Thinking before the experiment: People have a long history of understanding and using yeast. As early as prehistoric times, people learned how to make wine. About 6,000 years ago, they invented the method of leavening. It was not until the 19th century that people got a glimpse of the true face of drunk yeast. Hans, a Danish contemporary of Pasteur, studied yeast in pure culture and classification. He went deep into yeast in order to find a way to brew high-quality beer.

Purpose requirement

Understand the morphological structure and budding reproduction of yeast.

Utilization of yeast.

Materials and appliances

Yeast culture solution, microscope, dissecting needle, glass slide, cover glass, straw, tweezers, diluted iodine, absorbent paper (or white paper), magnifying glass, gauze.

Method step

Utilization of a yeast

1 Refer to the relevant information about the utilization of yeast: it belongs to a fungus. Its body is round, oval or oval, with nuclei, vacuoles and granular substances in it. It usually reproduces by budding; Some can split in half; Some species can produce ascospores, which are widely distributed in nature, especially in grapes and other fruits and vegetables. They are important fermentation factors, which can decompose carbohydrates to produce alcohol and carbon dioxide, etc. Commonly used in production are baker's yeast, feed yeast, alcohol yeast and wine yeast, etc. Some can synthesize cellulose for medical use, and some are also used for petroleum fermentation. Brewer's yeast belongs to the genus Saccharomyces, and its cells are round, oval or oval, and propagate by budding. It can form ascospores. In fermentation industry, it can be used to produce alcohol or medicinal yeast, and can also be used to extract products such as coagulum, ergosterol, lecithin, coenzyme A and cytochrome C through comprehensive utilization of bacteria.

Connecting with reality, visit Shawan Brewery, get yeast and malt, and bring them back to prepare for the test.

Second, observe the yeast

1.Take a drop of yeast culture solution and make it into temporary tablets. Observe the shape and color of yeast with a microscope.

2. Dye with diluted iodine to observe the cell wall, nucleus, cytoplasm and vacuole of yeast.

3. Draw a yeast that is budding, and note the bud.

Expanding culture of three yeasts

3 strains and culture medium

3. 1 strain: beer yeast

3.2 culture medium

3.2. 1 yeast slant medium

10 wort solid slope, pH5.0

3.2.2 Yeast shake flask seed culture medium

10 wort, pH5.0 or glucose 10%, corn steep liquor 1%, urea 0.2%, ph 5.0.

3.2.3 Yeast batch fermentation medium

After liquefaction and saccharification, the corn flour was converted into glucose concentration 10%, corn steep liquor 1%, ammonium sulfate 0.4%, and pH 5.5.

3.2.4 Yeast fed-batch fermentation medium (discussed by students)

4 experimental instruments and equipment

(1)5 liter fermentor;

(2) bottle shaker or hand crank;

(3) clean bench;

(4) Centrifuge

(5) Microscope

(6) spectrophotometer

(7) triangle bottle.

five

5. 1 batch culture

5. 1. 1 general process

Preparation, sterilization, inoculation and culture of slant culture medium

Required instruments and articles: sterilization pot, test tube, cotton plug, culture medium raw materials, incubator.

300 ml of seed liquid in shake flask, three 500ml triangular flasks, liquid 100ml, culture medium, culture shake flask and gauze.

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Dilute the saccharified liquid of tank culture (double enzyme sugar production) to l0% concentration, add auxiliary materials, sterilize and inoculate.

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Cell separation centrifuge or plate-and-frame filter

5. 1.2 preparation of slant seeds

A ring of yeast was selected from the preservation slant and inoculated into a fresh slant test tube, and cultured in an incubator at 28℃ for 24 hours.

5. 1.3 Preparation of shaking flask seeds

Inoculate the above-mentioned cultivated slant seeds into 500ml sterilized 100ml shake flask seed culture medium, and shake culture 15-20h at 28℃ and 200 rpm.

5. 1.4 fermentor culture

A 5-liter fermentor is filled with 2 liters of fermentation medium, sterilized at 12 1℃ for 20min minutes, cooled to 30℃, and the cultured shake flask seeds are inoculated into the fermentor (inoculation amount is 2-3%) for fermentation. The fermentation conditions are: temperature 28℃,

5. 1.5

0 hour: sampling and measuring total sugar and reducing sugar;

24 hours: sample every 4 hours for microscopic examination, and the concentration of bacteria;

6 experimental time

three days

7 experimental analysis items and methods

(1) yeast microscopy;

(2) determination of yeast concentration (wet weight method): suck 5ml of bacterial liquid, centrifuge at 2500rpm for 5min, remove supernatant, and weigh the wet weight of bacteria.

(3) Determination of fermentation activity

8 experimental report content and data processing

9 experimental results and discussion

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Supplement: The 5-liter fermenter can be replaced by glassware.