The properties of intracellular b-glucosidases produced from two yeast isolates identified as Hanseniaspora sp. BC9 and Pichia anomala MDD24 were characterized. b-Glucosidase from Hanseniaspora sp. BC9 was not inhibited by both 20% w/v fructose and 20% w/v sucrose and was slightly inhibited by glucose ([ 40% relative b-glucosidase activity with 10% w/v glucose). b-Glucosidase from P. anomala MDD24 was inhibited by glucose, fructose and sucrose. In the presence of 4-12% v/v ethanol, b-glucosidase from P. anomala MDD24 was stimulated in range 110-130% relative activity whereas b-glucosidase from Hanseniaspora sp. BC9 was substantially inhibited in the presence of ethanol. Finally, juice and wine of the Muscat-type grape variety, Traminette, were selected to determine sugar-bound volatile aroma release, particularly terpenes, by the activity of those b-glucosidases. The results showed that high concentration of free aroma compounds were detected from Traminette juice treated with b-glucosidase from Hanseniaspora sp. BC9and Traminette wine treated with b-glucosidase from P. anomala MDD24. The preliminary results with proposed an application of these enzymes in commercial wine production lead to more efficient of b-glucosidase from Hanseniaspora sp. BC9 in releasing desirable aromas during an early stage of alcoholic fermentation while b-glucosidase from P. anomala MDD24 is suitable at the final stage of alcoholic fermentation.

-The production and characterisation of β-glucosidase from an isolated yeast strain classified as a Pichia anomala MDD24 were studied. The result shows that cellobiose is a good inducer for extracellular β-glucosidase production and optimum concentration is 1.5 percent cellobiose in yeast peptone dextrose medium. The purified β-glucosidase from Pichia anomala MDD24 exhibited a specific activity of 614 ± 14 U mg -1 of protein and a molecular mass of 42 kDa. This enzyme was slightly inhibited by fructose and sucrose in the range of 4 to 20% (w/v). An ethanol concentration between 4 and 20% (v/v) activated β-glucosidase activity, at presence 16% (v/v) ethanol, β-glucosidases obtained maximum relative activity around 150%. The optimum pH and optimum temperature for β-glucosidase activity were 4.5 and 40 °C, respectively. Although the activity under the pH and temperature of wine production (pH 3.5-4.0 and 15-20 °C) was quite low, the enzyme was stable and the relative activities were higher than commercial enzyme under those conditions. The extracellular β-glucosidase from Pichia anomala MDD24 makes it possible to release glucosidically-bound monoterpenes, which are the major contributors to floral and fruity aromas in wines from Muscat-type varieties, at final stage of alcoholic fermentation.

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Significance and Impact of the Study: This study demonstrates that yeasts isolated from the ruminal fluid of dairy cattle can utilize lactic acid as a carbon and energy source for growth. The isolated yeasts can be used as probiotic supplements for dairy cattle that are fed highly concentrated diets to reduce ruminal lactic acid production. AbstractRuminal organic acid production, especially lactic acid, can be modified by feeding cattle highly concentrated diets, which have been shown to adversely affect dairy cattle health. Therefore, the use of lactic acid-utilizing organisms is considered to be a potential method for controlling lactic acid levels. This study was conducted to isolate and identify lactic acid-utilizing yeasts from the ruminal fluid of dairy cattle and to determine the specific growth rate and generation time when using lactic acid as a carbon source instead of glucose. Seventeen yeast isolates were examined in this study. Yeasts isolated from dairy cattle that were fed a high cassava pulp diet (HCP) had higher specific growth rates and shorter generation times than yeasts isolated from dairy cattle that were fed a high-concentrate diet (HC) and a mixed diet (M). The three most effective yeasts in terms of specific growth rate and generation time were Pichia kudriavzevii, Candida rugosa and Kodamaea ohmeri, with 99, 100 and 99% nucleotide identities, respectively. These three isolates could be used as potential probiotics in dairy cattle diets.

This study illustrated the ability of T. asahii GSY10 to utilize molasses and (NH4 )2 SO4 for synthesizing and accumulating cellular lipid of which oleic acid (C18:1 ) was predominant. This yeast would be used for microbial lipid production used as feed supplement in dairy cattle.