1. BAKER’S YEAST PRODUCTION AN OVERVIEW

2. A SCHEMATIC FLOW DIAGRAM FOR THE PRODUCTION OF BAKER’S YEAST
Chemicals
Beet
Cane PC
Ammonia
F 1
F 2
Culture
Pasteur flask
Minerals
Vitamins De
former
H3PO4
Mixer
Clarifier
Aeration
Air blower
F 3
Wort storage
Cooler
Wash & Storage
F 4
Separator
Mixer & extruder
Packaging
Storage
3-5C
For compressed
Filter press
Consumer
Packaging
Bulk
For ADY
Filter press
Extruder
Dryer
Cool storage

3. CELL DIVISION BY BUDDING
(NUCLEUS)
BUD INNITIATION
DAUGHTER CELL
DNA
BUD SCAR
MOTHER CELL
DNA DUPLICATION
BUD ENLARGEMENT, NUCLEAR MIGRATION
MOTHER CELL

4. BASIC REQUIREMENTS FOR CELL DIVISION
‡ Carbon matrix to build the structure (glucose or ethanol)
‡ Nutrients to produce bio-molecules (O2, P, N, micro nutrients, Trace elements, etc)
‡ Energy source to drive the biological systems (Glucose or Ethanol)

5. PREREQUISITS FOR BUDDING OR CELL DIVISION
Bud scar
OXYGEN
CARBON SOURCE
PHOSPHATE SOURCE
Mother cell
NITROGEN SOURCE
CHROMOSOME DOUBLING BEFORE CELL DIVISION
MICRO
NUTRIENTS
Daughter cell

6. LIFE NEEDS ENERGY TO CARRY OUT ITS TASKS ATP - LIFE’S BATTERY
POWER BEHIND LIFE
LIFE NEEDS ENERGY TO CARRY OUT ITS TASKS
ATP - LIFE’S BATTERY
IT’S THE ENERGY CURRENCY MOLECULE OF CELL
GLUCOSE OR ETHANOL AT HIGH OXYGEN TENSION PROVIDES THE NECESSARY ATP TO DRIVE ALL REACTIONS INCLUDING CELL DIVISION

7. HOW YEAST BEHAVES UNDER AEROBIC VS ANAEROBIC CONDITIONS
ANAEROBIC (No Oxygen):
Alcoholic fermentations, Example: wine or beer
fermentations
AEROBIC (In the presence of Oxygen)
Yeast propagation

8. CRITICAL DIFFERENCE IN ATP GENERATION
Alcohol production via anaerobic conditions utilize one pathway
ATP produced by anaerobic pathway is low (2ATPs)
Biomass production via aerobic conditions utilize another pathway
ATP production via aerobic pathway is high (38ATP)

9. METABOLIC FATE OF GLUCOSE UNDER ANAEROBIC VS AEROBIC CONDITIONS
2ATP
Glycolysis
At high O2 and/or low glucose
PYRUVATE
AS WITH CELL PROPAGATION
36ATP
Acetaldehyde
At low O2 or
high glucose
A decision point for carbon flow depending on oxygen tension and sugar in the medium
ETHANOL
AS IN A WINE FERMENTATION

10. METABOLIC FATE OF GLUCOSE AS DICTATED BY FEED RATE AND OXYGEN (AIR)
Glycolysis
At high O2 and/or low glucose
TCA
CYCLE
PYRUVATE
Acetaldehyde
At low O2 or
high glucose
ETHANOL
BIOMASS

11. PROPOSED PATHWAY FOR THE PRODUCTION OF BIOMASS FROM CORN SYRUP
Glucose + O2 + N + P + Nutrients Biomass + CO ATP
GLUCOSE
Feed-back control
3ATP
 - ketoglutarate
8ATP O2
CO2
3ATP
Citrate
CO2
TCA CYCLE
CO2
Succinate
Pyruvate
Acetyl CoA O2
3ATP
Ethanol
3ATP
Oxaloacetate
Fumarate
Precursors
3ATP
Malate
BIOMASS
Energy
ATP

12. O2 Ethanol Ethanol Acetaldehyde Ethyl acetate Acetate CoA Acetyl CoA
Conditions that favor formation of volatiles during propagation of Torula Yeast
Ethanol
Acetaldehyde
Ethanol
Low O2
Low Fe
ADH
Acetaldehyde
Low O2
Low Fe
Ethyl acetate
Ethyl acetate
TCA
CYCLE
Acetate O2 Fe
Low O2
Low Fe
CoA
Acetyl CoA
Acetate
Excessive contaminants also contribute to higher level of volatiles thereby affecting yields

13. TYPICAL COMPOSITION OF CREAM OR COMPRESSED YEAST (ON SOLIDS BASIS)
PROTEIN (N X 6.25) 52%
CARBOHYDRATES 30%
MINERALS 8%
NUCLEIC ACID %
LIPIDS %
OTHERS 1%

14. ACTIVE DRY YEAST

15. CHARACTERISTICS OF ACTIVE DRY YEAST
SPECIAL STRAINS WITH HIGH TREHALOSE ACCUMULATION USED TO WITHSTAND DRYING CONDITIONS
MOISTURE CONTENT IN THE 3-7% RANGE
YEAST LESS ACITVE THAN COMPRESSED ON EQUAL SOLIDS BASIS
HENCE, HIGHER AMOUNTS NEEDED
BETTER STORAGE STABILITY AT ROOM TEMPERATURE
SIGNIFICANT SAVING ON TRANSPORTATION COSTS
SPECIAL REHYDRATION PROCEDURES NEEDED

16. EFFECT OF TREHALOSE DURING DRYING1
YEAST CELL 2 3
Proteins
Shrunken Protein
Lipids
OUT
DRYING
DRYING
Trehalose effect
INSIDE
Membrane
Leaky membrane
A more stable membrane
Cell wall
of compressed yeast
Dry cell wall

17. CRITICAL CONTROL POINTS IN THE PRODUCTION OF ACTIVE DRY YEAST
LOWER % NITROGEN AIMED IN THE YEAST
- GENERALLY IN THE % RANGE
LESS PHOSPHERIC ACID TO COMPENSATE REDUCED AMMONIA
END BUD INDEX TO BE LESS THAN 2%
- CONTROL FEED AT END TO LIMIT BUDDING(MATURATION)
EXTRUDE COMPRESSED YEAST TO CM
DRY IN TRAY DRYER (P & S DRYER)

18. INSTANT ACTIVE DRY YEAST

19. CHARACTERISTICS OF INSTANT ACTIVE DRY YEAST
PRODUCTION PROCEDURE PARALLELS ADY PROCEDURE
SPECIAL STRAINS USED FOR HIGHER ACTIVITY AND DRYABILITY
LOW NITROGEN AIMED IN YEAST
NO SPECIAL REHYDRATION PROCEDURE NECESSARY
NOODLES MADE THINNER TO IMPROVE REHYDRATION
GENERALLY VACUUM PACKED TO RETAIN STABILITY

20. CRITICAL CONTROL POINTS IN THE PRODUCTION OF INSTANT ADY
UP STREAM PROCESSING PARALLELS ADY PROCESS UP TO POINT OF CAKE PRODUCTION
THINNER NOODLES TO INCREASE SURFACE AREA OF PELLETS
EMULSIFIER TO IMPROVE EXTRUSION
DRY BY A MORE GENTLE AIR LIFT DRYING PROCESS
USE VACUUM PACK TO MAINTAIN STABILITY FOR LONGER PERIODS

22. MECHANISM OF ACID TOLERANCE IN THE MICROBIAL WORLD
Proton Pump H+
pH gets lowered
pH remains steady H+ H+
ACID INTOLERANCE
Example: Bacteria
ACID TOLERANCE
Example: Yeast

23. BACTERIA VS YEAST - MAJOR DIFFERENCES
Yeast produces ethanol at low oxygen and biomass at high oxygen. Bacteria does not follow this rule. Hence, bacteria can proliferate more easily.
Aerobic bacteria grow fast and anaerobic bacteria grow slower under high O2 tension. The opposite occurs at low O2 tension
Growth rate of bacteria is times faster than yeast
Under conditions where yeast growth is suppressed, bacteria can gain dominance, instantaneously

24. PROBABLE WAY THE CELLS INCREASE AFTER pH TREATMENT
Generation time for yeast: minutes
Generation time for bacteria: 20 minutes
Yeast
Bacteria
Time
(Minutes)

25. EXAMPLE: A CHANGE FROM GLUCOSE TO ETHANOL
PROBABLE MECHANISM IN THE INDUCTION OF ENZYMES TO UTILIZE A NEW SUBSTRATE
EXAMPLE: A CHANGE FROM GLUCOSE TO ETHANOL
ETHANOL
Transcription
translation
Coiling
ATP
ATP
ATP
Enzyme
Polypeptide chain
Template
Messenger RNA
Gene
DNA
PYRUVATE
[> 30 MINUTES]
TCA
cycle
Tilak

26. BREAKDOWN OF SUGAR DURING WINE FERMENTATION
C6H12O [C2H5OH] + 2[CO2] kcal (2ATP)
180 92 88 O C O
CH2OH H H
Carbon dioxide H O H
CO2; MW =44 H C C OH OH H H OH OH H OH
Ethanol H
C2H5OH; MW=46 O
Glucose
(Corn Syrup) H
Water
C6H12O6 ; MW=180
H2O; MW =18

28. BREAKDOWN OF SUGAR DURING YEAST PROPAGATION
Baker’s propagation
C6H12O [O2] BIOMASS + 6[H2O] + 6[CO2] kcal
(38ATP)
180
192
108
264 O C O
CH2OH H H
Carbon dioxide H O H
CO2; MW =44 H C C OH OH H H OH OH H OH
Ethanol H
C2H5OH; MW=46 O
Glucose
(Corn Syrup) H
Water
C6H12O6 ; MW=180
H2O; MW =18