Optimization of the Fed-Batch Fermentation Process for Lysine Production

Author : Billena, Tessier Rey M.
Major Adviser : Chay, Pham Binh
Committee Members : Acda, Reynaldo I.; Movillon, Jovita L.
Year : 1992
Month : October
Type : Thesis
Degree: BS
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Abstract

The effect of glucose concentration on lysine production using a homoserine auxotroph Brevibacterium flavum BN 123 was determined using batch fermentation at an initial pH of 7.0 and agitation speed of 200 rpm. Maximum lysine yield was observed to be at 160 g/L initial sugar concentration. The effect of initial pH and agitation speed were then determined in a fed-batch fermentation process at a glucose concentration of 160 g/L. Maximum yield of lysine was obtained at an initial pH of 7.0 and agitation speed of 400 rpm. An equation to predict the lysine yield as function of agitation speed (X2) and feeding cycle time (X1) was developed.

Y =- 2.51+0.00575X1+0.035X2+4.32E-4X1²-4.28E-5X2² +1.55E-4X1X2

Through response surface analysis using the equation above, maximum predicted lysine yield is 6.64 g/L with feeding cycle time of 24 hours and agitation of 452 rpm.

With an initial pH of 7.0, agitation speed of 400 rpm and glucose concentration of 160 g/L, the effect of feeding cycle time on lysine production was also determined. The maximum lysine yield was obtained at a feeding cycle time of 24 hours. An equation was also developed to predict maximum lysine (Y3), biomass concentration (Y1) and residual sugar concentration (Y2) as a function of feeding cycle time (X2) and sampling time (X1). Their values were then determined at the critical or stationary point.

Y1 =- 2.15+0.16X1+1.17X2-0.0015X1²-0.035X2²+0.000825X1X2

Y2=129.24-3.56X1-0.76X2+0.031X1²-0.01187X2² +0.003X1X2

Y3=1.02+0.09X1+0.055X2-0.0009X1²-0.0022X2²+0.00269X1X2

Through response surface analysis and with the equations, maximum predicted lysine is 7.37 g/L at feeding cycle time of 124 hours at a sampling time of 72 hours. Critical residual sugar concentration and biomass concentration is 0.2711 g/L at a feeding cycle time of 28 hours and a sampling time of 57 hours and 12.64 g/L at a feeding cycle time of 17 hours and a sampling time of 56 hours, respectively.

Further experiments are necessary to test the interaction effects of glucose concentration, agitation speed, initial pH, and feeding cycle time.

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