Dissertation > Industrial Technology > Light industry,handicrafts > Food Industry > General issues > Basic science > Food Chemistry > Enzymes

The Study on Breeding and Fermentation Conditions of a Selenium-Riched Yeast and Its Application Research

Author SunPingPing
Tutor ZhangQingQing
School Anhui University of Engineering
Course Microbiology
Keywords selenium yeast mutation response surface selenium methionine selenium soy sauce
CLC TS201.25
Type Master's thesis
Year 2011
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Selenium(Se) is an essential micronutrient that is required in a variety of metabolic functions,and has numerous health effects.The Se content in artificial food is low,the Se content in artificial food can not satisfy people’s require up to snuff,meal Se absorbed in low level has latency menace to human’s health,in order to assure human’s health,and prevent and cure relate disease,the abundant Se absorbed is essential,but inorganic Se can not be used in food because of its higher toxicity.Plants and bacteria have been shown to play a key role in the biological cycle of Se by transformation from inorganic Se to organic Se in the environment.Generally,Se is trace amounts in plants.So it weighs heavily for biosynthesis of large output an cheap Se-enriched organic production by microorganism.This laboratory preserved aroma active dry yeast strains as the starting concentration of Se in microorganisms, mainly as follows:(1) Through the physical and chemical strain mutation, to obtain a height of biomass, high selenium content of strain ZS-Y10. After the strain of mutant ZS-Y10 of the fermentation conditions were optimized, obtained by Plackett-Burman experimental speed, medium volume, pH of the enriched yeast biomass, a greater impact. Response surface and then finalized by the cultivation conditions for high selenium yeast:selenium content of 25ug/ml wort medium, temperature 30℃, initial pH4.75, speed 185r/min, inoculum 10%, medium volume 65mL/250mL, culture time was 40h, the yeast biomass increased to 13.69g/L, selenium content increased to 1310.34ug/g, than the original strain were increased by 65% and 53%.(2) In the optimal fermentation conditions, the yeast mutant ZS-Y10 of glutathione peroxidase activity reached 16.8U, is the strain-3.2 times of active dry yeast. The yeast in the medium containing the growth of Cu2+, its GSH-Px activity than when cultured without added Cu2+is higher. In the medium to add 10-3mol/L of CuSO4, the glutathione peroxidase activity to 68.8U.(3) The use of ultrasonic, enzymatic treatment of yeast were broken to extract the intracellular selenium methionine, and were determined by capillary electrophoresis. The optimum conditions for capillary: 100mmol/L of Tris-phosphate as the running buffer, pH 3.0, separation voltage 25KV, column temperature 20℃, detection wavelength 215nm, 14min Selenomethionine when the peaks and better separation. Selenomethionine concentration in the 5.0~100ug/mL, the concentration and peak area have a good linear relationship. Linear regression equation: Y= 4560X-12447, R2= 0.9995, linear relationship was good. Signal to noise ratio (S/N)= 3, the capillary electrophoresis conditions, the detection of selenomethionine line 0.5ug/mL. Using ultrasonic assisted extraction of enzyme to the yeast cells Selenomethionine, Selenomethionine content of the course have a certain loss of extraction efficiency of 88%, the extraction is better.(4) Yeast ZS-Y10 in the salt content of 15% of the selenium malt extract medium, can growth and metabolism, but has been partially inhibited by 19.0% to the salt can no longer grow, which fully meet the low-salt solid-state fermentation of yeast salt standards. By orthogonal experiment, in adding 15% NaCl medium wort after the initial selenium concentration 20ug/mL, shaker speed 180r/min, pH 5, with volume 50mL/250mL,30℃cultured 40h, yeast ZS-Y10 of the highest biomass. To develop a good solution enriched yeast added to the sauce in the post-mash fermentation aroma, soy sauce, the content of the various basic components has increased, and the total selenium content in soy sauce 1.1 Omg/L, in which content of organic selenium 0.8mg/L.

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