BAKER’S YEAST PRODUCTION

AN OVERVIEW

A SCHEMATIC FLOW DIAGRAM FOR THE PRODUCTION OF BAKER’S YEAST

For compresse

d

For ADY

Filter press

Filter press

Mixer & extruder

Extruder

Packaging

Dryer

Storage

3-5C

Cool storage

Consumer

Packaging

Bulk

Ammonia

H3PO4Mineral

s

Vitamins

De

former

F 3

F 4

Wort storage

Beet CaneChemicals

Mixer Clarifier

F 1F 2

PC

Pasteur flask

Aeration

Air blower

Culture

Wash & Storage

Cooler

Separator

CELL DIVISION BY BUDDING

MOTHER MOTHER CELLCELL

BUD INNITIATIONBUD INNITIATION

DNADNA

DNA DNA DUPLICATIODUPLICATIONN

BUD BUD ENLARGEMENT, ENLARGEMENT, NUCLEAR NUCLEAR MIGRATIONMIGRATION

DAUGHTER CELLDAUGHTER CELL

MOTHER MOTHER CELLCELL

(NUCLEUS)(NUCLEUS)

BUD SCARBUD SCAR

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

OXYGENCARBON SOURCE

NITROGEN SOURCE

CHROMOSOME DOUBLING BEFORE

CELL DIVISIONMICRO

NUTRIENTS

PHOSPHATE SOURCE

Daughter cell

Mother cell

Bud scar

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

GLUCOSE

PYRUVATE

ETHANOL

AcetaldehydeAt low O2 or

high glucose

At high O2

and/or low glucose

Glycolysis

AS IN A WINE FERMENTATION

2ATP

A decision point for carbon flow depending on oxygen tension and sugar in the

medium

AS WITH CELL PROPAGATION36ATP

ANAEROBIC AEROBIC

METABOLIC FATE OF GLUCOSE AS DICTATED BY FEED RATE AND OXYGEN (AIR)

GLUCOSE

PYRUVATE

ETHANOL

Acetaldehyde At low O2 or

high glucose

TCA

CYCLE

At high O2

and/or low glucose

BIOMASS

Glycolysis

PROPOSED PATHWAY FOR THE PROPOSED PATHWAY FOR THE PRODUCTION OF BIOMASS FROM CORN PRODUCTION OF BIOMASS FROM CORN

SYRUPSYRUP

- ketoglutarate

Succinate

Fumarate

Malate

Oxaloacetate

3ATP

3ATP

3ATP

3ATP

Acetyl CoA

Pyruvate

GLUCOSE

TCA CYCLE

ATPEnergyBIOMASS

CO2

O2

8ATP CO2

CO2

Precursors

Citrate

Glucose + O2 + N + P + Nutrients Biomass + CO2 + 38ATP

Ethanol

Feed-back

control O2

3ATP

Conditions that favor formation of volatiles during propagation of Torula

Yeast

Ethanol

Acetaldehyde

Acetate

Acetyl CoA

Ethyl acetate

Ethanol

CoA

FeO2

Low O2

Low Fe

Low O2

Low Fe

Low O2

Low Fe ADH

Acetaldehyde

Acetate

Ethyl acetate

TCA

CYCLE

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 BASISHENCE, HIGHER AMOUNTS NEEDED

BETTER STORAGE STABILITY AT ROOM TEMPERATURE

SIGNIFICANT SAVING ON TRANSPORTATION COSTS

SPECIAL REHYDRATION PROCEDURES NEEDED

EFFECT OF TREHALOSE DURING DRYING

Cell wall

of compressed yeast

DRYING

Membrane

Dry cell wall

Leaky membrane

Trehalose effect

A more stable

membrane

DRYING

Lipids

Proteins

Shrunken Protein

1 2 3

OUT

INSIDE

YEAST

CELL

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

H+H+

H+

H+

pH remains steady

pH gets lowered

ACID INTOLERANCE

Example: BacteriaACID TOLERANCE

Example: Yeast

Proton Pump

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

Bacteria 3 6 12 24 48 96 192

Time 0 20 40 60 80 100 120

(Minutes)

Yeast 40 80

Generation time for yeast: 100 minutes

Generation time for bacteria: 20 minutes

PROBABLE MECHANISM IN THE INDUCTION OF ENZYMES TO UTILIZE A NEW SUBSTRATE

Gene

Transcription

translation

DNAMessenger

RNA

Polypeptide chain

Coiling

ETHANOL

PYRUVATE

Enzyme

ATP ATP

ATP

TCA

cycle

EXAMPLE: A CHANGE FROM GLUCOSE TO

ETHANOL

Tilak 11.4.04

[> 30 MINUTES]

Template

BREAKDOWN OF SUGAR DURING WINE FERMENTATION

O

CH2OH

H

OH

OH

OHOH

H

H

C C OH

H

H

H H

H

CO

O

H

HOGlucose

(Corn Syrup)

Ethanol

Carbon dioxide

WaterC6H12O6 ; MW=180

C2H5OH; MW=46

CO2; MW =44

H2O; MW =18

C6H12O6 2[C2H5OH] + 2[CO2] + 57 kcal (2ATP)

Wine Fermentatio

n 180 92 88

BREAKDOWN OF SUGAR DURING YEAST PROPAGATION

O

CH2OH

H

OH

OH

OHOH

H

H

C C OH

H

H

H H

H

CO

O

H

HOGlucose

(Corn Syrup)

Ethanol

Carbon dioxide

WaterC6H12O6 ; MW=180

C2H5OH; MW=46

CO2; MW =44

H2O; MW =18

C6H12O6 + 6[O2] BIOMASS + 6[H2O] + 6[CO2] + 686 kcal

Baker’s propagation

180 192 108 264 (38ATP)