Production and antioxidative activity of alcoholic beverages made from Thai ou yeast and black rice (Oryza sativa var. Indica cv. Shiun)

Fermentation yeast was isolated from a Thai traditional alcoholic beverage called Thai ou, which is drunk through bamboo tubes. The isolated yeast was identified as a strain of the genus Saccharomyces cerevisiae. The alcoholic beverage made with the isolated yeast designated as S. cerevisiae NP01 from black rice grains had an ethanol concentration of 12.4 to 13.1% (v/v) and a large amount of phenolic compounds. The resulting alcoholic beverages made from black rice grains were red in color, especially those made from uncooked black rice, which had a brilliant red hue similar to that of red or rosé wine. The amount of anthocyanin in the beverages made from uncooked black rice with NP01 and industrial wine yeast W-4 was 118 and 131 μg/ml, respectively. The anthocyanin content of beverages made from uncooked black rice was higher than that of the beverages made from the cooked black rice. The antioxidative activity of alcoholic beverages made from uncooked black rice was also higher than that of beverages made from cooked black rice. In the course of this study, the use of NP01 yeast produced black rice wine that was red in color and exhibited antioxidative activity.Key words: Antioxidative activity, ou, black rice, anthocyanin, alcoholic beverage

Inactivating alternative NADH dehydrogenases: enhancing fungal bioprocesses by improving growth and biomass yield?

Debate still surrounds the physiological roles of the alternative respiratory enzymes found in many fungi and plants. It has been proposed that alternative NADH:ubiquinone oxidoreductases (NADH dehydrogenases) may protect against oxidative stress, conversely, elevated activity of these enzymes has been linked to senescence. Here we show that inhibition of these enzymes in a fungal protein expression system (Aspergillus niger) leads to significantly enhanced specific growth rate, substrate uptake, carbon dioxide evolution, higher protein content, and more efficient use of substrates. These findings are consistent with a protective role of the NADH dehydrogenases against oxidative stress, thus, when electron flow via these enzymes is blocked, flux through the main respiratory pathway rises, leading to enhanced ATP generation. We anticipate that our findings will stimulate further studies in fungal and plant cultures leading to significant improvements in these expression systems, and to deeper insights into the cellular roles of alternative respiration

Oxidative stress in fungal fermentation processes : the roles of alternative respiration

Filamentous fungi are arguably the most industrially important group of microorganisms. Production processes involving these simple eukaryotes are often highly aerobic in nature, which implies these cultures are routinely subject to oxidative stress. Despite this, little is known about how filamentous fungi cope with high levels of oxidative stress as experienced in fermenter systems. More surprisingly, much of our knowledge of oxidative stress responses in fungi comes from environmental or medical studies. Here, the current understanding of oxidative stress effects and cellular responses in filamentous fungi is critically discussed. In particular the role of alternative respiration is evaluated, and the contributions of the alternative oxidase and alternative dehydrogenases in defence against oxidative stress, and their profound influence on fungal metabolism is critically examined. Finally, the importance of further research which would underpin a less empirical approach to optimising fungal strains for the fermenter environment is emphasised