Chemical Engineering March 2022 - 27

Technology Profile
Production of L-Lysine
By Intratec Solutions
L
ysine (Figure 1) is an α-amino
acid used in the biosynthesis
of proteins. The compound
contains an amino group and
a carboxylic acid group. Under biological
conditions, the amino group is
protonated (-NH3+) and the carboxylic
acid group is deprotonated (-COO-).
The α-carbon of lysine is a chiral
center, so two enantiomers of the
compound exist. Only L-lysine is biologically
active. Lysine is an essential
amino acid that must be supplied
through the diet. It is commercially
produced as L-lysine monohydrochloride
(L-lysine·HCl) and L-lysine sulfate.
L-lysine·HCl is a yellowish-white, crystalline
powder, mainly used as a food
and feed supplement. Other uses relate
to cosmetics, human medicine,
culture media and pharmaceuticals.
Lysine is produced from raw sugar
(sucrose) using a conventional
fermentation process in which raw
sugar is hydrolyzed into glucose and
fructose (invert sugars). The invert
sugars are then fermented to produce
L-lysine, which is recovered via
ion-exchange adsorption.
Process
Fermentation-based lysine production
from raw sugar is similar to the
Archer-Daniels-Midland process, and
Glucose syrup
Pathway A
Fermentation
L-Lysine-HCl
Cyclohexene
Pathway C
Chemical synthesis
Raw material(s)
Pathway
Product under analysis
Other product(s)
FIGURE 3. Several pathways for making L-lysine exist, including fermentation and chemical synthesis,
which is less common
comprises three major sections: (1)
fermentation; (2) product recovery;
and (3) product concentration, drying
and packaging (Figure 2).
Fermentation. The culture media
used in fermentation is prepared by
mixing process water, invert sugar
and nutrients. The fermentation is performed
in fed-batch mode and under
aerobic conditions. To start the batch
phase, the microorganism seed is fed
into the fermenters, which were previously
filled with the fermentation batch
medium. After glucose exhaustion, the
batch phase is finished and the fedbatch
phase is started, during which,
glucose and nutrients are continuously
supplied until the desired L-lysine concentration
is achieved. At the end of
the fermentation, the broth is sent to
a buffer tank to provide a continuous
flow in the further process steps.
Product
recovery.
The
fermentaFIGURE
1. L-lysine is an essential amino acid with
a chiral center
tion broth is sent to an ultrafiltration
system for the removal of cell debris
and other suspended solids. Subsequently,
the liquor from ultrafiltration is
fed to ion-exchange columns, where
L-lysine is selectively adsorbed. The
adsorbed L-lysine is then eluted from
the ion-exchange resins by washing
with an aqueous ammonia solution.
Product concentration, drying and
packaging. The L-lysine eluate from
ion exchange columns is mixed with
mother liquor from the product filtration
step and concentrated by evaporation.
The concentrated lysine solution
is acidified with hydrochloric acid,
and free L-lysine is converted to Llysine·HCl.
Subsequently, the L-lysine
·HCl solution is sent to the crystallizer,
and lysine salt is filtered. The mother
liquor is recycled to the evaporator
and the wet cake is conveyed to dryers.
Final dry L-lysine·HCl (98.5 wt.%)
is obtained and sent to packaging line
before being stored in bags. L-lysine
is hygroscopic, so it must be stored in
tightly sealed containers tightly in dry,
cool conditions.
Pathways and uses
The
L-lysine·HCl
process
involving
sugar fermentation is accomplished by
modified microorganisms. The sugar
used in the bio-based chemical route
can be derived from sugarcane, beet
or corn. L-lysine can also be produced
from cyclohexene via a chemical pathway.
However, only a few plants use
this alternative (Figure 3).
n
1. Sugar inversion
2. Medium vessels
3. Fermenters
4. Buffer tank
5. Ultrafiltration unit
6. Ion-exchange unit
7. Evaporator
8. Crystallizer
9. Product filter
10. Dryer
11. Chiller
12. Cooling tower
13. Steam boiler
CW Cooling water
ST Steam
CHW Chilled water
FIGURE 2. The diagram shows the production process for L-lysine
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
MARCH 2022
27
Editor's note: The content
for this column is developed
by Intratec Solutions
LLC (Houston; www.
intratec.us) and edited by
Chemical Engineering.
The analyses and models
presented are based on
publicly available and nonconfidential
information.
The content represents the
opinions of Intratec only.
Pathway B
Fermentation
Raw sugar

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Chemical Engineering March 2022

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