Biomedical Engineering Reference
In-Depth Information
direct acid precipitation, ion-exchange chromatography, single ultrafiltration, ion-exchange
chromatography combining with acid precipitation, ultrafiltration combining with acid
precipitation and microgas dispersion with flotation respectively. Membrane separation
showed its great competitive capacity comparing to other methods.
Except protein separation, enzyme separation is another important and valuable
application of ultrafiltration. DeWitt and Morrissey (2002) designed a ultrafiltration pilot
plant with membrane molecular weight cut-off 30 and 50 kDa for recovery of catheptic
proteases from fish mince washing water. Pretreatment of fish mince washing water by
heating at 60
o
C, acidification to pH 6, and centrifugation could double ultrafiltration flux and
significantly improved protease purity by reducing a majority of the 35-205 kDa proteins.
Concentrated crude protease obtained from washing water predominantly contained cathepsin
L activity. Enzyme purity was increased about 100-fold, and yield was approximately 80%.
Stability (frozen and freeze-dried protease) was maintained for 9 weeks at -80
o
C. Freeze-
dried preparations were also stable for 9 weeks at 4 and -15
o
C. Successful application of pilot
plant conditions allows sufficient production of protease for further investigations into their
applicability.
Gildberg and Shi (1994) recovered enzyme from fish sauce. A concentrate of tryptic
enzymes was obtained by ultrafiltration of fish sauce made from Cod's viscera. The recovery
of enzyme activity during ultrafiltration was good (> 80%). It showed that polysulphone
membranes can be successfully applied in ultrafiltration even at very high salt concentrations
(20-25%). The enzyme concentrate could be stored for 8 months at 3°C or spray dried with
only minor activity loss. In addition, nomudfish sauce fermentation was achieved after re-
addition of the ultrafiltration permeate to the fish sauce fermentation tank.
Li (2008) applied ultrafiltration to recover protease from yellowfin tuna spleen. After
extraction process and pretreatment by microfiltration membrane (Li et al., 2008),
ultrafiltration with a hollow fiber membrane (molecular weight cut-off 30 kDa) could separate
and purify trypsin and chymotrypsin from this spleen extract. Through a diafiltration mode
these protease was purified up to 12-fold. The purified enzyme was a clear solution without
odor. The activity of these protease was compared with some commercial enzymes, such as
alcalase. The enzymes separated from tuna spleen by ultrafiltion showed competitive
cabability of protein hydrolysis. The result showed that a trypsin-like serine protease with
low-cost and qualified hydrolysis efficiency could be obtained from tuna canning waste by
membrane technology involving microfiltration (pretreatment step) and ultrafiltration
(separation and purification steps).
Outer skeleton of crabs, shrimps and lobsters is also a waste from seafood processing.
Since it contains abundant chitin, a kind of polysaccharide, this waste has been utilized for
production of chitosan which is derived from chitin by deacetylation. Chitosan and its
derivatives have shown various functional properties and made them possible to be used in
many fields including food, cosmetics, biomedicine, agriculture, environmental protection
and wastewater management (Kim and Rajapakse, 2005). Even though chitosan is known to
have important functional activities, its poor solubility makes it difficult to use. Recent
studies on chitin and chitosan have attracted interest to convert them to
chitooligosaccharides, because the chitooligosaccharides are not only water-soluble but also
functionally versatile. To increase the solubility of chitosan in an aqueous solution and to
facilitate its utilization, the enzymatic production of chitooligosaccharides with a high degree
of polymerization (DP) was carried out using an ultrafiltration membrane bioreactor system.
