Mutation breeding of high 4-androstene-3,17-dione-producing Mycobacterium neoaurum ZADF-4 by atmospheric and room temperature plasma treatment

Steroid medication is used extensively in clinical applications and comprises a large and vital part of the pharmaceutical industry. However, the difficulty of separating 4-androstene-3,17-dione （AD） from 1,4-androstadiene- 3,17-dione （ADD） restricts the application of the microbial transformation of phytosterols in the industry. A novel at- mospheric and room temperature plasma （ARTP） treatment, which employs helium as the working gas, was used to generate Mycobacterium neoaurum mutants producing large amounts of AD. After treatment of cultures with ARTP, four mutants were selected using a novel screening method with a color assay. Among the mutants, M. neoaurum ZADF-4 was considered the best candidate for industrial application. When the fermentation medium contained 15 g/L phytosterols and was cultivated on a rotary shaker at 160 r/min at 30 ~C for 7 d, （6.28＋0.11） g/L of AD and （0.82＋0.05） g/L of ADD were produced by the ZADF-4 mutant, compared with （4.83＋0.13） g/L of AD and （2.34＋0.06） g/L of ADD by the original strain, Iv~. neoaururn ZAD. Compared with ZAD, the molar yield of AD increased from 48.3% to 60.3% in the ZADF-4 mutant. This result indicates that ZADF-4 may have potential for industrial production of AD.

Improving vanadium extraction from stone coal via combination of blank roasting and bioleaching by ARTP-mutated Bacillus mucilaginosus

In order to improve leaching efficiency of vanadium from stone coal,the combination of blank roasting and bioleaching using Bacillus mucilaginosus(B.mucilaginosus)mutants was evaluated.The atmospheric and room temperature plasma(ARTP)technique was used to generate B.mucilaginosus mutants.The results showed that a mutant B.mucilaginosus BM-50,after ARTP irradiation for 50 s,had the highest acid production.The total content of the organic acid produced by B.mucilaginosus BM-50 was nearly doubled compared with the wild strain after 2 days.After 20 days,vanadium leaching rate with B.mucilaginosus BM-50 reached 18.2%,which was improved compared with the original bacteria(15.3%).A pretreatment via blank roasting for stone coal further improved the vanadium dissolution by bioleaching,namely,68.3%vanadium was extracted,which was much higher than that without blank roasting.It is shown that bioleaching by bacterial mutants by ARTP irradiation combined with blank roasting has great potential for improving vanadium recovery from low-grade vanadium bearing stone coal.