BAKER’S YEAST PRODUCTION AN OVERVIEW

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

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

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)

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

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

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

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)

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

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

PROPOSED PATHWAY FOR THE PRODUCTION OF BIOMASS FROM CORN SYRUP Glucose + O2 + N + P + Nutrients Biomass + CO2 + 38ATP 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

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

TYPICAL COMPOSITION OF CREAM OR COMPRESSED YEAST (ON SOLIDS BASIS) PROTEIN (N X 6.25) 52% CARBOHYDRATES 30% MINERALS 8% NUCLEIC ACID 5% LIPIDS 4% OTHERS 1%

ACTIVE DRY YEAST

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

EFFECT OF TREHALOSE DURING DRYING 1 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

CRITICAL CONTROL POINTS IN THE PRODUCTION OF ACTIVE DRY YEAST LOWER % NITROGEN AIMED IN THE YEAST - GENERALLY IN THE 6.5 - 7% 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 0.2 - 0.3 CM DRY IN TRAY DRYER (P & S DRYER)

INSTANT ACTIVE DRY YEAST

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

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

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

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 5 - 8 times faster than yeast Under conditions where yeast growth is suppressed, bacteria can gain dominance, instantaneously

PROBABLE WAY THE CELLS INCREASE AFTER pH TREATMENT Generation time for yeast: 100 minutes Generation time for bacteria: 20 minutes Yeast 40 80 Bacteria 3 6 12 24 48 96 192 Time 0 20 40 60 80 100 120 (Minutes)

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 11.4.04

BREAKDOWN OF SUGAR DURING WINE FERMENTATION C6H12O6 2[C2H5OH] + 2[CO2] + 57 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

BREAKDOWN OF SUGAR DURING YEAST PROPAGATION Baker’s propagation C6H12O6 + 6[O2] BIOMASS + 6[H2O] + 6[CO2] + 686 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