smooth, acoustically induced aggregation coupled with the increasing sedimentation
(Bosma et al. 2003). The idea is to use ultrasonic energy to start concentrating the
algae at a specific position or node to promote fast recovery. Ultrasonic separation
can be implemented continuously, cells remain viable (experiencing low amount of
stress), is free from fouling, has limited active parts that breakdown during the
operation, and space requirement is relatively low. However, this method was
considered less economical than centrifugation for commercial harvest of algal
cells mostly due to the cooling system necessity and concentration factor which is
relatively low paralleled to centrifugation and micro-filtering. It could be useful in a
system comprising of a metabolite secretion from alga, and extracting living cells for
reprocessing in the development of additional substance while collecting the metabolite from the media would be advantageous.
1.4 Cell Disruption Techniques
Usually, the composition of microalgal cell walls varies with different organisms
except for Euglena and Dunaliella, because they do not have a cell wall. Cell walls
consist of glycoproteins, cellulose, fat, xylan, uronic acid mannose, alganic fibers,
and minerals, for example, calcium or silicate. Application of microwave techniques,
sonic waves, pounding by bead, high temperature application by autoclave, size
reduction, shock with the help of osmosis, homogenization, freezing, dehydration,
and 10% (weight per volume) sodium chloride addition are numerous methods of
cell disruption (Amaro et al. 2011). Simple mechanical grinding is easy and quick
but the rise in temperature due to grinding will reduce certain compounds. Grinding
can also be achieved with liquid nitrogen, making the process comparatively simpler. Breaking the cells by application of direct physical force is one of the mechanical methods and benefits include that these methods can be applied
comprehensively irrespective of species to a biomass. Additionally, chances of the
target products being damaged or degenerated during cell disruption are very low.
Harrison (1991) offered various cell disruption options, such as high-pressure
homogenization, pounding through bead, and grinding through mortar and pestle
that belong to mechanical class, but there are limited significant methods.
1.4.1 Bead Beating
It is better known as beadmill or ballmill, is among the simplest techniques of
disruption of cell that split cells by filling target cells and beads made of quartz or
any other type of metal in a closed vessel and then application of shaking force.
Disturbance is caused by bead’s contact or frictional force which results in grinding.
Extracting DNA from biological samples is one of the most general applications of
bead mill (Robe et al. 2003). Bead beating could indeed destabilize a cell very
1 Downstream Processing of Biofuels
25
(Bosma et al. 2003). The idea is to use ultrasonic energy to start concentrating the
algae at a specific position or node to promote fast recovery. Ultrasonic separation
can be implemented continuously, cells remain viable (experiencing low amount of
stress), is free from fouling, has limited active parts that breakdown during the
operation, and space requirement is relatively low. However, this method was
considered less economical than centrifugation for commercial harvest of algal
cells mostly due to the cooling system necessity and concentration factor which is
relatively low paralleled to centrifugation and micro-filtering. It could be useful in a
system comprising of a metabolite secretion from alga, and extracting living cells for
reprocessing in the development of additional substance while collecting the metabolite from the media would be advantageous.
1.4 Cell Disruption Techniques
Usually, the composition of microalgal cell walls varies with different organisms
except for Euglena and Dunaliella, because they do not have a cell wall. Cell walls
consist of glycoproteins, cellulose, fat, xylan, uronic acid mannose, alganic fibers,
and minerals, for example, calcium or silicate. Application of microwave techniques,
sonic waves, pounding by bead, high temperature application by autoclave, size
reduction, shock with the help of osmosis, homogenization, freezing, dehydration,
and 10% (weight per volume) sodium chloride addition are numerous methods of
cell disruption (Amaro et al. 2011). Simple mechanical grinding is easy and quick
but the rise in temperature due to grinding will reduce certain compounds. Grinding
can also be achieved with liquid nitrogen, making the process comparatively simpler. Breaking the cells by application of direct physical force is one of the mechanical methods and benefits include that these methods can be applied
comprehensively irrespective of species to a biomass. Additionally, chances of the
target products being damaged or degenerated during cell disruption are very low.
Harrison (1991) offered various cell disruption options, such as high-pressure
homogenization, pounding through bead, and grinding through mortar and pestle
that belong to mechanical class, but there are limited significant methods.
1.4.1 Bead Beating
It is better known as beadmill or ballmill, is among the simplest techniques of
disruption of cell that split cells by filling target cells and beads made of quartz or
any other type of metal in a closed vessel and then application of shaking force.
Disturbance is caused by bead’s contact or frictional force which results in grinding.
Extracting DNA from biological samples is one of the most general applications of
bead mill (Robe et al. 2003). Bead beating could indeed destabilize a cell very
1 Downstream Processing of Biofuels
25