05 g/mL, respectively. Modified hydrogel anode was successfully used in microbial fuel cell systems both in semi- and continuous operations modes. In semi-continuous mode, about 7.88 W/m3 power density was obtained after 13 h of fermentation. The glucose consumption rate was calculated to be about 7 mg glucose/h/1.2·107 CFU immobilized cells. Similar power density was observed in the continuous operation mode of the microbial fuel cell, and it was operated stably for more than 7 days. Our results are very promising for development of an improved microbial fuel cell with new type of bio-anode that have higher power density and can operate for long term.

Novel method for screening microbes for application in microbial fuel cell.

The ability to produce and to transport exo-electrons by microbes either to external acceptors or to electrodes are reported in our study. All investigated microorganisms (exception of Lactobacillus plantarum) exhibited strong iron-reducing capabilities in the absence of mediator meaning production and secretion of exo-electrons to the growth medium. L.plantarum, Saccharomyces cerevisiae and Escherichia coli need an electron shuttle molecule to reduce Fe(3+) ion. Significant correlation was observed between growth and iron-reducing capacity, as well as between initial cell counts and iron-reducing capacity. Changes of bio-current generated in MFC and iron-reduction were experimentally monitored, and a mathematical model was established by regression analysis. Based on these results, a novel and rapid screening method was developed for the selection of microorganisms for potential application in MFC. The method is based on the measurement of absorbance of bacterial and yeast cultures at 460 nm, providing a robust and high sample throughput approach.

A novel thermostable alpha-galactosidase from the thermophilic fungus Thermomyces lanuginosus CBS 395.62/b: purification and characterization.

High levels of an extracellular alpha-galactosidase are produced by the thermophilic fungus Thermomyces lanuginosus CBS 395.62/b when grown in submerse culture and induced by sucrose. The enzyme was purified 114-fold from the culture supernatant by (NH(4))(2)SO(4) fractionation, and by chromatographical steps including Sepharose CL-6B gel filtration, DEAE-Sepharose FF anion-exchange, Q-Sepharose FF anion-exchange and Superose 12 gel filtration. The purified enzyme exhibits apparent homogeneity as judged by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and iso-electric focusing (IEF). The native molecular weight of the monomeric alpha-galactosidase is 93 kDa with an isoelectric point of 3.9. The enzyme displays a pH and temperature optimum of 5-5.5 and 65 degrees C, respectively. The purified enzyme retains more than 90% of its activity at 45 degrees C in a pH range from 5.5 to 9.0. The enzyme proves to be a glycoprotein and its carbohydrate content is 5.3%. Kinetic parameters were determined for the substrates p-nitrophenyl-alpha-galactopyranoside, raffinose and stachyose and very similar K(m) values of 1.13 mM, 1.61 mM and 1.17 mM were found. Mn(++) ions activates enzyme activity, whereas inhibitory effects can be observed with Ca(++), Zn(++) and Hg(++). Five min incubation at 65 degrees with 10 mM Ag(+) results in complete inactivation of the purified alpha-galactosidase. Amino acid sequence alignment of N-terminal sequence data allows the alpha-galactosidase from Thermomyces lanuginosus to be classified in glycosyl hydrolase family 36.