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Methodsofscreening,culturing,improvementandstorageofmicroorganisms...
environment.Intheaccelerationphase,thereisanincreasing
growthintheamountofbiomassuntilitreachesanexponential
rate(exponentialphaseorlogarithmicgrowth).
Duringthisstagethegrowthofthemicroorganismreaches
itshighestvalue.Aftersometimethegrowthsubstrateinthe
culturesystemisexhaustedandtoxicmetabolicproductsmay
appear,sothemultiplicationofthemicroorganismslowsdown
(growthinhibitionphase),andinthenextstageitiscompletely
inhibited(stationaryphase).Duringthisperiodofgrowth,
thelargestamountofbiomassinthesystemisobserved.With
thelackofnutrientsandincreasingaccumulationoftoxic
metabolites,thecultureentersaphaseofdeathassociatedwith
adecreaseintheamountofbiomassinthesystem.Thegrowth
rateofthemicroorganismisdescribedbytheequation:
r
x
=µX
where:
r
µ-specificgrowthrate,
X-culturebiomasscontent.
x
-actualgrowthrate,
ThePfactor,alsocalledthespecificgrowthfactor,canbe
definedastheratioofthebiomassgrowthratetotheexisting
one.Mostoftenitsunitish
-1
.
Lag-phase
Acceleratongrowth
Logarithmic
Growthinhibiton
Statonary
Death
Growthphase
Specificgrowthrate
µ<µ
µ=µ
µ<µ
µ=0
µ=0
µ<0
max
max
max
Sincethegrowthofthemicroorganismintheexponential
phaseisatitshighestrate,thesubstrateiseasilyaccessibleand
theresultingmetabolitesdonotadverselyaffectthegrowth
(optimalconditionsprevail),thebiomassgrowthreachesits
highestvalueofP
max
.
35
Table103010Growth
ratedependingon
growthphase.