OPTIMIZATION OF PARAQUAT DEGRADATION WITH MICROBIAL CONSORTIUM FROM CONTAMINATED SOIL USING STATISTIC METHOD

Paraquat is one of non-selective herbicides, widely used in Thailand and other countries that can be used to prevent and mitigate problems with weeds that have become resistant. It has a broad spectrum of weed knockdown herbicide which can be easily distributed in an aquatic environment due to its high solubility in water. The aim of the research is to study the optimization condition for biodegradation of paraquat by microbial consortium using an orthogonal array design in culture media. The microbial consortium which can degrade paraquat were isolated from cassava rhizosphere soil with a historic area of using paraquat in Kalasin, Thailand. Analysis of the 16S rDNA gene sequences compared with the database in Gen Bank demonstrated that microbial consortium showed the similarity with Sphingomicrobium marinum (97%), Ferrovibrio xuzhouensis (93%), Azospirillum lipoferum (93%), Altererythrobacter xinjiangensis (94%), Xanthobacter autotrophicus (92%) and Azospirillum amazonense (99%). To achieve the biodegradation experiments, orthogonal arrays design was investigated, with the three independent variables: glucose concentration (1-20 g/L), paraquat concentration (10-100 mg/L) and inoculum concentration (110%). The biodegradation consortium was done triplicate in 250 mL Erlenmeyer flask at 30°C 150 rpm for 35 days. Paraquat biodegradation was reported as biodegradation percentage. The results demonstrated that the optimum concentrations of glucose, paraquat, and inoculum for paraquat biodegradation were 1 g/L, 10 mg/L, and 5%, respectively. The paraquat removal efficiency of 95.69% was achieved under the optimal condition.