introduction to fermentation aspergillus niger and lactobacillus

Introduction to Introduction to FermentationFermentation

Aspergillus niger Aspergillus niger and and Lactobacillus Lactobacillus

Introduction to Introduction to FermentationFermentation

• Aspergillus niger Aspergillus niger and and Lactobacillus Delbruckii Lactobacillus Delbruckii are are the microbes used to commercially produce citric the microbes used to commercially produce citric acid and lactic acid, respectively. The production acid and lactic acid, respectively. The production takes place in a batch fermenter. This tutorial takes place in a batch fermenter. This tutorial will introduce you to the following areas regarding will introduce you to the following areas regarding batch fermentationbatch fermentation– Microbial Growth Kinetics Microbial Growth Kinetics – Media for Industrial Fermentations Media for Industrial Fermentations – SterilizationSterilization– The Development of Inocula for Industrial FermentationsThe Development of Inocula for Industrial Fermentations– Design of a FermenterDesign of a Fermenter– Instrumentation and Control Instrumentation and Control – Aeration and Agitation Aeration and Agitation

Microbial Growth KineticsMicrobial Growth Kinetics• Microbial Growth Kinetics Microbial Growth Kinetics

describe how the microbe describe how the microbe grows in the fermenter. grows in the fermenter. This information is This information is important to determine important to determine optimal batch times. The optimal batch times. The growth of microbes in a growth of microbes in a fermenter can be broken fermenter can be broken down into four stages:down into four stages:– Lag Phase Lag Phase – Exponential PhaseExponential Phase– Stationary PhaseStationary Phase– Death PhaseDeath Phase

(Growth curve is from Shuler (Growth curve is from Shuler p. 161)p. 161)

Microbial Growth KineticsMicrobial Growth Kinetics

• Lag PhaseLag Phase– This is the first phase in the This is the first phase in the

fermentation processfermentation process– The cells have just been injected into a The cells have just been injected into a

new environment and they need time to new environment and they need time to adjust accordinglyadjust accordingly

– Cell growth is minimal in this phase. Cell growth is minimal in this phase.


• Exponential PhaseExponential Phase– The second phase in the fermentation The second phase in the fermentation

processprocess– The cells have adjusted to their The cells have adjusted to their

environment and rapid growth takes environment and rapid growth takes placeplace

– Cell growth rate is highest in this phaseCell growth rate is highest in this phase


• Exponential Phase (Continued)Exponential Phase (Continued)– At some point the cell growth rate will At some point the cell growth rate will

level off and become constantlevel off and become constant– The most likely cause of this leveling off The most likely cause of this leveling off

is substrate limited inhibition is substrate limited inhibition • Substrate limited inhibition means that the Substrate limited inhibition means that the

microbes do not have enough nutrients in microbes do not have enough nutrients in the medium to continue multiplying. the medium to continue multiplying.


• Stationary phaseStationary phase– This is the third phase in the This is the third phase in the

fermentation processfermentation process– The cell growth rate has leveled off and The cell growth rate has leveled off and

become constantbecome constant– The number of cells multiplying equals The number of cells multiplying equals

the number of cells dyingthe number of cells dying


• Death phaseDeath phase– The fourth phase in the fermentation The fourth phase in the fermentation

processprocess– The number of cells dying is greater The number of cells dying is greater

than the number of cells multiplyingthan the number of cells multiplying• The cause of the death phase is usually that The cause of the death phase is usually that

the cells have consumed most of the the cells have consumed most of the nutrients in the medium and there is not nutrients in the medium and there is not enough left for sustainabilityenough left for sustainability

Media for Industrial Media for Industrial FermentationsFermentations

• The media is the feed solutionThe media is the feed solution– It must contain the essential nutrients needed It must contain the essential nutrients needed

for the microbe to growfor the microbe to grow

• Factors of consideration when choosing Factors of consideration when choosing mediamedia

-Quality consistence and availability-Quality consistence and availability

-Ensure there are no problems with Media Prep -Ensure there are no problems with Media Prep or other aspects of production processor other aspects of production process

Ex. Cane molasses, beet molasses, cereal grainsEx. Cane molasses, beet molasses, cereal grains

SterilizationSterilization

• Sterilizing the feed solution is Sterilizing the feed solution is essential because the media cannot essential because the media cannot contain foreign microbes because contain foreign microbes because this could severely hinder the growth this could severely hinder the growth of the production microbeof the production microbe– Most popular method is heat sterilization Most popular method is heat sterilization

of the feed solution of the feed solution

The Development of Inocula for The Development of Inocula for Industrial FermentationsIndustrial Fermentations

• The inoculum is the starter culture that is The inoculum is the starter culture that is injected into the fermenterinjected into the fermenter– It must be of sufficient size for optimal growth It must be of sufficient size for optimal growth

kineticskinetics

• Since the production fermenter in Since the production fermenter in industrial fermentations is so large, the industrial fermentations is so large, the inoculum volume has to be quite largeinoculum volume has to be quite large

- A seed fermenter is usually required to - A seed fermenter is usually required to produce the inoculum volumeproduce the inoculum volume

-The seed fermenter’s purpose is not to -The seed fermenter’s purpose is not to produce product but to prepare inoculumproduce product but to prepare inoculum

Design of a FermenterDesign of a Fermenter• Factors to consider Factors to consider

when designing a when designing a fermenterfermenter– Aseptic and regulatory Aseptic and regulatory

capability, long-term capability, long-term reliabilityreliability

– Adequate aeration and Adequate aeration and agitationagitation

– Low power consumptionLow power consumption– Temperature and pH Temperature and pH

controlscontrols– Sampling facilities Sampling facilities

(14 L fermenter shown is (14 L fermenter shown is a copyright of New a copyright of New Brunswick Scientific)Brunswick Scientific)

Instrumentation and ControlInstrumentation and Control

• The success of a fermentation The success of a fermentation process is highly dependent on process is highly dependent on environmental factorsenvironmental factors– The fermenter needs to be able to The fermenter needs to be able to

control such factors as temperature, pH, control such factors as temperature, pH, and dissolved oxygen levelsand dissolved oxygen levels

Aeration and AgitationAeration and Agitation

• Most industrial fermentations are Most industrial fermentations are aerobic processes meaning that the aerobic processes meaning that the production microbe requires oxygen production microbe requires oxygen to growto grow– The oxygen demand is met by sparging The oxygen demand is met by sparging

air through the fermentation vessel and air through the fermentation vessel and using an agitator increase the amount of using an agitator increase the amount of dissolved oxygendissolved oxygen

ReferencesReferences

• Stanbury, P.F., A. Whitaker, and S. J. Stanbury, P.F., A. Whitaker, and S. J. Hall, Hall, Principles of Fermentation Principles of Fermentation TechnologyTechnology, 2, 2ndnd ed., Butterworth ed., Butterworth Heinemann, Oxford, 2000.Heinemann, Oxford, 2000.

• Shuler, M. L. and F. Kargi. Shuler, M. L. and F. Kargi. Bioprocess Bioprocess Engineering Basic ConceptsEngineering Basic Concepts, 2, 2ndnd ed., ed., Prentice Hall, Upper Saddle River, NJ, Prentice Hall, Upper Saddle River, NJ, 2002. 2002.

introduction to fermentation aspergillus niger and lactobacillus

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