Bioremediation technology for insecticide residues in horticulture

• ORICA Australia Pty Ltd, Australia
• University of the Philippines at Los Banos, Philippines
• University of the Philippines, Diliman, Philippines

The use of chemical pesticides in the world's agricultural systems continues to grow. In 1998, the sale of agricultural pesticides in the Philippines was worth about A$70 million. In the same year in Australia, factory sales of pesticides reached nearly A$1.3 billion. Horticulture (along with cotton) is a major user of pesticides in Australia. Without pesticides it would be hard to meet consumer expectations of quantity and quality.

However, the remains of pesticides on the harvested product are a cause for concern in two ways. The first is direct toxicity to the consumer. This only occurs with very high concentrations of residue; even at low levels, though, there may be sub-clinical changes that can build up into symptoms over prolonged periods of exposure. Secondly, consumer pressure is driving many countries to become increasingly stringent about the concentration of residues on imported produce. For a country to export successfully to major markets like North America, Japan and Europe, its produce must satisfy these regulatory demands for minimal residue contamination.

Pollution of the natural environment is the other reason for concern over contamination. The main issue is pesticides in waste waters. Fish and invertebrates can be affected and, at higher levels, there are again human health concerns. Soil can also be contaminated. In addition, proven contamination of the environment is indirectly detrimental to the growers themselves because it is likely to affect their ongoing 'right to operate' and cause hostility to the industry.

CSIRO Entomology has developed enzyme-based technology that can remove residues of some key organophosphate (OP), carbamate and pyrethroid insecticides from drainage water and the surface of harvested commodities. The enzymes used, usually isolated from bacteria living in pesticide-contaminated soils, can break down the pesticides into essentially non-toxic compounds. CSIRO and Orica Pty Ltd are commercialising this.

The idea of this project is to develop protocols for applying the current suite of enzymes, after harvest, on four major crops. This will take place in the Philippines and Australia.

The project aimed to further develop existing Australian bioremediation technology in order to remove pesticide residues from the surfaces of horticultural crops.

The crops initially chosen were tomatoes, bananas, mangoes and eggplants - all major crops in the Philippines and elsewhere in the region. The first three are also major horticultural products in Australia. Eventually work was undertaken on eggplant, tomato, mango and bitter gourd but not banana.
The project transferred existing technologies and enzymes for OP and carbaryl breakdown to the University of the Philippines. (Carbaryl is part of the carbamate chemical family.) The team then worked to develop robust implementation processes for OP degradation on tomatoes and eggplants and OP/carbaryl degradation on mangoes and bananas.
The second main objective of the project was to develop an enzyme for breaking down the pyrethroid deltamethrin. Scientists collected soil exposed to deltamethrin from sites in Australia. Bacteria from the samples were isolated and tested and the most promising types used for enzyme development. The new enzyme was biochemically characterised and the gene (or genes) encoding it were cloned. This enzyme and the existing pyrethroid enzymes were then transferred to the Philippines. The team then sought to develop suitable implementation protocols for the breakdown of pyrethroid on eggplant and tomato.

The project made progress in the development of application protocols for enzymatic remediation of pesticide residues; it did not fully develop application protocols.
During the project, choice of commodity was restricted by need to use product with nil or known residue background. The development of enzymes for surface residue remediation has been baseline work and it was thus ambitious to consider that a medium project could develop full 'application protocols'. Critically the project has produced sufficient data and indicated sufficient potential for the use of the enzymes on fruit for the commercial partner, Orica to maintain an interest in further developing the products for fruit remediation.
The project also made progress towards the development of a remediation enzyme for certain larger pyrethroids but the process is not complete. Specifically the CSIRO team have detected 13 variants of the blowfly E3 esterase which show potential for degradation of Type II pyrethroids such as deltamethrin and cypermethrin.
CSIRO will continue to progress this component of work beyond the life of the project to try to further boost activity of most promising variants. Commercial partner Orica is currently scaling up fermentation and conducting formulation research on this class of enzyme ahead of laboratory-scale proof-of-concept experiments.
The first commercial product emerging from the research was launched by Orica Watercare at the 4th International Crop Science Congress, held in Brisbane in September 2004. The product, the first in the LandguardTM series, degrades organophosphates. The launch was complemented at the Congress by a CSIRO poster presentation in which ACIAR's contribution was acknowledged. Orica Watercare reports considerable interest in LandguardTM, both from the scientific community and from farmers.
However, as this project did not specifically focus on water cleanup any such benefit can only be indirectly attributed to this project. The CSIRO Bioremediation program is to be part of a major new research centre announced by the Australian Government in the 2005-2006 budget.