Enzyme Technology
Use of lytic methods
The breakage of cells using non-mechanical methods is
attractive in that it offers the prospects of releasing enzymes under conditions
that are gentle, do not subject the enzyme to heat or shear, may be very cheap,
and are quiet to the user. The methods that are available include osmotic shock,
freezing followed by thawing, cold shock, desiccation, enzymic lysis and
chemical lysis. Each method has its drawbacks but may be particularly useful
under certain specific circumstances.
Certain types of cell can be caused to lyse
by osmotic shock. This would be a cheap, gentle and convenient method of
releasing enzymes but has not apparently been used on a large scale. Some types
of cell may be caused to autolyse, in particular yeasts and Bacillus
species. Yeast invertase preparations employed in the industrial manufacture of
invert sugars are produced in this manner. Autolysis is a slow process compared
with mechanical methods, and microbial contamination is a potential hazard, but
it can be used on a very large scale if necessary. Where applicable, dessication
may be very useful in the preparation of enzymes on a large scale. The rate of
drying is very important in these cases, slow methods being preferred to rapid
ones like lyophilisation.
Enzymic lysis using added enzymes has been used widely
on the laboratory scale but is less popular for industrial purposes. Lysozyme,
from hen egg-white, is the only lytic enzyme available on a commercial scale. It
has often used to lyse Gram positive bacteria in an hour at about 50,000 U Kg−1
(dry weight). The chief objection to its use on a large scale is its cost. Where
costs are reduced by the use of the relatively inexpensive, lysozyme-rich, dried
egg white, a major separation problem may be introduced. Yeast-lytic enzymes
from Cytophaga species have been studied in some detail and other lytic
enzymes are under development. If significant markets for lytic enzymes are
identified, the scale of their production will increase and their cost is likely
to decrease.Lysis by acid, alkali, surfactants and solvents can be effective in
releasing enzymes, provided that the enzymes are sufficiently robust.
Detergents, such as Triton X-100, used alone or in combination with certain
chaotropic agents, such as guanidine HCl, are effective in releasing
membrane-bound enzymes. However, such materials are costly and may be difficult
to remove from the final product.
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This page was established in 2004 and last updated by Martin
Chaplin on
6 August, 2014
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