Kinetics of Microbial Growth Factors Determining Growth

1 Dr. Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ of Microbial GrowthUnlimited growthAssumingtd= h,in 48 h, one cell would X 1043cellsIf a cell weighs 10-12 g, then the total would be X 1031 gThis would be 4000 times the weight of the earth!Dr. Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ Determining Growth & Synthesis of Products Absolute FactorsNutrients; pH; Temperature; Oxygen Rate- Determining FactorsTemperature; pH; Mass Transfer; Energy TransferDr. Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ of Batch CultureGrowth Rate,rx= xtor as tbecomes infinitesimally small= cells mL-1h-1 Specific Growth Rate, = g-1 cells mL-1h-1Dr.

2 Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ Population SizeSpecific Growth Rate TimeLagAccelerationExponentialDecelerati onMaximumpopulationDeath maxLn Population SizeSpecific Growth Rate TimeLagAccelerationExponentialDecelerati onMaximumpopulationDeathLn Population SizeSpecific Growth Rate Ln Population SizeSpecific Growth Rate TimeLagAccelerationExponentialDecelerati onMaximumpopulationDeath maxKinetics of Batch Culture 2 Phases of Growth in batch cultureDr. Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ of Batch Culture 3 The exponential phase may be described bydxdtx= ( )wherex=[ Microbial biomass]t=time (h) =specific Growth rate (h-1)1471013160200040006000800010000 Cell NumberExponentialPhaseTimeDr.

3 Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ of Batch Culture 4 Integrating equation givesxt= x0e t( )wherexo=[original biomass]xt= [biomass after time t]e= base of natural logTaking natural log, equation becomeslnxt = lnx0+ tThus, plot of ln line in the exponential phase, slope of which = 14710131610100100010000 ExponentialPhaseLogCell NumberTimeDr. Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ dataTime(h)X(g L-1)S(g L-1) Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ data 2 Growth Rate, tangentryxx= differentiationDifference between values on either side of data pointrxxttx23131= fitting[]rxxttxx231312= lnlnDr.

4 Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ RateSubstrate concentration maxSpecificGrowth RateSubstrate concentration maxDetermining from dataUsing the values for Growth determined as described previously,Specific Growth Rate may be estimated by the relationshipxrx= However, in batch culture, does not remain concentration is a major affecting Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ max from data1. By tabulation of values for through the exponential phase of the (h)x(g L-1)rx(h-1)* = *rxvia numerical Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ maxfrom data plotSKSxrSKxSdtdxrsmmxsx+ =+ ==Taking the reciprocal and since =xrxmmmmmSKSSSKSSK rxsssx + = + = += = 1111Dr.

5 Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ maxfrom data 3 Compare111 = +KSsmmwithy = mx + cThus, when1 is plotted against 1S, we get 1 1 SSlope=Ks maxNote large number ofpoints in this areaIntercept=1 maxDr. Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ factorYY= the ratio of product or cell quantity resulting from a certain quantity of of cell weight per unit weight substrate utilizedYp/nYield of product weight per unit weight of nitrogen utilizedDetermination of Yield Factor on carbon substrate, Yx/srrYmxrxYrxmssssxsxsxs=+= +1wherers= rate of consumption of carbon substratems= maintenance coefficient on carbon substrateDr.

6 Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ of Yield Factor on carbon substrate, Yx/s 2 Thus, whenrxs is plotted against rxx , we getrxrxSlope=1Yx/sNote large number ofpoints in this areaIntercept = msDr. Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ Importance of maxFor processes where maximal Growth rates arediserable, attainment of maxin culture is maxis determined by the genetics of the microorganism conditions of cultureAttainment of maxhas implications for both other processes, identification of max is important so that it can be avoided the production of secondary Clem Kuek ZIP/Lect+Prac/IndusMicrobiol/ Importance of the Yield FactorYY indicates the degree of efficiency of the conversion of substrates into desired of efficient Y translates directly into economic efficiency, and thus is determined by the genetics of the microorganism conditions of culture nature of the input (substrate)Attainment of an efficient Yhas implications for the determinants.