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Biotechnology has provided environmentally sound solutions to problems faced by the papermaking industry. Kuhad attribute the importance of biotechnology to its potential for more specific reactions, less environmentally deleterious processes, energy savings, and capacity to be used in place of non-biological processes.
Biological products have long played a critical role in paper mill sludge treatment and effluent clarification. Newer biological applications include targeting organic contaminants in thermo-mechanical pulp (TMP) mill white water for fungal treatment and de-chlorinating kraft bleach effluents with Rhizopus oryzae.
Enzyme preparations are effective in curbing bacterial growth in mill process water and inhibiting the build-up of biofilms. The idea that microorganisms and their enzymes can successfully replace or supplement conventional chemical processes in the pulp and paper industry is gaining acceptance in the United States, following the lead of Scandinavia and Canada. Enzyme preparations have moved from laboratory exploration to mill settings for various industrial applications.
Biotechnology providing new and exciting cost- effective alternatives to complement rather than totally replace traditional technologies. Extensive reviews of the use of enzymes for bleaching, deinking, pitch removal and drainage enhancement illustrate the broad interest in and potential of biotechnology.
Relining energy can be significantly reduced if wood chips are pre-treated with fungal inoculate in the bio-pulping process or with bacterial inoculate to reduce pitch. All of these technologies have advanced to mill-scale trials.
Applications that have been successfully transferred to commercial use include xylanases for bleach boosting, celluloses for improved drainage, lipases for pitch removal, and cellulose- hemicellulose mixture for deinking.
Sustainable Forestry:
‘Selection and hybridisation-Develop optimum natural species and hybrids for use in local conditions. Genetic engineering and tree breeding-Modify gene structure and improve genetic selection programmes to increase growth rates, improve insect and disease resistance, improve fiber quality, and enhance environmental adaptability.
Following are two emerging applications of biotechnology for forest trees:
i. Genetically altering trees for improved forest health through a higher tolerance for pest infestation, disease resistance, and severe climatic conditions, as well as for enhanced properties such as accelerated growth and unproved papermaking qualities (i.e., reduced pitch or lignin content), and
ii. Phytoremediation of contaminated soil, air, and water.
Recent advances in gene mapping techniques permit researchers to identify trees with desired traits (e.g., fast growth, resistance to disease or cold temperatures) that can be used to breed improved species by conventional means.
Mapping permits researchers to focus on specific genes and their components on the molecular level. Identification of gene function permits gene manipulation and the introduction of new and desirable traits not available in the breeding population.
Ultimately, such mapping should permit isolation of desired tree genes that could be engineered directly into target tree species. New techniques for identifying gene markers facilitate the location of desired genes useful for tree breeding. Once potentially valuable genes are located, they can be cloned and improved strains of the same or other tree species can be created.
Cloning permits replication of genetically engineered trees and enables mass production of embryos of identical trees that contain one or more value-added traits. Embryos are inserted into manufactured seed and the seeds are sown following conventional culture in a nursery.
Identical trees are advantageous in ensuring a uniform raw material that is relatively predictable in its requirements for conversion to pulp and paper. Another approach to genetic altering of trees, which utilises “antisense constructs” to inhibit enzyme production needed for lignin synthesis, has been used by Belgian researchers in their work to minimise the lignin content of trees.
Phytoremediation:
Trees are already used for wastewater clean-up, for site stabilisation, and as barriers to subsurface flow of contaminated groundwater. Trees are ideal remediates because they are fast-growing perennial plants with extensive root systems and high transpirational rates.
Their large biomass is advantageous because it permits higher tolerance for toxic materials and has the capacity for accumulating contaminants. Because plant remediation is done in situ, it has the potential to be substantially less expensive than alternative technologies used for detoxification.
The main methods of phytoremediation are:
i. Decontamination, in which the amount of toxic pollutants in the soil is significantly reduced or eliminated, and
ii. Stabilisation and containment in which plants and their associated micro-flora do not remove contaminants but rather alter the soil chemistry and sequester, reduce, or eliminate the environmental risk of the toxin.
Work is underway to screen tree species for their ability to tolerate, take up, translocate, sequester, and degrade organic compounds and heavy metal ions. Clonal propagation and genetic engineering techniques already exist for a number of species, which opens the door to the creation of tree “remediation” cultivars.
This in situ use of plants to stabilise, remediate, and restore a commentated site is referred to as phytoremediation. All plants have the ability to accumulate metals essential for their growth and development; these metals include iron, manganese, zinc, copper, magnesium, molybdenum, and possibly nickel.
Certain plants accumulate heavy metals that have no known biological function: these metals include cadmium, chromium, lead, cobalt, silver, selenium, and mercury. However, significant accumulation of heavy metals is usually toxic to most plants. For some time, botanists have been aware that certain tree species are endemic to soils containing high metal content.
Identification of heavy metal tolerance by some plants has led to research that exploits this characteristic for removing metal contaminants by establishing selected vegetation on contaminated soil; these plants are called “accumulating” plants. A specific example of this technology is the development of a transgenic yellow poplar developed for remediating mercury-contaminated soil.
Hyper-accumulating plants promise effective, inexpensive remediation of soil, sediment, and groundwater. Whereas metal-tolerant plants exclude toxic metal ions from uptake, hyper-accumulating plants take up high amounts of toxic metals and other ions. An exciting possibility of applying biotechnology lies in identifying a tree species with the ability to tolerate or accumulate toxic substances such as heavy metals or organic compounds.
Once identified, this tree species could be introduced in contaminated areas. Furthermore, genetic modification could accelerate remediation by making the tree a hyper-accumulator, by adapting its growth to diverse climatic conditions, or by enabling faster growth.
Phytoremediation is based on root uptake of contaminants and storage in the plant or partial/complete degradation to less toxic compounds. This type of remediation could promote degradation of organic pollutants by increasing soil organic carbon content or by releasing enzymes that promote microbial activity through the plant roots.
Phytoremediation could be useful in ameliorating heavy metals and organic compounds such as 2, 4, 6-trinitrotoluene (TNT), trichloroethylene (TCE), benzene, toluene, xylene, and ethyl-benzene.
The benefits of phytoremediation include the fact that it is done in situ and that it is a passive, solar-driven “green” technology. Roots are exploratory, liquid-phase extractors that can find, alter, and/or translocate elements and compounds against large chemical gradients. This technology is most effective on sites containing a low level of contamination that are widely dispersed over a large area in the upper surface of the soil.
Phytoremediation can work side by side with site restoration with minimum site disruption. Additionally, plant biomass can be harvested to remove contaminants from the site and trees will re- sprout without disturbing the site. In sites where a valuable heavy metal has accumulated, it may be possible to reclaim the metal from the harvested tree.
Phytoremediation techniques are less expensive than ex situ methods, but they require a long time to work. Long-term site remediation and stabilisation using trees makes remediation and restoration synonymous, which lowers costs and is compatible with public objectives. The most appropriate type of remediation for a specific site depends on the degree of pollution and the type of toxic material.
More intensive remedies are required for localised, highly contaminated sites. Conventional soil remediation methods are more suitable for these sites. These methods typically involve excavation of contaminated soil followed by extraction of the toxin. This ex situ technique is usually extremely expensive.
Toxic metal contamination of soil and groundwater is a major environmental and human health problem for which affordable, effective solutions are urgently needed. In agricultural areas, sites are frequently contaminated by a build-up of residual herbicides Atrazine, a commonly used agricultural herbicide, has been the focus of bioremediation researchers.
Research with hybrid poplars has resulted in soma-clonal variants that tolerate lethal dosages of herbicides. Another aspect of engineered tolerance, pesticide and herbicide resistance is especially interesting.
If trees could be engineered to be more tolerant of the ubiquitous chemicals in soils, substantially higher yields of forest trees could be realised.
Other possibilities for phytoremediation range from removing concentrations of naturally occurring selenium solubilised in irrigation water and accumulated in surrounding groundwater to using genetically altered eucalyptus trees for absorbing and metabolising air pollutants. The possibilities seem to be limited only by the imagination of researchers and the toxic material present.