Respiration And Respiration Of Yeast

WEEK 3

PRACTICAL 3

3.1 : METABOLISM – FERMENTATION AND RESPIRATION IN YEASTS

INTRODUCTION

Yeasts are facultative anaerobes. They are able to metabolize the sugars in two different ways which is aerobic respiration in the presence of oxygen and anaerobic respiration in the absence of oxygen. The aerobic respiration also known as cellular respiration takes place when glucose is broken down in the present of oxygen to yield carbon dioxide, water and energy in the form of ATP. While in anaerobic respiration, fermentation takes place because it occurs in the absence of external electron acceptor. Because every oxidation has to be coupled to a reduction of compound derived from electron donor. On the other hand, in cellular respiration an exogenous

To observe the growth and pH of the yeast provided. To determine suitable media for the certain yeasts strains to grow. To compare differences in characteristics of yeast strains in different cultures.

MATERIALS AND APPARATUS

3.1 : Metabolism – Fermentation and Respiration inYeasts

Culture plates of yeasts strains: S41, a pet 1 and M240, conical flasks containing Yeast Extract Potassium Acetate (YEPA), Yeast Extract Peptone Dextrose (YEPD) and Yeast Extract Palm Olein (YEPPO) media, pH indicator, inoculation loop, microscope, methylene blue, Bunsen burner and incubator.

PROCEDURE By using an inoculating loop, one loop of S41 is inoculated into 2 conical flasks of YEPA broth, YEPD broth and YEPPO broth respectively. Step 1 is repeated by using different yeast strains, a pet 1 and M240 into all 6 conical

Also known as alcoholic fermentation, this process is occurs in an anaerobic environment. In alcoholic fermentation, glucose molecules are degraded into two molecules of ethanol and two molecules of carbon dioxide. In production of alcohol, first, glycolysis process will breakdown glucose molecule into to pyruvic acid. Then, carboxyl group of the pyruvic acid will be removed and causing carbon dioxide to be excreted. The NADH then left its hydrogen onto the second carbon molecule creating ethanol. The overall chemical reaction are as follows :

C6H12O6 + 2 ADP + 4 H+ → 2 C2H5OH + 2 CO2 + 2 ATP + 2 H2O glucose ethanol energy The most important alcoholic fermentation in industry is wine. It is produced by fermentation of fruit juice. Beer or ale is also one of the important alcoholic fermentation that is produced by fermentation of malted grains and distilled beverage, produced by concentrating alcohol from fermentation by distillation.

OBJECTIVES To observe alcohol production of yeast. To determine the biochemistry involved in alcohol production of