Biomedical Engineering Reference
In-Depth Information
comparable (70% and 80% respectively). Optimum economic conditions were established,
corresponding to average transmembrane pressures of 2.2 and 3.8 bars and tangential flow
velocity of 6.0 and 0.47 m/s for Ceraver and PCI membranes, respectively. The protein
concentration in the feed solution was increased from 5 to 35 g/dm
3
. The study showed that
the method could reduce pollution due to organic matter by decreasing the value of the
biological oxygen demand after 5 days (BOD5) by 80% (Mameri et al., 1999).
Collagen and gelatin are currently used in diverse fields including food, cosmetic, and
biomedical industries. Fish skin waste could be used as a potential source to isolate collagen
and gelatin. Kim and Byun (1994) designed a three-stepped membrane bioreactor for
continuous hydrolysis of fish skin gelatin. The system involved three hollow fiber
ultrafiltration membranes with molecular weight cut-off of 10 (first step), 5 (second step) and
1 (third step) kDa respectively. The enzymatic hydrolysates of gelatin extracted from fish skin
were fractionated and recycled through the membrane bioreactors. Alcalase, pronase E and
collagenase were identified as the most suitable enzymes for the hydrolysis of fish skin
gelatin. After optimization of operating conditions including temperature, pH, type of
enzyme, substrate to enzyme ratio, flow rate and reaction volume, the degree of hydrolysis
under the optimum condition in the first, second and third membrane bioreactor were 87%,
77% and 70% respectively. The productivity of hydrolysate in the continuous three-step
membrane bioreactor was 430 mg/mg enzyme. These hydrolysates could be not only used in
conventional ways as mentioned above, but also applied for production of functional peptides.
The fragments arising from the third step were composed of peptides ranging from 0.9 to 1.9
kDa and responsible for an inhibitory activity of angiotensin I converting enzyme. These
fragments have great potential application in medical science for regulation of blood pressure
(Byun and Kim, 2001).
Alvise et al. (2004) also obtained an antihypertensive peptide from an Alfalfa White
protein hydrolysate produced by a continuous enzymatic membrane bioreactor. Insoluble
alfalfa protein concentrate (APC) was solubilised by two proteolytic enzymes (pepsin and
delvolase) in batch and in continuously flowed membrane bioreactor. The main components
of the system included a 8 liter reaction vessel coupled with a membrane module via a
recirculation pump. The substrate (APC) was pretreated overnight at pH 2.0 and 40
o
C and
then preset to the required pH (9.5) in the feed vessel and pumped into the reaction vessel at
a flow rate equal to the permeate flux (16.6 dm
3
/m
2
.h). Temperature, pH and reaction volume
were continuously regulated. The membrane module was composed of seven tubular ZrO
2
membranes (6 mm inner diameter, 1.2 m length, 0.16 m
2
filtering area) with 10 kDa nominal
molecular weight cut-off. The optimum conditions of hydrolysis were found to be 2.4 mg/dm
3
of enzyme, 32 g/dm
3
of APC with a conversion rate of 75.9%. The ultrafiltration was
conducted through ZrO
2
membrane of 10 kDa with no significant loss of enzyme. This
membrane is approved for application in food industries. Flow rate of 2.22 cm
3
/min, reactor
volume of 400 cm
3
and resident time of 180 min appeared to be an optimum conditions for
ultrafiltration. This process provides a soluble peptidic product with a light brown color. High
conversion and complete rejection of the substrate and enzyme are promising. The peptide
obtained from this hydrolysis process has been proved to highly inhibit the activity of
angiotensin I converting enzyme (Kapel et al., 2006).
NovaTec (1994) provided a comparison between ultrafiltration and other methods for
recovery of protein and reduction of BOD from clam processing wastewater. Protein recovery
(%) were 60-70, 72, 79, 90, 90, 88 while BOD reduction (%) were 72, 62, 79, 91, 91, 87 for
