Biomedical Engineering Reference
In-Depth Information
The chitosanase was used for enzymatic hydrolysis of chitosan and
able to be repeatedly
reused and separated from the final products (Jeon and Kim, 2000a). The system consisted of
a supplement tank, a reservoir tank, a water bath for controlling reaction temperature, three
peristaltic pumps, a membrane cartridge with molecular weight cut-off 3 kDa and an enzyme
reactor vessel. The most important factor in the ultrafiltration bioreactor system was a
permeation rate control because the components of the chitooligosaccharides were dependent
on the permeation rate. At a permeation rate of 4 ml/min, 80% of produced
chitooligosaccharides had 3-6 of DP.
However, ultrafiltration membrane method did not allow continuous production of
chitooligosaccharides due to the increased transmembrane pressure during the reaction. This
was due to high viscosity of chitosan solution and fouling of membrane by accumulated
substrate. Continuous production of chitooligosaccharides was achieved by a combination of
a column reactor packed with immobilized enzyme and the ultrafiltration membrane reactor,
namely dual membrane reactor system (Jeon and Kim, 2000b). The production of the
chitooligosaccharides was performed by two steps. The first step is the preparation of the
partially hydrolyzed chitosan from viscous chitosan in the column reactor packed with an
enzyme. The second step is the production of the chitooligosaccharides from partially
hydrolyzed chitosan in the ultrafiltration membrane bioreactor. Partially hydrolyzed chitosan
possessed low viscosity, leading to a decrease in membrane fouling. This dual membrane
reactor showed a greater productivity, ability to control molecular weight distribution and
more efficient continuous production process than those of conventional methods (Kim and
Rajapakse, 2005).
In addition to the treatment of wastes, membrane technology also shows its potential for
product promotion in fishery industry. Ultrafiltration was applied for fractionation of Cod
frame protein hydrolysate to improve its functional property (Jeon et al., 1999).
Since ultrafiltration membranes are capable of removing suspended solids and colloids,
viruses, bacteria, and high-molecular suspended organic material from the water. This
technology is very suitable for wastewater treatment or the pretreatment of surface water for
reverse osmosis, recycling of backwash from sand filters and recycling of seafood processing
and municipal wastewater. (Rosherg, 1997). Ultrafiltratiton can only be used as a
pretreatment provided that it is economically feasible.
An innovative membrane-assisted hybrid bioreactor for wastewater treatment in a fish
canning factory was developed by Artiga et al. (2005). This system was composed of a hybrid
circulating bed reactor and an ultrafiltration membrane module. The aerobic reactor was
coupled with an external submerged hollow-fiber ultrafiltration membrane module (average
pore size of 0.045 μm, nominal surface area of 0.093 m
2
). The operating transmembrane
pressure was in the range of 10-50 kPa. The result showed that the combination of a hybrid
system with suspended and attached biomass, and an ultrafiltration membrane module may
be an alternative for treating industrial wastewaters in compact biological systems with very
low footprint requirements. It has been shown that the system can operate simultaneously
with high COD and ammonia conversion rates at high nitrogen loading rate and organic
loading rate. COD removals around 99% at an organic loading rate of 6.5 kg COD/m
3
.d and
nitrogen loading rate of 1.8 kg N-NH
+
4
/m
3
.d were obtained during the treatment of the fish
canning wastewater.
Oyanedel et al. (2003) also tested a membrane-assisted hybrid bioreactor with similar
membrane to treat a mixture of two streams produced in a fish canning factory. This
