Yeast Pre-Lab

Yeasts’ capability of undergoing ethanol fermentation, its ability to ferment other sugars and artificial sweeteners, and how lactase influences yeasts ability to use lactose as a food source Kristina Naydenova Father Michael Goetz Purpose Part A: To investigate whether yeast has the ability to ferment glucose to produce carbon dioxide gas and ethanol. Part B: To investigate whether yeast has the ability to ferment other sugars and artificial sweeteners and how lactase influences their ability to use lactose as a food source. Question

Part A: Does yeast have the ability of undergoing ethanol fermentation? Part B: Does yeast have the ability to ferment other sugars and artificial sweeteners? Does lactase influence the ability of yeast to use lactose as a food source? Hypothesis Part A: If yeast produces carbon dioxide gas (the solution will turn cloudy due to carbon dioxide presence) and ethanol after fermenting glucose then it has the ability to undergo ethanol fermentation because ethanol fermentations reactants consist of glucose and the products consist of carbon dioxide gas and ethanol.

Part B: If yeast has the ability to ferment other sugars and artificial sweeteners then the products of the solution will consist of carbon dioxide gas and ethanol because the products of ethanol fermentation are carbon dioxide gas and ethanol. If lactase influences the ability of yeast to use lactose as a food source then the yeast will be able to use lactose to produce carbon dioxide gas and ethanol because the yeast will be capable of breaking down lactose into glucose and galactose. Materials * Safety goggles| * Lab apron| 4 flasks (100 mL) and 1 stopper| * Wax pencil (for making test tubes)| * Ruler| * 6 large beakers (400 mL)| * Thermometer| * Stopwatch| * 50 mL glucose suspension (10%)| * 50 mL yeast suspension (I package per 100 mL of water)| * Cotton batting| * Limewater| * Warm water (35 °C)| * 10 mL of each of the following solutions: glucose, sucrose, lactose, and artificial sweetener (10%)| * 10 mL of a suspension of lactose (10%) with a pinch of lactase| * 10 mL of distilled water| * Graduated cylinder| * 6 test tubes (15 mL) with 1 hole rubber stoppers|

Variables Procedure 1. The safety goggles and lab apron were put on. 2. Three flasks were labeled as “yeast and glucose,” “yeast,” and “glucose. ” 3. 10 mL of glucose solution and 5 mL of yeast suspension were added to the “yeast and glucose” flask. 4. 10 mL of distilled water with 5 mL of yeast suspension to the “yeast and glucose” flask as a control. 5. 5 mL of distilled water with 10 mL of glucose solution were added to the “glucose” flask as a second control. 6. Cotton batting was placed in the mouth of the flasks to reduce air turbulence. . The cotton batting was removed carefully after 24 hours and the contents of each flask were smelled. A slight alcohol odour was detected. 8. Each flask was tested for the presence of carbon dioxide.

The invisible gas mixture was slowly poured into a flask that contains 25 mL of limewater. The limewater flask was stoppered and the contents were swirled to mix the limewater with the gas. Observations were recorded. The flask was rinsed. 25 mL of fresh limewater was added before testing the next gas sample. . A ruler was used to place graduation marks at 0. 5 cm intervals along the sides of the test tubes. 10. Six beakers of warm water (35 °C) were prepared. The beakers were two-thirds full of warm water. 11. The six test tubes were labeled as “glucose,” “sucrose,” “lactose free milk,” “artificial sweetener (Splenda),”lactose free milk and lactase,” and “distilled water”. 12. 10 mL of the appropriate solutions to each test tube were added. 13. 5 mL of yeast suspension to each test tube were added.

The test tubes were filled. 14. The test tubes were scaled with one-hole stoppers after the mixtures are placed in the test tubes. 15. One test tube was held. The holes in the stopper were covered, and the test tube was inverted and placed into a beaker of warm water. The process was repeated for all six solutions, using a different beaker for each solution. 16. The amount of gas produced after 1, 5 and 10 minutes was recorded using the graduation marks on the test tubes. Observations Table 1.

Before and after observations of yeast and glucose, yeast and glucose Solution| Before| After| Yeast and glucose| | | Yeast| | | Glucose | | | Table 2. The amount of gas produced by glucose, sucrose, lactose free milk, artificial sweetener, lactose free milk and lactase, and distilled water after 1, 5 and 10 minutes Solution| Time (1 minute)| Amount of gas| Time (5 minutes)| Amount of Gas| Time (10 minutes)| Amount of Gas| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |