(12) PATENT (19) AUSTRALIAN PATENT OFFICE

(54) Title Membrane processes

(51) 6 International Patent Classification(s)

(21)

(30) (31)

(43) (43) (44)

BOlD 071/68 BOlD 071/06 BOlD 065/08 C02F 001/44

Application No: 199881964

Priority Data

Number 97/7805

(32) Date

Publication Date: Publication Journal Date· Accepted Journal Date.

1997.08.29

1999.03.18 1999.03.18 2000.12.21

(71) Applicant(s) Water Research Commission

(72) Inventor(s)

(11) Application No. AU 199881964 82 (10) Patent No. 727776

(22) Application Date 1998.08.28

(33) Country ZA

Kirsten Buchanan; Petrus Jacobs

Winston Daniel Leukes; Peter Dale Rose; Edmund

(74) Agent/Attorney FREEHILLS CARTER SMITH BEADLE,Level 43,101 Collins Street,MELBOURNE VIC 3000

(56) Related Art GB 1486305 WO 92/12241

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ABSTRACT

A membrane separation process for separating a contaminant from

a contaminated fluid includes passing the contaminated fluid through a

semi-permeable membrane on at least a portion of which an enzyme is

immobilized, so that a foulant layer which includes the contaminant forms

an the membrane in contact with the enzyme. The enzyme is capable of

being activated or induced to catalyse degradation of the foulant layer.

The process includes activating or inducing the enzyme thereby at least

partially to degrade the foulant layer .

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AUSTRALIA

Patents Act 1990

COMPLETE SPECIFICATION

Name of Applicant:

Actual Inventors:

Address for service in Australia:

Invention Title:

FOR A STANDARD PATENT

ORIGINAL

WATER RESEARCH COMMISSION

Kirsten BUCHANAN, Winston Daniel LEUKES. Peter Dale ROSE and Edmund PetlUs JACOBS

CARTER SMITH & BEADLE 2 Railway Parade Camberwell Victoria 3124 Australia

MEMBRANE PROCESSES

The follOWing statement is a full description of this invention, including the best method of peIfomUng it known to us

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THIS INVENTION relates to membrane processes. In particular, it

relates to a method of treating a semi-permeable membrane. to a treeted

semi-permeable membrane. and to a membrane separation process.

According to a first aspect of the invention, there is provided a

membrane separation process for separating a contaminant from a

contaminated fluid, the process including

passing the contaminated fluid through a semi-permeable membrane

on at least a portion of which an enzyme is immobilized so that a foulant

layer which includes the contaminant forms on the membrane in contact

with the enzyme, the enzyme being capable of being activated or induced

to catalY5e degradation of the foulant layer; and

activating or inducing the enzyme thereby at least partially to

degrade the foulant layer.

The contaminated fluid is typically an aqueous solution. Thus, it is

expected that the membrane separation process will find particular, though

not necessarily exclusive. application in the treatment of water. The

contamil1ated fluid may thus be contaminated water in need of purification,

e.g. river water.

Typically, the membrane has an upstream or filtration surface, The

enzyme may be immobilized on the upstream or filtration surface of the

membrane, the faurant layer thus forming on the enzyme-covered

upstream or filtration surface of the membrane.

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The foulant layer is typically depos'lts of organic polymers when the

process is employed to purify river water. However. as will be

appreciated. the nature of the foul ant layer depends an the contaminant

in the fluid.

The enzyme may be selected from the group consisting of

manganese peroxidase. activatable amylases. activatable proteases. and

two or more thereof. When two or more enzymes are used, they would

typically be in the form of a mixture. However, it is to be appreciated that

this is not a comprehensive list of enzymes, and that a particular enzyme

may be selected depending on the purpose for which the membrane is

intended.

Activation or induction of the enzyme may be by any suitable

method known to those skilled in the art. such as contacting the enzyme

with an activator solution. Thus. in principle the separation process can

be continuous, with the activator solution being injected into the

contaminated fluid at intermittent or regular intervals.

In one embodiment of the invention the enzyme is an extract of

manganese peroxidase produced by the white rot fungus Phanerochaete

chrysospor(um and activating the enzyme includes passing a solution of

hydrogen peroxide and manganese sulphate through the membrane.

The method may include inhibiting or deactivating the enzyme after

the foulant layer has been at least partially degraded, if necessary,

whereafter more fluid may be passed through the membrane. Inhibiting or

deactivation of the membrane may be by washing the activator solution

from the membrane. It is thus expected that the membrane may be used

repeatedly before the catalytic activity of the enzyme is reduced to an

ineffective level. Once the enzyme catalytic activity is reduced to an

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ineffective level, the enzyme may be removed from the membrane and

fresh enzyme may b'e immobilized on the membrane.

The catalytic activity of the enzyme can be considered to be

reduced to an ineffective level if an inadequate improvement in flux of the

fluid through the membrane is noticed upon activation of the enzyme. If

it is suspected that the enzyme is still active, but that some other factor

is preventing flux restoration on activation of the enzyme, an indicator can

be used to confirm this suspicion. A typical indicator would be an enzyme

substrate which is not retained by the membrane or the foulen! layer, and

which may be added to the activator solution.

The membrane may be a polysulphone membrane such as a

membrane supplied by the University of Stellenbosch and having a 30000

MWCO.

According to a second aspect of the invention, there is provided a

method of treating a semi-permeable membrane, the method including

immobilizing an inducible or activatable enzyme on at least a portion of the

membrane to produce a treated or modified membrane .

The enzyme may be immobilized on at least a portion of a surface

of the membrane. Typically, the surface of the membrane on which the

enzyme Is Immobilized is a filtration surface which in use is an upstream

surface or active filtration surface of a membrane employed in an

ultrafiltration process, a nanofiltratlon process, a microfiltration process,

a reverse osmosis process or the like process.

Preferably, the enzyme is immobilized on the entire filtration surface

of the membrane, as evenly as possible.

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The immobilization of the en~yme on the surface of the membrane

may be effected by contacting the surface of the membrane with a

solution of the enzyme, and a1\owing the enzyme to adsorb onto the

surface. Contacting the surface of the membrane with the solution of the

enzyme may be effected by passing the solution through and/or across the

membrane.

Instead, or in addition, immobilizing the enzyme may include

absorbing the enzyme into pores of the membrane.

The method may include inhibiting or deactivating the enzyme

before it is immobilized on the membrane, thereby selectively to reduce the

enzyme's catalytic activity towards a particular material. Instead, the

method may include inhibiting or deactivating the enzyme after it has been

immobilized on the membrane, thereby selectively to reduce the enzyme's

catalytic activity towards a particular material.

Inhibiting of the enzyme may be by any suitable method known to

those skilled in the art. such as contacting the enzyme with a competitive

or non-competitive inhibitor.

The enzyme may be as hereinbefore described.

Accordin~ to a third aspect of the invention. there is provided a

treated semi-permeable membrane an at least a portion of which an

activatable or inducible enzyme is immobilized.

The immobilized enzyme may be in the form of a layer on a surface

of the membrane. Preferably. the immobilized enzyme is in the form of a

layer covering an entire major surface of the membrane, as evenly as

possible.

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An optimum thickness of ~he layer may be determined by

experimentation by those skilled in the art, and factors which would

determine the optimum thickness of the layer include the catalytic activity

of the enzyme, the nature of the enzyme and the purpose far which the

treated membrane is intended. However, the layer thickness (ie the

concentration of the enzyme on the membrane) should allow a process in

which the enzyme takes part catalytically to proceed at a COSt effective

and time efficient rate. Thus, in one embodiment of the invention. the

Applicant has found a layer of manganese peroxidase having a

concentration of 0,016U/cm' to give an adequate performance, and a layer

of manganese peroxidase having a concentration of 0, 16U/cm' giving a

good performance.

Instead, or in addition, the immobilized enzyme may be present in

pares of the membrane .

The enzyme may be as hereinbefore described.

The invention is now described, by way of example, with reference

to the accompanying Example, Figure 1 which is a schematic diagram of

an ultrafiltration cell system and Figures 2 - 4 which are graphs of

experimental results obtained with the ultrafiltration cell system af Figure

1 .

Referring to Figure 1. reference numeral 10 generally indicates an

ultrafiltration cell system.

The system 10 includes a nitrogen cylinder 14 and an ultrafiltration

cell 16. A nitrogen flow line 18 leads from the nitrogen cylinder 14 to the

ultrafiltration cell 16. A pressure gauge 20 and an inducer port 22 are

provided in the nitrogen flow line 18.

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The ultrafiltration cell 16 includes a pressure release valve 24 and

an internal stirrer bar 26. A membrane 12 which, in the Examples below,

was used in an untreated state or was pre-treated with an enzyme

according to the method of the invention, is located below the stirrer bar

26. The membrane has a diameter of about 62mm, The ultrafiltration cell

16 is mounted on a magnetic stirrer 28. A permeate flow line 30 leads

from the ultrafiltration cell 16 into a permeate collector 32.

The membrane 12 before treatment is a polysulphone flat membrane

having a 30000 MWCO, provided by the University of Stellenbosch, and

is a standard type ultrafiltration membrane .

The ultrafiltration cell system 10 was used to conduct fOlJr

ultrafiltration experiments during which the flux of water through the

treated or untreated membrane 12 as a function of time was determined.

In each experiment, the treated or untreated membrane 12 was installed

inside the ultrafiltration call 16, and the cell 16 was filled with riller water.

Nitrogen from the nitrogen cylinder 14 was fed to the ultrafiltration Gell 16

by means of the nitrogen flow line 16, to force the water under a pressure

of 160kPa through the membrane 1 2, while the water was stirred. The

volume of permeate collected in the permeate collector 32 was measured

as a function of time and the flux of the water through the membrane 12

was calculated as a function of time.

EXAMPLE 1

In a first experiment, river water was passed through the untreated

membrane 12. The results of the experiment are S9t out in the graph in

Figure 2, which shows the decline of the flux of the rilier water passing

through the membrane 12 as a function of time, and in Table 1 under

Example 1 (al. The experiment was repeated, but this time a chemical

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activator solution comprising hydrogen peroxide and manganese sulphate

(Smel having a H20, concentration of 0,05 % Iv/Viand a MnSO •. 7H,O

concentration of O,475mg/ml was injected into the ultrafiltration cell 16

by means of the inducer port 22. The activator solution was injected after

, 5 minutes and again after about 33 minutes from the start of the

experiment. The results ara set out in Table 1 under Example lib).

EXAMPLE 2

A second experiment was conducted in which a crude extract of

manganese peroxidase 15mll, produced by the white rot fungus,

Phanerochaete chrysosporium, having a concentration of the enzyme of

approximately Q.SU/m£ Iwhere 1 U = 100 pmol of substrate utilized in 1

minute, with the substrate being 2,2" azino-dH3-alkyl-benzthiazolin­

sulfonateI6)1I, was passed through the membrane so that the enzyme was

immobilized on the membrane 12 by adsorption. River water was passed

under pressure through the treated membrane 12 as described above and

the flux of the river water was measured as a function of time. The

results of the experiment are set out in Graph 1 in Figure 3 which shows

the decline of the flux as a function of time and in Table 1.

EXAMPLE 3

A third experiment was conducted in which a membrane 12 treated

with a crude extract of manganese peroxidase produced by the white rot

fungus Phanerochaete chrysospor;um, as described in Example 2 above,

was used. River water was again passed through the membrane 12 under

pressure as described above and the flux of the river water as a function

of time was measured. However, in this experiment, the enzyme was

induced or activated by injecting the same chemical activator solution as

described in Example 1. The activator solution was injected after 15

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minutes and again after about 33 minutes from the start of the

experiment. The results of the experiment are set out in Graph 2 in Figure

3, which shows the effect of the induction or activation of the enzyme on

the flux of the river water as a function of time, and under Example 318)

in the Table. The experiment was repealed and the results are set out

under Example 31b) in the Table.

EXAMPLE 4

A fourth experiment was conducted, in which a membrane 12 on

which a denatured man9ane~e peroxidase enzyme was adsorbed, was

used. The enzyme was immobilized on the membrane 12 in the same

fashion as in Example 3, after the enzyme was denatured by boiling it .

The flux of the river water was again measured as a function of time, and

the activator solution, as described in Example 3. was injected into the

·ultrafiltration cell 16 after 15 minutes and again after about 35 minutes.

The results of the experiment are set out in the graph in Figure 4 which

shows the flux of the river water as a function of time.

Table 1 tabulates some of the flux measurements as a function of

time far the experiments described in the Examples abOVE!.

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TABLE 1

Example 1 Example 2 Example 3 Example 4 la) (b) ral Ibl

Initial flux 730,8 610,84 211,6 213,79 231,24 381,78

l~r15 100.35 106,BO 95,99 98,17 109,08 113,44

Flux after 17 95,99 107,98 95,99 135.26 119.98 113.44 minutes

Flux after 22 87.26 95,99 87.26 104.71 117.8 102.54 minutes .

Flux at end 34.9 52.35 78,35 87,26 75.27 63.26 of experiment

As can be seen from Figure 3. there is an improvement in the flux

of the river water through the membrane 12 after induction or activation

of the enzyme with the chemical activator solution, Experiment 4 was a

control for the third experiment. and shows that induction of the denatured

enzyme does not affect the flux of the water through the membrane as did

induction of the enzyme in Experiment 3,

It is an advantage of the membrane separation process, as

illustrated. that the enzyme is inhibited when immobilized an the

membrane when its catalytic activity is not required and can therefore be

re-used several times before being replaced. It is also an advantage of the

separation method as illustrated. that no toxic chemicals are needed for

cleaning the membrane, and that no processes which can lead to damage

to the membrane. for example by using aggressive chemicals. afe

emploved to clean the membrane, It is vet a further advantage of the

membrane separation process, as illustrated. that the chemical activator

does not need neutralisation, since it is simply flushed from the membrane

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after induction of the enzyme. The invention thus effectively provides a

self-cleaning membrane for use in ultrafiltration and similar processes .

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THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A membrane separation process for separating a contaminant from

a contaminated fluid, the process including

passing the contaminated fluid through a semi-permeable membrane

on at least a portion of which an enzyme is immobilized so that a foulant

layer which includes the contaminant forms on the membrane in contact

with the enzyme. the enzyme being capable of being activated or induced

to catalyse degradation of the foulant layer; and

activating or inducing the enzyme thereby at least partially to

degrade. the foulant layer .

2 . A process as claimed in claim 1, in which the enzyme is immobilized

on an upstream or filtration surface of the membrane, the foulant layer

thus forming on the enzyme-covered upstream or filtration surface of the

membrane .

3. A process as claimed in claim 1 pr claim 2, in which the enzyme is

selected from the group consisting of manganese peroxidase, activatable

amylases, activatable proteases, and two or more thereof.

4. A process as claimed in anyone of the preceding claims, in which

activating or inducing the enzyme includes contacting the enzyme with an

activator solution.

5. A process as claimed in claim 4, which is a continuous process

wherein contacting the enzyme with the activator solution comprises

injecting the activator solution into the contaminated fluid at intermittent

or regular intervals.

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6. A process as claimed in claim 4 or claim 5. in which the enzyme is

an extract of manganese peroxidase and the activating solution is an

aqueous solution of hydrogen peroxide and manganese sulphate.

7. A process as claimed in anyone of the preceding claims. which

includes inhibiting or deactivating the enzyme after the foulant layer has

been at least partially degraded.

8. A process as claimed in anyone of the preceding claims. in which

the membrane is a polysulphone membrane .

9. A process as claimed in anyone of the preceding claims. in which

the contaminated fluid is contaminated water in need of purification .

10. A method of treating a semi-permeable membrane, the method

including immobilizing an irlducible or activatable enzyme on at least a

portion of the membrane to produce a treated or modified membrane .

11. A method as claimed in claim 10. in which the enzyme is

immobilized on at least a portion of a surface of the membrane.

12. A method as claimed in claim 11, in which the surface of the

membrane is a filtration surface. and wherein the enzyme is immobilized

on the entire filtration surface of the membrane.

13. A method as claimed in claim 11 or claim 12. in which the

irnmobili~ation of the enzyme on the surface of the membrane is effected

by contacting the surface of the membrane with a solution of the enzyme.

and allowing the enlym. to adsorb onto the surface.

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14. A method as claimed in any ol1e of claims 10 to 13 inclusive, in

which immobilizing the enzyme includes absorbing the enzyme into pores

of the membrane.

15. A method as claimed in anyone of claims 10 to 14 il1clusive, which

includes inhibiting. or deactivating the enzyme before it is immobilized on

the membrane, thereby selectively to reduce the enzyme's catalytic

activity towards a' particular material.

16. A method as claimed in anyone of claims 10 to 14lncluslv9, which

Includes inhibiting 'or deactivating the enzyme after it has been immobilized

on the membrane, thereby selectively to reduce the enzyme's catalytic

activity towards a particular material.

17. A method as claimed in anyone of claims 10 to 16 inclusive, in

which the enzyme is selected from the group consisting of manganese

peroxidase. activatable amylases, activatable proteases. and two or more

thereof.

18. A treated semi-permeable membrane on at least a portiorl of which

an activatable or irducible enzyme is immobilized.

19. A membrarle as claimed in claim 18, in which the immobilized

enzyme is in the form of a layer covering an entire major surface of the

membrane.

20. A membrane as claimed in claim 18 or claim 19. in which the

immobilized enzyme is present in pores of the membrane.

21. A membrane as claimed in anyone of claims 18 to 20 'Irlclus'lve, in

which the enzyme is selected from the group consisting of marlganese

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peroxidase, activatable amylases, activatable proteases, and two or more thereof.

22. A membrane separation process as claimed in claim I, substantially as

hereinbefore described and illustrated.

23. A method of treating of semi-permeable membrane as claimed in claim 10,

substantially as hereinbefore described and illustrated.

24. A treated semi-permeable membrane as claimed in claim 18, as substantially

10 as hereinbefore described and illustrated.

15

DATED: 19 October 2000

FREEHILLS CARTER SMITH & BEADLE

Patent Attorneys for the Applicant:

WATER RESEARCH COMMISSION

19 October 2000

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