Claims:1. A formulation for controlling algal pests comprising at least one constituent which is at least one quaternary amine.

2. The formulation of claim 1 which includes at least one cationic polybiguanide.

3. The formulation of claim 2 which comprises a homogeneous mixture of at least one quaternary amine and at least one cationic polybiguanide.

4. The formulation as claimed in claim 1, wherein said quaternary amine is at least one selected from the group consisting of benzalkonium chloride, cetrimide, domiphen bromide and cetylpyridinium chloride.

5. The formulation as claimed in claim 1, wherein said cationic polybiguanide is dichlorohexidine gluconate.

6. A method for controlling the growth of a pest selectively in an aquatic environment, said method comprising contacting said pest with a pre-determined amount of the formulation claimed in any one of claims 1 to 5 without affecting the growth of algae.

7. The method as claimed in claim 6, wherein said pest is at least one selected from the group consisting of diatoms, flagellates, filamentous and unicellular cyanobacteria rotifers, ciliates and fungi.

8. The method as claimed in claim 4, wherein said aquatic environment is at least one of fresh water and sea water. , Description:FIELD
The present disclosure relates to controlling algal pests.
DEFINITION
As used in the present disclosure, the following term is generally intended to have the meaning as set forth below, except to the extent that the context in which it is used indicate otherwise.
Pests: The term “pests” refers to unwanted biological, microbiological and organic contaminants that interfere with the algal production.
BACKGROUND
There are several challenges to successfully use for algae as economically viable alternative to fossil fuels. The major challenge is continuous production of large quantities of algal biomass at a very low cost. To achieve this algae have to be stably cultivated round the year in open ponds at a sufficiently high density. However, algae cultivated in the open ponds are prone to numerous abiotic and biotic stresses, which lead to frequent culture crashes and productivity losses. Abiotic stress can be taken care to a large extent through bio prospecting, screening and selection of right kind of algal strains for a particular geographic location and season. Managing contaminants in open ponds along with maintaining high productivity of algae for successful biofuel production is very difficult. The technologies used to manage competition or predation in open ponds have proved to be unsuccessful as these methods limit the desired productivity, are incompatible for prospective candidate algal strains ideal for fuel production, are unable to act against wide variety of zooplanktons and are economically unviable.
Therefore, there is felt the need for a method for selectively controlling the algal pests during the production of algae.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to provide a method for controlling the algal pests.
Another object of the present disclosure is to provide a method for controlling algal pests in an aquatic environment.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure in an aspect provides a formulation for controlling algal pests comprising at least one constituent which is at least one quaternary amine. In another aspect, the formulation includes at least one cationic polybiguanide. Typically, the formulation comprises a homogeneous mixture of at least one quaternary amine and at least one cationic polybiguanide.
In another aspect a method for controlling the growth of a pest selectively in an aquatic environment, is provided. The method comprises contacting the pest with a pre-determined amount of a formulation comprising at least one constituent which is at least one quaternary amine and typically homogeneous mixture of at least one quaternary amine and a cationic polybiguanide, without affecting the growth of algae.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The disclosure will now be described with reference to the accompanying non-limiting drawing, wherein:
Figure 1A illustrates the effect of addition of different concentrations of benzalkonium chloride on the growth of Chlorella vulgaris;
Figure 1B illustrates the effect of addition of different concentrations of benzalkonium chloride on the growth of Chlorella vulgaris till 48 hours;
Figure 2A illustrates the effect of addition of different concentrations of benzalkonium chloride on the growth of Chlorella sorokiniana;
Figure 2B illustrates the effect of addition of different concentrations of benzalkonium chloride on the growth of Chlorella sorokiniana till 48 hours;
Figures 3A & 4A illustrate the effect of addition of different concentrations of benzalkonium chloride on the growth of Nannochloropsis;
Figures 3B & 4B illustrate the effect of addition of different concentrations of benzalkonium chloride on the growth of Nannochloropsis till 48 hours;
Figure 5A illustrates the effect of addition of different concentrations benzalkonium chloride on the growth of Picochlorum;
Figure 5B illustrates the effect of addition of different concentrations benzalkonium chloride on the growth of Picochlorum till 48 hours;
Figure 6A illustrates the effect of addition of different concentrations benzalkonium chloride on the growth of Cyanobacterium aponinum; and
Figure 6B illustrates the effect of addition of different concentrations benzalkonium chloride on the growth of Cyanobacterium aponinum till 48 hours.
DETAILED DESCRIPTION
Algae fuel or algal biofuel is an alternative to liquid fossil fuels that uses algae as its source of energy-rich oils. Use of algae as an alternative to the conventional fossil fuels requires large scale production of the algae. However, controlling contaminants in open ponds along with maintaining high productivity of algae for successful biofuel production is very difficult. The technologies used to manage competition or predation in open ponds have proved to be unsuccessful as these methods limit the desired productivity, are incompatible for prospective candidate algal strains ideal for fuel production, are unable to act against wide variety of zooplanktons and are economically unviable.
Accordingly, the present disclosure envisages a method for selectively controlling algal pests in an aquatic environment and thereby enhancing the growth of the algal production.
The present disclosure in an aspect provides a formulation for controlling algal pests comprising at least one constituent which is at least one quaternary amine. In another aspect, the formulation includes at least one cationic polybiguanide. Typically, the formulation comprises a homogeneous mixture of at least one quaternary amine and at least one cationic polybiguanide.
In another aspect a method for controlling the growth of a pest selectively in an aquatic environment, is provided. The method comprises contacting the pest with a pre-determined amount of a formulation comprising at least one constituent which is at least one quaternary amine and typically homogeneous mixture of at least one quaternary amine and a cationic polybiguanide, without affecting the growth of algae.
In accordance with the embodiments of the present disclosure, the quaternary amine is at least one selected from the group consisting of benzalkonium chloride, cetrimide, domiphen bromide and cetylpyridinium chloride.
In an embodiment of the present disclosure, the cationic polybiguanide can be Chlohexidine digluconate (CHG).
The formulation is affective against a broad range of zooplanktons encountered during open pond cultivation of algae, such as, ciliates, dinoflagellates, rotifers, protozoans, parasites, flagellates, fungi, bacteria, and the like, and is effective in low doses and acts quickly within a short residence time. The formulation of the present disclosure controls the pests by damaging the cell membrane of the pests, resulting in cell lysis and death of the pests. However, exposure to the formulation did not have any detrimental impact on the growth of algae strains, with only 10 % to 20 % growth inhibition reported for some strains at lethal dose that kill 100 % predators. In an embodiment of the present disclosure, the effective amount of the formulation is in the range of 0.5 ppm to 10 ppm. In another embodiment, the formulation is effective within 12 hours to 24 hours of residence time.
In an embodiment of the present disclosure, for maximum efficacy, the formulation is added during evening time and then the ponds are harvested /diluted after 12 hours to 24 hours. Since, QUAT’s are known to be degraded in the presence of oxygen, the formulation is added during the evening time. During day time the dissolved oxygen (DO) in ponds is high due to active photosynthesis and hence higher degradation of QUAT’s is observed as compared to the evening time, when the DO is much less.
The formulation is also effective in controlling diatoms, flagellates, filamentous and unicellular cyanobacteria when these are present in up to 10 % to 20% of the pond population.
The formulation is affective over a wide pH (4.0- 9.0) alkalinity (100 ppm to 500 ppm) and salinity (0.5 % to 6 %) range, making it effective both in marine (sea water) and fresh water algal cultivation systems. The formulation is also stable at high temperature.
The formulation does not persist in pond samples as they are rapidly taken up by the pests.
In another aspect of the present disclosure, there is provided a method for controlling the growth of a pest selectively in an aquatic environment. The method comprises contacting the pest with a pre-determined amount of a formulation described above and particularly comprising a homogeneous mixture of at least one quaternary amine and a cationic polybiguanide, without affecting the growth of algae. In accordance with the embodiments of the preset disclosure the pest is at least one selected from the group consisting of diatoms, flagellates, filamentous and unicellular cyanobacteria rotifers, ciliates and fungi. Use of a semi-turbid stat mode pond cultivation system, with daily harvesting and subsequent dilution with fresh water/media, results in the elimination of the formulation from the cultivation system. Further, the formulation is inexpensive and can be easily procured in in bulk amounts.
Table-1 summarizes the sensitivity of algal strains to different quaternary amines and formulations comprising quaternary amines with dichlohexidine gluconate (CHG).

Table-1
S.No. Formulation LD50 of algal strains after 48 hours exposure to different QUAT’s formulations (ppm)
C. sorokiniana
C. vulgaris
Nannochloris sp.
Picochlorum sp.
Nannochloropsis sp.
C. aponinum

1. Benzalkonium chloride (BAC) 10 10 7 25 10 2
2. Benzethonium chloride (BTC) 10 25 10 25 10 5
3. ATAB (cetrimide) 10 5 10 25 10 2
4. Domiphen bromide (DB) 25 25 25 50 10 10
5. Cetylpyridinium chloride (CPC) 5 5 10 10 5 2
6. Dichlorohexidine gluconate (CHG) 5 10 10 20 10 2
7. BAC + CHG (3% + 1 %) 10 10 20 50 20 5
8. BTC + CHG (3% + 1 %) 10 20 20 25 25 10
9. ATAB + CHG (3% + 1%)
25 10 10 50 10 2
10. Domiphen bromide + CHG
(3% + 1 %) 25 25 25 50 25 10
11. CPC+ CHG
(3% + 1%) 5 5 10 20 10 1
Table-2 summarizes the LD50 of Quaternary amine (QUAT) formulations of the present disclosure on different algal pests.
Table-2
S.No. Formulation LD 50 for different grazers/predators (ppm)
Time
(hrs) Conc
(ppm) Time
(hrs) Conc
(ppm) Time
(hrs) Conc
(ppm) Time
(hrs) Conc
(ppm)
1. Benzalkonium chloride (BAC) 24 2 12 1 12 2 12 1
2.
Benzethonium chloride (BTC) 24 0.5 12 0.5 12 2 12 0.5
3. Cetrimide (ATAB)
24 1 12 0.5 12 2 12 0.5
4. Domiphen bromide (DB) 24 1 12 0.5 12 2 12 0.5
5. Cetylpyridinium chloride (CPC)
24 0.5 24 0.5 12 2 12 0.5
6. Dichlorohexidine gluconate (CHG)
12 2 12 2 NE 5 12 1
7. BAC + CHG
(3% + 1 %) 12 1 12 0.5 12 2 12 0.25
8. BAC + CHG
(3% + 0.6%) 12 2 12 2 12 2 12 0.25
9. BTC + CHG
(3% + 0.3%) 12 3 12 2 12 4 12 0.5
10. BTC + CHG
(3% + 1 %) 12 0.25 12 0.25 12 1 12 0.25
11. BTC + CHG
(3% + 0.6 %) 12 1 12 0.5 12 2 12 0.25
12 BTC + CHG
(3% + 0.3%) 12 2 12 1 12 2 12 0.5
13 ATAB + CHG
(3% + 1%) 12 1 12 1 12 2 12 0.25
14 ATAB + CHG
(3% + 0.6%) 12 2 12 1 12 2 12 0.25
15 ATAB + CHG
(3% + 0.3%) 12 3 12 2 12 4 12 0.5
16 Domiphen bromide + CHG
(3% + 1%) 12 0.25 12 0.25 12 1 12 0.1
17 Domiphen bromide + CHG
(3% + 0.6%) 12 0.5 12 0.5 12 2 12 0.25
18 Domiphen bromide + CHG
(3% + 0.3%) 12 2 12 2 12 4 12 1
19 CPC+ CHG
(3% + 1%) 24 0.25 24 0.25 24 1 12 0.1
20 CPC+ CHG
(3% + 0.6%) 24 0.25 24 0.25 24 1 12 0.25
21 CPC+ CHG
(3% + 0.3%) 24 0.5 24 0.5 24 2 12 0.5
Note: NE-Not Effective
The effect of the formulation of the present disclosure is illustrated in Figures 1 to 6 of the accompanying drawing which is self-explanatory.

TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of large scale production of algae with effective and economical control of pests.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.