Jinlin Zhang

Degradation of nicosulfuron by Bacillus subtilis YB1 and Aspergillus niger YF1

The optimal degrading conditions for the nicosulfuron degradation by Bacillus subtilis YB1 and Aspergillus niger YF1, and site of their action on nicosulfuron were studied. The results showed that the degradation efficiency of free cells of B. subtilis YB1 and A. niger YF1 was respectively 87.9 and 98.8% in basic medium III containing 2 mg/l of nicosulfuron after inoculation with 1 ml of culture containing 2.3 × 107 CFU ml−1 and incubation for 5 days at 35°C. Moreover, the degradation rate of nicosulfuron by the mixture of microorganisms was much higher than for every of them taken separately in the same conditions. The mass spectrometric analysis of the products degraded by B. subtilis YB1 revealed that the sulfonylurea bridge in nicosulfuron molecule had been broken. Extracellular (EXF) and endocellular (ENF) fractions obtained from bacterium and fungus were tested for the ability to degrade nicosulfuron. The degradation efficiency of fractions extracted from B. subtilis YB1 was 66.8% by EXF and 15.8% by ENF, but neither EXF nor ENF extracted from A. niger YF1 had the activity of degrading nicosulfuron.

The Extraction, Isolation and Identification of Exudates from the Roots of Flaveria bidentis

Large amounts of ”Flaveria bidentiss” root culturing solution were obtained by using DFT (deep flow technique) equipment and these solution which was vacuum concentrated (10, 20 mg mL^(-1)) can have a certain inhibition on ”Triticum aestivum”, ”Cucumis sativus”, ”Raphanus sativus”, ”Amaranthus retroflexus”, ”Setaria viridis”, ”Chenopodium album”, ”Echinochloa crusgalli” and ”Chloris virgata”. This outcome suggested some active compounds in the root exudates of ”Flaveria bidentis” can inhibit the germination, seedling elongation and root length. The dichloromethane extract of root exudates was identificated by GC-MS, and 29 kinds of compounds, including esters, hydrocarbons, ketones, thiazole, amines, etc. were obtained and the phthalate n-octyl ester, phthalate 2-ethylhexyl ester were proved to be allelochemicals. The culturing solution of root exudates was separated through the resin column and silica gel column and a component inhibiting seedling height, root length and fresh weight of wheat was got. There were 6 kinds of organic compounds in this component including dioctyl phthalate, 1,2-phthalate, mono(2-ethylhexyl) ester by GC-MS.

Optimization and Characterization of Nicosulfuron-Degrading Enzyme from Bacillus subtilis Strain YB1

Abstract A strain of Bacillus subtilis strain YB1, isolated and preserved in our lab., showed a high nicosulfuron-degrading activity. Optimization of culture conditions on production of nicosulfuron-degrading enzyme from Bacillus subtilis strain YB1 was carried out through mono-factor experiments. The characterization of degrading enzyme(s) was studied in this paper. The results showed that B. subtilis YB1 can use nicosulfuron as sole carbon source under aerobic condition. The key enzyme(s) involved in the initial biodegradation of nicosulfuron was localized to extracellular proteins and showed to be induced expressed. Enzyme-specific activity was up to 89.34 U mg −1 at pH 8.0 and 30°C, incubation for 96 h, inoculum 4.5×10 8 CFU mL −1 in Luria-Bertani liquid medium with nicosulfuron of 40 mg L −1 . The maximum degradation rate of extracellular crude enzymes on nicosulfuron was 66% at pH 9.0, 35°C in the enzymatic reaction system with nicosulfuron of 5 mg L −1 . This degrading enzyme(s) was sensitive to high temperature, but kept high activity under alkaline conditions.

Isolation and Structural Speculation of Herbicide-Active Compounds from the Metabolites of Pythium aphanidermatum

Natural herbicides, or environment-friendly bioherbicides have been attracted more and more attentions. Isolation and structural identification of natural herbicide-active compounds from plant pathogens has been proved to be an effective approach for novel lead discovery of the pesticide development. In this study, the metabolites of the mutant strain PAM1, which obtained from PA1 of Pythium aphanidermatum (Eds.) Fitzp by ultraviolet radiation were separated and identified by HPLC, NMR, and IR. The results revealed that three active compounds including 4-hydroxy-3-methoxycinnamic acid and two indole derivatives, exhibited inhibition activity on the elongation of radical and coleoptile of Digtaria sanguinalis (L.) Scop.

The Herbicidal Activity of Mutant Isolates from Botrytis cinerea

Fifteen mutant isolates were obtained by ultraviolet mutation from parent isolate Botrytis cinerea BC-4. Among them three mutant isolates, BC4-1, BC4-2, and BC4-15, showed strong herbicidal activity. BC4-1 showed maximum herbicidal activity for inhibition of germination and growth of Digitaria sanguinalis L. and Amaranthus retroflexus L. The results also showed that herbicidal activity was influenced by differing pH of PD media, with pH value of 4.0 being the optimum. The crude toxin was extracted using chloroform, petroleum ether, and ethyl acetate, respectively, and the ethyl acetate extracts showed the strongest inhibitory activity on the germination and growth of D. sanguinalis L. and A. retroflexus L. Using HPLC, one fraction with an absorption peak at 271 nm was separated from the crude toxin. This fraction could strongly inhibit the growth of D. sanguinalis L. at a concentration of 100 mg L^(-1) and could completely inhibit the seed germination of D. sanguinalis L. and A. retroflexus L. at a concentration of 50 mg L^(-1).

Purification and cloning of nicosulfuron-degrading enzymes from Bacillus subtilis YB1

The nicosulfuron-degrading enzymes from Bacillus subtilis strain YB1 were purified and their genes were cloned. The proteins of bacterial culture filtrate were precipitated with ammonium sulfate or acetone. The extracellular proteins concentrated by acetone were purified from DEAE-Sepharose Fast Flow chromatography. The four protein peaks eluted from DEAE-column were separated and purified by native PAGE. Three components (P1-1, P3-2, P4-3) had nicosulfuron-degrading activity, and component P4-3 degradated 57.5% of this compound. The molecular weights of the components were 33.5, 54.8 and 37.0 kDa, respectively. The amino acid sequences of nicosulfuron-degrading enzymes from B. subtilis YB1 were determined by MALDI-TOF-MS, indicating these enzymes as manganese ABC transporter, vegetative catalase 1 and acetoin dehydrogenase E1, respectively. Using PCR amplification, genes 918, 1428, 1026 bp in size were detected for the enzymes studied.