With the development of science and technology, yeast has been applied more and more, among which, using yeast technology to repair contaminated soil is an effective method.Yeast is rich in resources, has a variety of metabolic pathways and relatively mature operation methods, and has a great potential to repair multiple contaminated soil.Yeast technology has made great breakthroughs in eliminating pesticides, herbicides, pahs and heavy metals in contaminated soil.
Remediation of soil contaminated by pesticides
Organochlorine pesticides mainly include hex66 (HCH), 223 (DDT), chlordane and heptachlor, which are highly toxic pesticides used on a large scale in the 20th century. They are highly toxic, difficult to degrade and have a long metabolic cycle.For example, the longest time required for HCH to be decomposed 95% in soil is about 20 years. DDT's chemical properties are also relatively stable. Although DDT has been banned for nearly 30 years, there are still large amounts of residues in the environment.Organochlorine pesticides have certain volatility and strong lipid solubility, which can be enriched in organisms through the food chain and cause harm to the ecosystem and human health.
Yeast degradation plays an important role in the removal of organochlorine pesticides.Taking HCH as the sole carbon source, three strains of bacteria, namely bacillus, achromycetes and pseudomonas, were obtained successively. The degradation rates of total HCH were 59.6%, 56.9% and 56%, respectively, and the degradation rates of HCH were 55.9%, 57.6% and 56.9%, respectively.Some experts selected a strain of oligomonas D1 from ddt-contaminated soil, and its degradation rate of DDT for 10d was 69%.
Organophosphorus pesticides are the main types of pesticides nowadays, which have great influence on soil respiration and other ecosystems.Organophosphorus pesticides mainly include methamidophos, dimethoate, chlorpyrifos and dichlorvos.There are many studies and reports on the degradation of organophosphorus pesticides by yeast at home and abroad. At present, a variety of degradation strains have been isolated, a variety of degradation enzymes have been purified, and many degradation enzyme genes have been cloned and expressed.